CA1225149A - Method and circuit arrangement for simulating a multi- colored reproduction on a color monitor - Google Patents
Method and circuit arrangement for simulating a multi- colored reproduction on a color monitorInfo
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- CA1225149A CA1225149A CA000470818A CA470818A CA1225149A CA 1225149 A CA1225149 A CA 1225149A CA 000470818 A CA000470818 A CA 000470818A CA 470818 A CA470818 A CA 470818A CA 1225149 A CA1225149 A CA 1225149A
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Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N1/00—Scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission; Details thereof
- H04N1/46—Colour picture communication systems
- H04N1/56—Processing of colour picture signals
- H04N1/60—Colour correction or control
- H04N1/603—Colour correction or control controlled by characteristics of the picture signal generator or the picture reproducer
- H04N1/6052—Matching two or more picture signal generators or two or more picture reproducers
Abstract
ABSTRACT
A method and apparatus for isochromatic simulation of a multi-colored reproduction on a color monitor. Before simulation, colors are generated on the color monitor and are matched to corner colors of a printed color chart or the like by measuring or visual comparison. The color values required for the chromatically coinciding generation of the corner colors on the color monitor are measured and allocated to color separation values of the corner killers The color values required for venerating intermediate colors are calculated upon consideration of the printing process of the multi-colored reproduction and are allocated to the corresponding color separation values of the intermediate colors. During the simulation, the color separation values of the multi-colored reproduction are output, modified according to a gradation curve, and transformed into the color values for driving the color monitor in accordance with the previously identified allocations.
A method and apparatus for isochromatic simulation of a multi-colored reproduction on a color monitor. Before simulation, colors are generated on the color monitor and are matched to corner colors of a printed color chart or the like by measuring or visual comparison. The color values required for the chromatically coinciding generation of the corner colors on the color monitor are measured and allocated to color separation values of the corner killers The color values required for venerating intermediate colors are calculated upon consideration of the printing process of the multi-colored reproduction and are allocated to the corresponding color separation values of the intermediate colors. During the simulation, the color separation values of the multi-colored reproduction are output, modified according to a gradation curve, and transformed into the color values for driving the color monitor in accordance with the previously identified allocations.
Description
2~9 SPECIFICATION
The invention relates to the field of electronic no-production technology for multi-colored printing and relates to a method of simulating a multi-colored reproduction on a color monitor in order to execute a color evaluation and color correction of the anticipated printing result before the actual printing process. The invention also relates to a circuit arrangement referred to as a color viewing apparatus.
In the electronic reproduction of color originals, three primary color value signals, which are a measure for the color components red, Green and blue of the scanned pie-lure elements, are acquired in a color scanner by point-by-point and line-by-line trichromatic scanning of the original and opto-electronic conversion of the scan light. A color correction computer corrects the measured color value signals and generates four color separation signals for the color separations "yellow", "magenta", "cyan", and Black in the case of four-color printing. During printing, the color separation signals indicate the required quantities of yellow, magenta, cyan, and black ink. The printing forms for print-in are produced from the color-corrected separation signals.
The superimposed printing of the printing forms inked with the four inks then occurs on the impression paper in impression printing presses.
Color viewing apparatus wherein the anticipated printing result is simulated by simulating the printing pro-cuss on a color monitor, are in use in order to monitor the anticipated printing result even before the production of the printing forms and in order to correct if necessary. So-called color converters or print simulation computers are I
employed for printing simulation, these converting the color separation signals into drive signals for the color monitor upon consideration of the print paramours such that the color picture of the monitor conveys the same chromatic impression as the anticipated multi-color printing on the impression paper.
US. Patent 3,128,333 discloses a color converter in which the color separation signals are converted into corresponding drive signals for the color monitor by an analog signal processing. The known color converter, however, has the disadvantage that a reproduction quality of a multi-color reproduction, that is only averaged over the entire color space, can be achieved in the representation of party colors on the color monitor.
It is an object of the invention to specify a method and a circuit arrangement for simulating a multi-color reproduction on a color monitor with which the farthest reaching chromatic coincidence between monitor color picture and later multi-color reproduction is achieved 80 that a high-grade and reliable statement regarding the expected reproduction quality is possible.
According to the invention, color signal values are prescribed, the colors corresponding to the prescribed color signal values generated on the color monitor. The generated monitor colors are matched to corner colors of a print color space by changing the color signal values so that the print corner colors have been printed under conditions of the multi-color reproduction. The color value triads r, g, b required for the chromatically coinciding generation of the corner colors on the color monitor are identified given I
12~ 19 consideration of a non-linear relationship between radiation density values of individual phosphors of the color monitor and the color values. Fox every corner color, the identified color v~lU2 triad r, g, b is allocated to a corresponding triad Y*, M*, C* of color separation values of three chromatic color separations of the corner color. Color value triads r, g, b for intermediate colors of the print color space lying between the corner colors required for chromatically coin-aiding generation of the intermediate colors on the color monitor are respectively calculated from triads Y, M, C of the three chromatic color separations given consideration of the reproduction process for the multi-color reproduction. For every intermediate color, the calculated color value triad r, g, b is allocated to the corresponding triad Y, M, C of color separation values of the three chromatic color spear-anions of the intermediate color. During simulation of thy multi-colored reproduction color separation values Y, M, C0 K
of the three chromatic color separations and of a black separation of the multi-colored reproduction are called in and are modified according to a reproduction gradation curve employed in the later to occur multi-color reproduction.
The previously allocated color value triads r, g, b are ; output instead of color separation value triads Y', M', C' of the three chromatic color separations of the multi-colored reproduction. The output color value triads r, g, b are combined with the modified color separation values K' of the black separation to form corrected color value triads r', g', b'. The corrected color value triads r', g', b' are converted into video drive values rev go b' for the color monitor,
The invention relates to the field of electronic no-production technology for multi-colored printing and relates to a method of simulating a multi-colored reproduction on a color monitor in order to execute a color evaluation and color correction of the anticipated printing result before the actual printing process. The invention also relates to a circuit arrangement referred to as a color viewing apparatus.
In the electronic reproduction of color originals, three primary color value signals, which are a measure for the color components red, Green and blue of the scanned pie-lure elements, are acquired in a color scanner by point-by-point and line-by-line trichromatic scanning of the original and opto-electronic conversion of the scan light. A color correction computer corrects the measured color value signals and generates four color separation signals for the color separations "yellow", "magenta", "cyan", and Black in the case of four-color printing. During printing, the color separation signals indicate the required quantities of yellow, magenta, cyan, and black ink. The printing forms for print-in are produced from the color-corrected separation signals.
The superimposed printing of the printing forms inked with the four inks then occurs on the impression paper in impression printing presses.
Color viewing apparatus wherein the anticipated printing result is simulated by simulating the printing pro-cuss on a color monitor, are in use in order to monitor the anticipated printing result even before the production of the printing forms and in order to correct if necessary. So-called color converters or print simulation computers are I
employed for printing simulation, these converting the color separation signals into drive signals for the color monitor upon consideration of the print paramours such that the color picture of the monitor conveys the same chromatic impression as the anticipated multi-color printing on the impression paper.
US. Patent 3,128,333 discloses a color converter in which the color separation signals are converted into corresponding drive signals for the color monitor by an analog signal processing. The known color converter, however, has the disadvantage that a reproduction quality of a multi-color reproduction, that is only averaged over the entire color space, can be achieved in the representation of party colors on the color monitor.
It is an object of the invention to specify a method and a circuit arrangement for simulating a multi-color reproduction on a color monitor with which the farthest reaching chromatic coincidence between monitor color picture and later multi-color reproduction is achieved 80 that a high-grade and reliable statement regarding the expected reproduction quality is possible.
According to the invention, color signal values are prescribed, the colors corresponding to the prescribed color signal values generated on the color monitor. The generated monitor colors are matched to corner colors of a print color space by changing the color signal values so that the print corner colors have been printed under conditions of the multi-color reproduction. The color value triads r, g, b required for the chromatically coinciding generation of the corner colors on the color monitor are identified given I
12~ 19 consideration of a non-linear relationship between radiation density values of individual phosphors of the color monitor and the color values. Fox every corner color, the identified color v~lU2 triad r, g, b is allocated to a corresponding triad Y*, M*, C* of color separation values of three chromatic color separations of the corner color. Color value triads r, g, b for intermediate colors of the print color space lying between the corner colors required for chromatically coin-aiding generation of the intermediate colors on the color monitor are respectively calculated from triads Y, M, C of the three chromatic color separations given consideration of the reproduction process for the multi-color reproduction. For every intermediate color, the calculated color value triad r, g, b is allocated to the corresponding triad Y, M, C of color separation values of the three chromatic color spear-anions of the intermediate color. During simulation of thy multi-colored reproduction color separation values Y, M, C0 K
of the three chromatic color separations and of a black separation of the multi-colored reproduction are called in and are modified according to a reproduction gradation curve employed in the later to occur multi-color reproduction.
The previously allocated color value triads r, g, b are ; output instead of color separation value triads Y', M', C' of the three chromatic color separations of the multi-colored reproduction. The output color value triads r, g, b are combined with the modified color separation values K' of the black separation to form corrected color value triads r', g', b'. The corrected color value triads r', g', b' are converted into video drive values rev go b' for the color monitor,
-3-~L22S~
On The Drawings-Figure l is a schematic circuit arrangement for a color viewing apparatus;
Figure 2 is a graphic illustration of a printing color space; and Figure 3 is an advantageous development of a circuit arrangement of the invention.
Figure 1 shows an illustrative embodiment of a air-cult arrangement for simulating a multi-color reproduction on a color monitor for a color evaluation and color correction of an anticipated multi-color reproduction before a printing process. This is referred to below as a color viewing apparatus.
The color viewing apparatus is essentially composed of a signal source 1, of a transformation circuit 2, of a color monitor 3, and of a clock generator 4.
The signal source 1 generates digital color swooper-lion values Ye M, C, and K for the color separations "yellow"
(Y), "magenta" (M), "cyan" (C) and "black" lo) of a color picture to be printed. The digital color separation values Y, M, C, and K are a measure for the required metered amounts of printing inks or for the size of the raster points, in percent. The digital color separation values have, for example, a word length of 8 bits, whereby "black" (100% raster point size) is allocated to the digital color separation value 0 and "white" (0% raster point size) is allocated to the digital color separation value 225. A total of 254 gray scale values are discriminated between "black" and "white".
The signal course 1 can contain an electronic color camera which generates measured color value signals I G, and I
B by a video-wise, point-by-point and line byline scanning of the color picture to be printed or to be represented on the color monitor 3.
An adjustable color correction stage following the color camera converts the measured color value signals R, G, and B into the color separation signals Y, M, C, and K
according to the laws of subtractive color mixing.
In the illustrative embodiment shown, the signal source 1 is composed of a full frame memory S, ox a correction stage 6, of an image repetition memory 7, and of an address controller 8. The digital color separation values Y, M, C, and K of a discrete image or of an already assembled printing page are deposited in the full frame memory 7. The color separation values Y, M, C, and K of a discrete image were generated, for example, in a color scanner. The combination of the color separation values of various discrete images to form the color separation values Jo of a printing page occurs according to a lay-out plan, for example by an electronic page make-up in an image processing system of the German OX 21 61 038, corresponding to US.
Patent 1,407,487. The color separation values required for the representation of the color picture or of a trimmed picture on the color monitor 3 from, for example, 512 x 512 picture elements, are selected or calculated from the entire detest of the full frame memory 5, and are loaded from there via the data busses 9 into the image repetition memory 7 which comprises a storage capacity for 512 x 512 color separation values corresponding to the number of picture elements. For the transmission of the color separation values, the address controller 8 calls the corresponding addresses in the full frame memory 5 and in the Ed SLY
image repetition memory 7 via the address busses 10 and 11l and generates the corresponding read clocks on control busses 12 and 13.
For the representation of the color picture on the color monitor 3, the address controller 8 cyclically calls in the addresses of the image repetition memory 7 via the address bus 10. The addressed color separation values Y, M, C, and K are read out line-by-line and picture-element-by-picture-element within every line with the assistance of the read clock ox the control bus 12, and are supplied via the data busses 14 to the transformation circuit 2. In the transformation circuit 2, the color separation values Y, M, C, and K are transformed into video drive signals rev go and by for the color monitor 3 on lines 15 such that the color picture displayed on the color monitor 3 conveys the.
same chromatic impression as the color picture printed on the impression paper under production run conditions.
The point-by-point and line-by-line recording of the color picture on the color monitor 3 occurs, for example, according to the line interlace method with 50 fields/sec in order to produce a flicker-free image. Based on the technique standard in television, the clock generator 4 generates the horizontal and vertical deflection signals as well as the line start pulses and picture start pulses on lines 16. The address controller 8 in the signal source 1 supplies cores-pounding horizontal and vertical sync pulses via lines 17 to the clock generator 4, so that the monitor recording is synchronized with the read operation of the color separation values from the image repetition memory 7.
The operator can now evaluate the displayed color picture and, when necessary, undertake color corrections by '~3"Z~
changing the color separation values Y, M, C, an K with the assistance of the correction stage 6 in the full frame memory : SO The color separation values Y, M, C, and K modified in the full frame memory 5 are automatically transferred into the image repetition memory 7, so that the color-corrected picture respectively appears on the color monitor 3.
Each of the color separation values quadruplets Y, M, C, and K supplied by the signal source 1 represents a color printed on the impression paper, referred to below as print color, which arises by superimposed printing of different proportions of the yellow, magenta, cyan, and black colors, and by subtractive color mixing. Each print .. . .. . .
; color can be identified by a triad of standardized color values XDr YE, and ED The video drive values rev- go and by are a measure for the luminance of the individual phosphors "red", "green" and "blue" of the color monitor 3.
Each triad of video drive values rev go and by therefore represents a color formed on the color monitor 3 by additive color mixing of the components red, green, and blue, said color being referred to below as a monitor color. Every monitor color can likewise be identified by a triad of -standardized color values EM, YE, and EM-- The transformation stage 2 is composed of a color generator 18, of gradation stages Audi, of a color con-: 25 venter 20, of linearization stages 21, and of digital-to-analog converters 22. The color converter in turn comprises an interpolation stage 23, a supporting value memory 24, an arithmetic stage 25, a measuring stage 26, as well as super-imposition stages 27.
In the gradation stages lea lid, the color swooper-lion values Y, M, C, and K are corrected into color 12~ Lo separation values Y', M', I and K' according to equation I first according to gradation curves if:
Y',M',C'~X' = f~(Y,MrC,R). (1) The print gradation curves if, also referred to as print characteristics, take the parameters of the printing process, the impression paper, as well as the true inks into consideration. The gradation stages Lydia are designed, for example, as laudably memories (Russ in which the print gradation curves if are stored.
The corrected color separation value Y', My, C', and K' are forwarded to the color converter 20. In the color converter 20, the triad of color values or', g', b') which is required for the representation of the isochromatic monitor color is generated for every quadruplet of corrected color separation values (Y',M',C',K') of a print color:
go Jo foe MUCK (2) In the color converter 20, only the color separation values Y', M', C' corrected in the gradation stages Lydia are forwarded via the data busses 28 to the input of the interpolation stage 23, whereas the color separation values K' corrected in the gradation stage lea for the black separation proceed via a data bus 29 directly to the super-imposition stages Z7. In accordance with equation (3), the interpolation stage 23 first outputs an allocated triad of color values r, g, and b required for isochromatic represent station for every triad of corrected color separation values YUMMY', and C', ire. without taking the black separation into consideration:
rub = f3(Y',M',C;). (3) I
In the illustrative embodiment shown tile allocation accord-in to equation (3) is advantageously calculated only for a supporting point network of the print color space deposited in the supporting value memory 24, whereas all allocations required for recording the color picture on the color monitor 3 are identified by continuous inter-pollution in the interpolation stage 23. Alternatively, the allocations can also be calculated before the recording of the color picture, and are calculated for all theoretically possible colors of the print color space. In this case, the interpolation stage 23 is replaced by a eon-despondingly larger allocator memory.
The color values r, g, and b output from the interpolation stage 23 arc joined in multiplicative fashion in the superimposition stages 27 to the color separation values K' for the black separ.ltioll in order to obtain the corrected color values r', g', and b' at the out-put of the color converter 20.
rub = f4(r,g,b) (4) The corrected color values r', g', and b' represent the monitor colors to be generated on the color monitor 3, but which are not achieved due to the monitor characteristics, i.e. due to the non-linear relation-ships between the radiation density values of the individual phosphors and the video drive values. For this reason, linear relationships must be produced by a so-called monitor linearization between the radiation density value of the red phosphor and the video drive values r', the radiation density value of the green phosphor, and the video drive values g', as well as between the radiation density value of the blue phosphor and the video drive values b'.
~L~25~ 9 This monitor linearization occurs since the color values r', g', and b' are converted into corresponding video drive values I go by in the linearization stages 21 based on the measure of the monitor characteristics. The linear-ration stages 21 are designed, for example, as laudably memories (Rams) in which the calculated video drive values I go by are digitally stored. The stored digital video drive values rev go by are converted into the analog video drive values rev, go and by on the lines 15 in the digital-to analog converters 22 which follow the linearization stages 21.
The monitor characteristics can be identified by a measurement of the radiation density at the color monitor as a function of the drive values. However, the monitor characteristics specified by the manufacturer of the color monitor can also be employed. In case the specified monitor characteristics are not exact enough, a correspondingly larger number of characteristic values could be identified by interpolation.
It is within the scope of the invention to already execute the calculation of the corrected color separation values Y', M', C', and K' in the gradation stages Lydia, the multiplicative combination of the color values r, g, and b with the corrected color separation values Al of the black separation and/or the linearization of the video drive values TV go and by before the representation of the color picture on the color monitor 3, and to take the corresponding cowlick-lotions into consideration in the detest of the supporting value memory 24 or of the allocator memory.
The function of the color viewing apparatus having been explained, the method for the identification of the ~L2;~5~4~3 color values r, g, and b required for a chromatically equip valet color picture representation dependent on the color separation values Yo-yo M', and C' for the supporting location network or for the supporting value memory 24 in the color converter 20 before actual operation of the color viewing apparatus shall be discussed. In this phase of operations, a changeover 30 is situated in the illustrated position, so that the color generator 18 is connected to the gradation stages Audi.
It is thus assumed that the gradation stages Lydia and the supporting value memory 24 function linearly at first, since the gradation stages Lydia as well as the supporting value memory 24 are loaded with linear functions In a first step, a calibration of the color monitor 3 to the brightest white (maximum picture white) and to the ; darkest black (maximum picture depth) is undertaken. It is guaranteed as a result of the white calibration that the color monitor 3 is illuminated with the brightest white when all color separation values Y=M=C=K=255 (rated white;
0% raster point size) or when the video drive values rev, go and by supplied to the color converter 20 are at maximum. For white calibration, the required color swooper-lion values are set in the color generator 18 with the assistance of the color regulators 31 "yellow", "magenta", "cyan", and "black", the monitor white thus generated being visually compared to a model original "picture white", for example to an art paper, and the operating parameters of the color monitor 3 being varied until the monitor white corresponds to the maximum picture white.
A following black calibration is intended to insure that the color monitor 3 generates the blackest black when ~:2~4g the color separation values Y=M=C=K=0 (picture black; lQ0~
roster point size) so when the video drive values rev glove and ho are at a minimum. The black matching occurs analog guzzle with a corresponding model original "black.
After the described calibration, those color value triads m, gnu and by which are required for isochromatic reproduction of the print colors Fun or of the multi-color reproduction on the color monitor 3 are identified in a second step for the print colors Fun of the supporting location network of the print color space. The second step divides into two sub-steps. In the first sub-step, the required color value triads m, gnu and by are measured for the print corner colors or for the color supporting or reference points of the print color space. In the second sub-step, the no-squired color value triads m, gnu and by are calculated for all print intermediate colors of the reference point network within the print color space.
For explanation, Figure 2 shows an idealized, cub-shaped print color space 33 within the YMC color coordinate system 34 comprising the eight print corner colors.
Specifically, these colors are the primary colors yellow (Y*), magenta lo*) and cyan (C*); the secondary colors red (YUMMY*), green (YOKE*), and blue (MCKEE); and black and white. At the same time, a supporting or reference point network I into which the print color space 33 is sub-divided is shown having three supporting or reference points 36 on every edge of the cube. Of course, the number of supporting or reference points is substantially higher in the practical illustrative embodiment. Each supporting or reference point n of a print color Fun is topically defined in the YMC color coordinate system 34 by a triad Yin, Men, and Oh of color separation values. One color value triad rung and by is allocated in accordance with equation I to every supporting or reference point n. The number of memory locations in the supporting or reference value memory 24 for the color value triads rn,bn,and gun to be allocated corresponds to the number ox reference points n in the print color space 33. The memory locations of the supporting or reference value memory 24 are addressable by the addresses 0 am, IBM and 0~cm. Every memory location n has a corresponding supporting or reference point lo n allocated to it in such fashion that the address triad an, by, and an with which the corresponding memory location n is addressable corresponds to the triad Y'n,M'n, and Con of color separation values for the corresponding supporting or refer-once location n. Thus, for example, the memory location alto-acted to the corner color "white" is addressable by the addresses 0,0, and 0 and the memory location allocated to the corner color "black," is addressable by the addresses am,bm, and cm.
In the practical embodiment, a "three-dimensional"
supporting or reference value memory is not employed for the deposit of three color values per memory location, but rather three memories separately addressable by the addresses anon and an in which respectively one color value of the allocated color value triads is deposited are employed.
For the execution of the first sub step eight color separation value triads are first formed and are successively forwarded to the color monitor 3 in order to successively generate eight monitor colors. The color separation value triads are then iteratively varied such that the monitor colors are chromatically matched to the print corner colors, whereby the eight matched monitor colors represent the eight monitor corner colors.
~:225~L49 In the illustrative embodiment described in Figure l, the color separation value triads are generated and modified with the assistance of the color regulators 31 in the color generator 18 and the color modifications are visually checked 5 on the color monitor 3. For matching of the monitor colors to the print corner colors, the color regulators 31 for "yellow", "magenta", and "cyan" are actuated, whereas the color regulator 31 for "black" is set constant such that the corrected color separation value K' becomes zero, whereby no lo signal superimposition in the superimposition stages 27 occurs during the matching operation.
By actuating the color regulators 31 fur the colors "yellow", "magenta", and "cyan", the respective luminance of the individual phosphors of the color monitor 3 complementary to the "colors" of the color regulators 31 are influenced, as proceeds from the following Table.
For the visual check of the color matching for example, real print corner colors are employed, i.e. colors that were printed with real inks on the impression paper under the conditions prevailing during the later impression printing. Such true print corner colors are available in the form of printed color fields which are also referred to as color scale, color atlas, or color chart.
The described relationships are compiled below in the form of a Table:
Corner Individual Phosphors Colors Color Regulators Influenced Yellow cyan and magenta red and go agent cyan and yellow red and blue Cyan yellow and magenta blue and green Red cyan red Green magenta green Blue yellow blue White cyan,magenta,yellow red, green, and blue Black cyan,magenta,yellow red, green, blue ~225~L~9 The monitor corner colors are, for example, repro-sensed as color fields which cover only a small part of the picture screen surface in terms of area The color value triads rn,gn,and by required for the isochromatic representation of the monitor corner colors are measured in the measuring stage 26, whereby every measuring operation between the individual representations is initiated by pressing a key 37. The measured color value triads rn,gn, and by are transferred via data busses 38 and the arithmetic stage 25 into the supporting or reference value memory 24 and are deposited there under the addresses anon and an alloy acted to the print corner colors Fun, as proceeds from the following Table:
;. :
Measured Color Addresses of Corner Value Triad of the Supporting color the Corner Colors Value Memory Yellow rye gyp r by I, cm, by Magenta rum gmi by am, O, cm Cyan no' go' be I' I' Cm Red or grow by am, by, O
Green rug, go, by am, O, cm Blue rub go by I by, cm site row' go' by I I
Black us' go' by am' by Cm For the visual comparison of monitor colors and print colors, a light box in the form of a light well is advantageously employed, this being placed on the picture screen with an opening. This opening has the size and shape of the picture screen surface, so that the picture screen is shielded from outside light. The opposite opening of the light box serves as a viewing aperture for the operator. The light box also comprises a partition between the openings ~25~9 and parallel thereto with a viewing aperture through which the operator observes the color field generated on the picture screen. The comparison color fields are applied to that side of the partition facing the viewing aperture, and are applied thereto in the region of the viewing aperture. The compare-son color fields are advantageously illuminated by a standardized light source whose brightness is matched to the rightness of the picture screen. For this purpose, the - standardized light source illuminates an art paper and the brightness of the standardized light source is set such that the light reflected from the art paper has the same bright-news as the picture screen.
Alternatively to the above-described visual color comparison, a measuring comparison of color identification values, for example of standardized color values, can also be undertaken for matching the monitor corner colors to the print corner colors. In this case, the standardized color _ values ED YE, and ED of the print corner colors are measured in a color chart or the like with the assistance of a color measuring means. The standardized color values EM, Ye, and EM of the monitor colors on the picture screen of the color monitor 3 are then likewise measured with a color measuring means and the color separation value triads are varied with the assistance of the manually actuatable color regulators 31 of the color generator 18 until the standardized color values EM, YE, and EM indicated at the color measuring means coin-aide with the previously identified standardized color values ED, YE, and ED of the print corner colors. The color value triads required therefore are measured and stored as described.
- 122514~
In a preferred embodiment of the circuit arrangement which it shown in Figure 3, the matching of the monitor corner colors to the print corner colors is automatically executed, so that the manual actuation of the color regular ions 31 and the purely visual color comparison or readings of a color measuring means are eliminated in an advantageous fashion.
The color values r, g, and b required for the repro-sensation of the monitor corner colors can also bye calculated from the standardized color values of the print corner colors ED, YE, and ED and the known standardized color values of the individual phosphors of the color monitor 3 for maximum picture white (XR,YR,ZR), (XG~YG, G) B B
according to equations (5), wherein a completed monitor linearization is assumed:
- EM - r I OR XG B
D = M = g . R G YE (5 D EM b LO G B
After the measuring operation, the calculation of the color value triads m, gnu and by occurs in accordance with the second sub-step for the intermediate colors dependent on that type of printing (rotogravure, offset) that is supposed to be simulated on the color monitor.
The identification of the color value triads m, gnu and by for the intermediate colors shall be explained with reference to the example for an offset printing simulation.
In this case, the color value triads are found by solving the known Neugebauer equations.
In auto type trichromatic printing, the eight corner colors of the print color space which are defined by stand-ardized color values X, Y, and Z, arise by side-by-side and ~225~
partial superimposed printing of raster points of the print-in inks yellow, magenta, and cyan. The primary colors yellow (Zeus), magenta (Xm,Ym,Zm), and Ryan (Xc,Yc,Zc~
arise by side-by-side printing of raster points of the print-in inks; the secondary colors red (Xr,Yr,Zr), green (Xg,Yg,Zg) and blue (Xb,Yb,Z~ arise by partial overlap of raster point of two printing inks; and black (Xs,Ys,Zs) arises by super-imposed printing of raster points of all three printing inks, with white tXW,YW,ZW) arising in case no raster points are printed.
According to Neugebauer, the standardized color values X, Y, and Z of an intermediate color arise according to equation I by addition of the standardized color values of the corner colors, whereby the standardized color values of the corner colors are effective in accordance with the probable or statistical area proportions 0 of the corner dolors:
OW WOW Y IY;I m 3 2 0 ED i ZOO ml l C
Or Xg l Xb us (6) or Ye + go L b Ye + I LUCY ¦.
The probable area proportions 0 of the eight corner colors are dependent in the following fashion on the respect live raster point sizes (~) or area coverage values, ire.
dependent on the color separation values M, and C of the resulting color . -18-~%~
ow = (1 - I M) Al Y) White) = Y (1 - M) (1 - Of (Yellow) m = M (1 - Y) C) (Magenta) I = C Y) If M) (Cowan (7) yipper = M Y C) Fred) = C Y M) (Green) b = C M Y) (Blue) us = Y C M killer black According to equations 56) and (7), thus the stank dardized color values XD,YD, and ED of the print intermediate colors can be calculated from the color separation values Y, M, and C ox the print intermediate colors and the measured standardized color values of the print corner colors.
On the other hand, the standardized color values XM,YM, and EM of the monitor intermediate colors can be de-fined according to equation (5) by the color values r, g, and as well as by the known standardized color values of the individual phosphors.
The color values m, gnu and by required for the -color coincidence between print intermediate colors and monk-ion intermediate colors (XD=XM; YE YE; ED M) fated from equation (5) in the arithmetic stage 25 and can be written over into the supporting value memory 24.
In case the standardized color values of the print corner colors are not present, they could be calculated in accordance with equation (I from the known standardized color values of the individual phosphors and the stored color values r, g, and b for the monitor corner colors. The standardized color values of the print intermediate colors can then be determined with the calculated standardized color values with equations (6) and (7).
~25~
After the supporting value memory 24 has been filled, a check of the memory filling preferably occurs since triads Y, M, and C of color separation values of intermediate colors of the print color space are input into the color converter 20 with the color generator 18. The allocated color value triads r, g, and b are then calculated in the interpolation stage 23 with the assistance of the supporting values deposited in the supporting value memory 24. Finally they are converted into video drive signals rev TV' and by. In order to simplify the check" for example, the triads Y, M, and C of color separation values for various characteristic intermediate colors of the print color space are stored in callable fashion in the color generator 18.
If it turns out in the check of the intermediate colors that one of the intermediate colors is to be modified, a partial correction of the memory filling is executed with the assistance of the arithmetic stage 25.
This partial correction advantageously occurs in accordance with the European wetters Patent 0004078, corresponding to US. Patent 4,328,515. For this purpose, the color value triads of the intermediate color to be maximally corrected are first modified in the desired sense and, subsequently, all color value triads within a three-dimensional correction region around the intermediate color to be maximally corrected are reconnected in such fashion that a gradual correction progression between the modified color value triads of the corresponding intermediate color and the color value triads at the edge of the correction region is achieved Figure 3 shows a preferred improvement of the Syria cult arrangement shown in Figure 1 comprising a device for 5~g automatic matching of the monitor colors generated at the color monitor 3 to the corner colors of the print color space, lo referred to as print corner colors. This additional device is composed of a color measuring means 40, of a rated value memory 41, of a control stage 42, and of a color generator 18* that has been modified in comparison to Figure 1.
The color measuring device Ed, for example model TO 1 of the Thomas Kiwi is directed to the picture screen I of the color monitor such that it acquires the eight monitor colors successively represented as color fields on the picture screen during the adjustment operation and defines their standardized color value triads XM,YM, and EM as actual value triads of the monitor colors. The standardized color value triads XM,YM, and EM of the monitor colors are con-tenuously serially forwarded via a data bus 43 to the control stage 42 and are stored there.
Serving as rated value triads for the automatic matching are, for example, the standardized color value in-ads XD,YD, and ED of the print corner colors measured in color chart or values derived therefrom. The eight print corner colors are written via a data input 44 into the rated value memory 41 and are called in as needed by the control stage 42 via a data bus 45 with the assistance of a read 2, clock on a line 46.
Dependent on the rated value/actual value comparison, the control stage 42 generates three variable color signal values for "yellow", "magenta", and "cyan" as well as a ; constant color signal value for "black" which was already explained in Figure 1. Which individual phosphors of the color monitor 3 are to be varied in luminance as well as the ~L2;25~
amount and direction of the luminance modification are de-fined by the color signal values for "yellow", "magenta", and "cyan". The Table compiled on page 15 thus applies by analogy. The color signal values are supplied via data busses 47 to the modified color generator 18*. Instead of the color regulators 31, the modified color generator 18*
contains four memory registers 48 into which the color signal values coming from the control stage 42 are written via data inputs 49 with the assistance of a write clock on a line 50 generated in the control stage. The data outputs of the memory registers 48 are connectable via the data busses 52 and the switches 30 to the gradation stages Lydia and, thus to the color monitor 3 as well. As already described for the manual adjustment with the assistance of the color regular ions, the matching of a monitor color to a print corner colons iteratively executed in successive cycles. Accordingly, one cycle comprises a color measurement, a rated value/actual value comparison, and alteration of the color signal values on the basis of the comparison. The following cycle again begins with a color measurement. The cycles are executed until coincidence between rated value triad and actual value triad for a monitor color, or an allowed slight deviation is identified. The control stage 42 then forwards a measure instruction via a fine 53 to the measuring stage 25 which then measures the color value triad r, g, and b required for the representation of the matched monitor color The match-in operation for a new monitor color then begins, for which purpose the control stage 42 calls in the corresponding, new rated value triad from the rated value memory 41. The automatic sequencing operation is concluded when all eight monitor corner colors have been matched to the print corner so colors. This can, or example, be indicated to the operator. Of course, the operator can arbitrarily interrupt the operation or repeat it for a specific monitor color.
Various circuits previously described will now be discussed in greater detail.
In Figure 1, full frame memory 5 for storing color separation values of a color picture image repetition memory 7 for generating a still picture on a monitor, and address controller 8 are known from U. S. Patent 4,3~3,399. The full frame memory is referenced "1" therein, the image repetition memory "7", and the address controller "Al'. The address controller "8" is also shown in detail in Figure 11 of U. S. Patent ~,393,399.
The correction stage 6 of the present application can be constructed in accordance with U. S. Patent 3,885,244 or in accordance with US. Patent 4,285,009 (Figure 3).
The color generator I is composed, for example, of a voltage source, traditional potentiometers (color regulators 31), and analog-to~digital converters. Variable sub voltages which are converted into data in the analog-to-digital converter, and are output via the busses 14, are generated with the assistance of the potentiometers as voltage dividers. The gradation stages lga-19d and the linearization stages 21 are, for example, programmable read-only memories (PROM) which are loaded with the data calculated according to a gradation curve or a linearization curve. This is a standard technique which, for example, is known from U. S. Patent 4,075,662 for film linearization, i.e. for the compensation of the non-linearities ox a film. This known technique is applied in analogous fashion I
in the present application for the compensation of non-linearities of a color monitor. As previously mentioned, the color converter 20 can be an allocator memory which is addressed by the values Y', M', and C' and which outputs not the values Y', M', and C', but the values 4, g, and b that were previously allocated to them.
In the illustrative embodiment shown, the allocator memory is replaced by a smaller supporting value memory 24 and by an interpolator stage 23. This is standard technology for saving memory space. This technology is known, for example, from US. Patent 4,075,662 (Figure 3) in which the combination of supporting value memory "160" and interpolator stage "161" is disclosed.
The arithmetic unit 25 is, for example, a microprocessor which only has the task of depositing the data measured in the measuring unit 26 under the right addresses of the supporting value memory 24. The addressing of the supporting value memory has been previously described. The measuring unit 26 is a traditional digital measuring unit.
Although various minor changes and modifications might be proposed by those skilled in the art, it will be understood that we wish to include within the claims of the patent warranted heron all such changes and modifications as reasonably come within our contribution to the art.
On The Drawings-Figure l is a schematic circuit arrangement for a color viewing apparatus;
Figure 2 is a graphic illustration of a printing color space; and Figure 3 is an advantageous development of a circuit arrangement of the invention.
Figure 1 shows an illustrative embodiment of a air-cult arrangement for simulating a multi-color reproduction on a color monitor for a color evaluation and color correction of an anticipated multi-color reproduction before a printing process. This is referred to below as a color viewing apparatus.
The color viewing apparatus is essentially composed of a signal source 1, of a transformation circuit 2, of a color monitor 3, and of a clock generator 4.
The signal source 1 generates digital color swooper-lion values Ye M, C, and K for the color separations "yellow"
(Y), "magenta" (M), "cyan" (C) and "black" lo) of a color picture to be printed. The digital color separation values Y, M, C, and K are a measure for the required metered amounts of printing inks or for the size of the raster points, in percent. The digital color separation values have, for example, a word length of 8 bits, whereby "black" (100% raster point size) is allocated to the digital color separation value 0 and "white" (0% raster point size) is allocated to the digital color separation value 225. A total of 254 gray scale values are discriminated between "black" and "white".
The signal course 1 can contain an electronic color camera which generates measured color value signals I G, and I
B by a video-wise, point-by-point and line byline scanning of the color picture to be printed or to be represented on the color monitor 3.
An adjustable color correction stage following the color camera converts the measured color value signals R, G, and B into the color separation signals Y, M, C, and K
according to the laws of subtractive color mixing.
In the illustrative embodiment shown, the signal source 1 is composed of a full frame memory S, ox a correction stage 6, of an image repetition memory 7, and of an address controller 8. The digital color separation values Y, M, C, and K of a discrete image or of an already assembled printing page are deposited in the full frame memory 7. The color separation values Y, M, C, and K of a discrete image were generated, for example, in a color scanner. The combination of the color separation values of various discrete images to form the color separation values Jo of a printing page occurs according to a lay-out plan, for example by an electronic page make-up in an image processing system of the German OX 21 61 038, corresponding to US.
Patent 1,407,487. The color separation values required for the representation of the color picture or of a trimmed picture on the color monitor 3 from, for example, 512 x 512 picture elements, are selected or calculated from the entire detest of the full frame memory 5, and are loaded from there via the data busses 9 into the image repetition memory 7 which comprises a storage capacity for 512 x 512 color separation values corresponding to the number of picture elements. For the transmission of the color separation values, the address controller 8 calls the corresponding addresses in the full frame memory 5 and in the Ed SLY
image repetition memory 7 via the address busses 10 and 11l and generates the corresponding read clocks on control busses 12 and 13.
For the representation of the color picture on the color monitor 3, the address controller 8 cyclically calls in the addresses of the image repetition memory 7 via the address bus 10. The addressed color separation values Y, M, C, and K are read out line-by-line and picture-element-by-picture-element within every line with the assistance of the read clock ox the control bus 12, and are supplied via the data busses 14 to the transformation circuit 2. In the transformation circuit 2, the color separation values Y, M, C, and K are transformed into video drive signals rev go and by for the color monitor 3 on lines 15 such that the color picture displayed on the color monitor 3 conveys the.
same chromatic impression as the color picture printed on the impression paper under production run conditions.
The point-by-point and line-by-line recording of the color picture on the color monitor 3 occurs, for example, according to the line interlace method with 50 fields/sec in order to produce a flicker-free image. Based on the technique standard in television, the clock generator 4 generates the horizontal and vertical deflection signals as well as the line start pulses and picture start pulses on lines 16. The address controller 8 in the signal source 1 supplies cores-pounding horizontal and vertical sync pulses via lines 17 to the clock generator 4, so that the monitor recording is synchronized with the read operation of the color separation values from the image repetition memory 7.
The operator can now evaluate the displayed color picture and, when necessary, undertake color corrections by '~3"Z~
changing the color separation values Y, M, C, an K with the assistance of the correction stage 6 in the full frame memory : SO The color separation values Y, M, C, and K modified in the full frame memory 5 are automatically transferred into the image repetition memory 7, so that the color-corrected picture respectively appears on the color monitor 3.
Each of the color separation values quadruplets Y, M, C, and K supplied by the signal source 1 represents a color printed on the impression paper, referred to below as print color, which arises by superimposed printing of different proportions of the yellow, magenta, cyan, and black colors, and by subtractive color mixing. Each print .. . .. . .
; color can be identified by a triad of standardized color values XDr YE, and ED The video drive values rev- go and by are a measure for the luminance of the individual phosphors "red", "green" and "blue" of the color monitor 3.
Each triad of video drive values rev go and by therefore represents a color formed on the color monitor 3 by additive color mixing of the components red, green, and blue, said color being referred to below as a monitor color. Every monitor color can likewise be identified by a triad of -standardized color values EM, YE, and EM-- The transformation stage 2 is composed of a color generator 18, of gradation stages Audi, of a color con-: 25 venter 20, of linearization stages 21, and of digital-to-analog converters 22. The color converter in turn comprises an interpolation stage 23, a supporting value memory 24, an arithmetic stage 25, a measuring stage 26, as well as super-imposition stages 27.
In the gradation stages lea lid, the color swooper-lion values Y, M, C, and K are corrected into color 12~ Lo separation values Y', M', I and K' according to equation I first according to gradation curves if:
Y',M',C'~X' = f~(Y,MrC,R). (1) The print gradation curves if, also referred to as print characteristics, take the parameters of the printing process, the impression paper, as well as the true inks into consideration. The gradation stages Lydia are designed, for example, as laudably memories (Russ in which the print gradation curves if are stored.
The corrected color separation value Y', My, C', and K' are forwarded to the color converter 20. In the color converter 20, the triad of color values or', g', b') which is required for the representation of the isochromatic monitor color is generated for every quadruplet of corrected color separation values (Y',M',C',K') of a print color:
go Jo foe MUCK (2) In the color converter 20, only the color separation values Y', M', C' corrected in the gradation stages Lydia are forwarded via the data busses 28 to the input of the interpolation stage 23, whereas the color separation values K' corrected in the gradation stage lea for the black separation proceed via a data bus 29 directly to the super-imposition stages Z7. In accordance with equation (3), the interpolation stage 23 first outputs an allocated triad of color values r, g, and b required for isochromatic represent station for every triad of corrected color separation values YUMMY', and C', ire. without taking the black separation into consideration:
rub = f3(Y',M',C;). (3) I
In the illustrative embodiment shown tile allocation accord-in to equation (3) is advantageously calculated only for a supporting point network of the print color space deposited in the supporting value memory 24, whereas all allocations required for recording the color picture on the color monitor 3 are identified by continuous inter-pollution in the interpolation stage 23. Alternatively, the allocations can also be calculated before the recording of the color picture, and are calculated for all theoretically possible colors of the print color space. In this case, the interpolation stage 23 is replaced by a eon-despondingly larger allocator memory.
The color values r, g, and b output from the interpolation stage 23 arc joined in multiplicative fashion in the superimposition stages 27 to the color separation values K' for the black separ.ltioll in order to obtain the corrected color values r', g', and b' at the out-put of the color converter 20.
rub = f4(r,g,b) (4) The corrected color values r', g', and b' represent the monitor colors to be generated on the color monitor 3, but which are not achieved due to the monitor characteristics, i.e. due to the non-linear relation-ships between the radiation density values of the individual phosphors and the video drive values. For this reason, linear relationships must be produced by a so-called monitor linearization between the radiation density value of the red phosphor and the video drive values r', the radiation density value of the green phosphor, and the video drive values g', as well as between the radiation density value of the blue phosphor and the video drive values b'.
~L~25~ 9 This monitor linearization occurs since the color values r', g', and b' are converted into corresponding video drive values I go by in the linearization stages 21 based on the measure of the monitor characteristics. The linear-ration stages 21 are designed, for example, as laudably memories (Rams) in which the calculated video drive values I go by are digitally stored. The stored digital video drive values rev go by are converted into the analog video drive values rev, go and by on the lines 15 in the digital-to analog converters 22 which follow the linearization stages 21.
The monitor characteristics can be identified by a measurement of the radiation density at the color monitor as a function of the drive values. However, the monitor characteristics specified by the manufacturer of the color monitor can also be employed. In case the specified monitor characteristics are not exact enough, a correspondingly larger number of characteristic values could be identified by interpolation.
It is within the scope of the invention to already execute the calculation of the corrected color separation values Y', M', C', and K' in the gradation stages Lydia, the multiplicative combination of the color values r, g, and b with the corrected color separation values Al of the black separation and/or the linearization of the video drive values TV go and by before the representation of the color picture on the color monitor 3, and to take the corresponding cowlick-lotions into consideration in the detest of the supporting value memory 24 or of the allocator memory.
The function of the color viewing apparatus having been explained, the method for the identification of the ~L2;~5~4~3 color values r, g, and b required for a chromatically equip valet color picture representation dependent on the color separation values Yo-yo M', and C' for the supporting location network or for the supporting value memory 24 in the color converter 20 before actual operation of the color viewing apparatus shall be discussed. In this phase of operations, a changeover 30 is situated in the illustrated position, so that the color generator 18 is connected to the gradation stages Audi.
It is thus assumed that the gradation stages Lydia and the supporting value memory 24 function linearly at first, since the gradation stages Lydia as well as the supporting value memory 24 are loaded with linear functions In a first step, a calibration of the color monitor 3 to the brightest white (maximum picture white) and to the ; darkest black (maximum picture depth) is undertaken. It is guaranteed as a result of the white calibration that the color monitor 3 is illuminated with the brightest white when all color separation values Y=M=C=K=255 (rated white;
0% raster point size) or when the video drive values rev, go and by supplied to the color converter 20 are at maximum. For white calibration, the required color swooper-lion values are set in the color generator 18 with the assistance of the color regulators 31 "yellow", "magenta", "cyan", and "black", the monitor white thus generated being visually compared to a model original "picture white", for example to an art paper, and the operating parameters of the color monitor 3 being varied until the monitor white corresponds to the maximum picture white.
A following black calibration is intended to insure that the color monitor 3 generates the blackest black when ~:2~4g the color separation values Y=M=C=K=0 (picture black; lQ0~
roster point size) so when the video drive values rev glove and ho are at a minimum. The black matching occurs analog guzzle with a corresponding model original "black.
After the described calibration, those color value triads m, gnu and by which are required for isochromatic reproduction of the print colors Fun or of the multi-color reproduction on the color monitor 3 are identified in a second step for the print colors Fun of the supporting location network of the print color space. The second step divides into two sub-steps. In the first sub-step, the required color value triads m, gnu and by are measured for the print corner colors or for the color supporting or reference points of the print color space. In the second sub-step, the no-squired color value triads m, gnu and by are calculated for all print intermediate colors of the reference point network within the print color space.
For explanation, Figure 2 shows an idealized, cub-shaped print color space 33 within the YMC color coordinate system 34 comprising the eight print corner colors.
Specifically, these colors are the primary colors yellow (Y*), magenta lo*) and cyan (C*); the secondary colors red (YUMMY*), green (YOKE*), and blue (MCKEE); and black and white. At the same time, a supporting or reference point network I into which the print color space 33 is sub-divided is shown having three supporting or reference points 36 on every edge of the cube. Of course, the number of supporting or reference points is substantially higher in the practical illustrative embodiment. Each supporting or reference point n of a print color Fun is topically defined in the YMC color coordinate system 34 by a triad Yin, Men, and Oh of color separation values. One color value triad rung and by is allocated in accordance with equation I to every supporting or reference point n. The number of memory locations in the supporting or reference value memory 24 for the color value triads rn,bn,and gun to be allocated corresponds to the number ox reference points n in the print color space 33. The memory locations of the supporting or reference value memory 24 are addressable by the addresses 0 am, IBM and 0~cm. Every memory location n has a corresponding supporting or reference point lo n allocated to it in such fashion that the address triad an, by, and an with which the corresponding memory location n is addressable corresponds to the triad Y'n,M'n, and Con of color separation values for the corresponding supporting or refer-once location n. Thus, for example, the memory location alto-acted to the corner color "white" is addressable by the addresses 0,0, and 0 and the memory location allocated to the corner color "black," is addressable by the addresses am,bm, and cm.
In the practical embodiment, a "three-dimensional"
supporting or reference value memory is not employed for the deposit of three color values per memory location, but rather three memories separately addressable by the addresses anon and an in which respectively one color value of the allocated color value triads is deposited are employed.
For the execution of the first sub step eight color separation value triads are first formed and are successively forwarded to the color monitor 3 in order to successively generate eight monitor colors. The color separation value triads are then iteratively varied such that the monitor colors are chromatically matched to the print corner colors, whereby the eight matched monitor colors represent the eight monitor corner colors.
~:225~L49 In the illustrative embodiment described in Figure l, the color separation value triads are generated and modified with the assistance of the color regulators 31 in the color generator 18 and the color modifications are visually checked 5 on the color monitor 3. For matching of the monitor colors to the print corner colors, the color regulators 31 for "yellow", "magenta", and "cyan" are actuated, whereas the color regulator 31 for "black" is set constant such that the corrected color separation value K' becomes zero, whereby no lo signal superimposition in the superimposition stages 27 occurs during the matching operation.
By actuating the color regulators 31 fur the colors "yellow", "magenta", and "cyan", the respective luminance of the individual phosphors of the color monitor 3 complementary to the "colors" of the color regulators 31 are influenced, as proceeds from the following Table.
For the visual check of the color matching for example, real print corner colors are employed, i.e. colors that were printed with real inks on the impression paper under the conditions prevailing during the later impression printing. Such true print corner colors are available in the form of printed color fields which are also referred to as color scale, color atlas, or color chart.
The described relationships are compiled below in the form of a Table:
Corner Individual Phosphors Colors Color Regulators Influenced Yellow cyan and magenta red and go agent cyan and yellow red and blue Cyan yellow and magenta blue and green Red cyan red Green magenta green Blue yellow blue White cyan,magenta,yellow red, green, and blue Black cyan,magenta,yellow red, green, blue ~225~L~9 The monitor corner colors are, for example, repro-sensed as color fields which cover only a small part of the picture screen surface in terms of area The color value triads rn,gn,and by required for the isochromatic representation of the monitor corner colors are measured in the measuring stage 26, whereby every measuring operation between the individual representations is initiated by pressing a key 37. The measured color value triads rn,gn, and by are transferred via data busses 38 and the arithmetic stage 25 into the supporting or reference value memory 24 and are deposited there under the addresses anon and an alloy acted to the print corner colors Fun, as proceeds from the following Table:
;. :
Measured Color Addresses of Corner Value Triad of the Supporting color the Corner Colors Value Memory Yellow rye gyp r by I, cm, by Magenta rum gmi by am, O, cm Cyan no' go' be I' I' Cm Red or grow by am, by, O
Green rug, go, by am, O, cm Blue rub go by I by, cm site row' go' by I I
Black us' go' by am' by Cm For the visual comparison of monitor colors and print colors, a light box in the form of a light well is advantageously employed, this being placed on the picture screen with an opening. This opening has the size and shape of the picture screen surface, so that the picture screen is shielded from outside light. The opposite opening of the light box serves as a viewing aperture for the operator. The light box also comprises a partition between the openings ~25~9 and parallel thereto with a viewing aperture through which the operator observes the color field generated on the picture screen. The comparison color fields are applied to that side of the partition facing the viewing aperture, and are applied thereto in the region of the viewing aperture. The compare-son color fields are advantageously illuminated by a standardized light source whose brightness is matched to the rightness of the picture screen. For this purpose, the - standardized light source illuminates an art paper and the brightness of the standardized light source is set such that the light reflected from the art paper has the same bright-news as the picture screen.
Alternatively to the above-described visual color comparison, a measuring comparison of color identification values, for example of standardized color values, can also be undertaken for matching the monitor corner colors to the print corner colors. In this case, the standardized color _ values ED YE, and ED of the print corner colors are measured in a color chart or the like with the assistance of a color measuring means. The standardized color values EM, Ye, and EM of the monitor colors on the picture screen of the color monitor 3 are then likewise measured with a color measuring means and the color separation value triads are varied with the assistance of the manually actuatable color regulators 31 of the color generator 18 until the standardized color values EM, YE, and EM indicated at the color measuring means coin-aide with the previously identified standardized color values ED, YE, and ED of the print corner colors. The color value triads required therefore are measured and stored as described.
- 122514~
In a preferred embodiment of the circuit arrangement which it shown in Figure 3, the matching of the monitor corner colors to the print corner colors is automatically executed, so that the manual actuation of the color regular ions 31 and the purely visual color comparison or readings of a color measuring means are eliminated in an advantageous fashion.
The color values r, g, and b required for the repro-sensation of the monitor corner colors can also bye calculated from the standardized color values of the print corner colors ED, YE, and ED and the known standardized color values of the individual phosphors of the color monitor 3 for maximum picture white (XR,YR,ZR), (XG~YG, G) B B
according to equations (5), wherein a completed monitor linearization is assumed:
- EM - r I OR XG B
D = M = g . R G YE (5 D EM b LO G B
After the measuring operation, the calculation of the color value triads m, gnu and by occurs in accordance with the second sub-step for the intermediate colors dependent on that type of printing (rotogravure, offset) that is supposed to be simulated on the color monitor.
The identification of the color value triads m, gnu and by for the intermediate colors shall be explained with reference to the example for an offset printing simulation.
In this case, the color value triads are found by solving the known Neugebauer equations.
In auto type trichromatic printing, the eight corner colors of the print color space which are defined by stand-ardized color values X, Y, and Z, arise by side-by-side and ~225~
partial superimposed printing of raster points of the print-in inks yellow, magenta, and cyan. The primary colors yellow (Zeus), magenta (Xm,Ym,Zm), and Ryan (Xc,Yc,Zc~
arise by side-by-side printing of raster points of the print-in inks; the secondary colors red (Xr,Yr,Zr), green (Xg,Yg,Zg) and blue (Xb,Yb,Z~ arise by partial overlap of raster point of two printing inks; and black (Xs,Ys,Zs) arises by super-imposed printing of raster points of all three printing inks, with white tXW,YW,ZW) arising in case no raster points are printed.
According to Neugebauer, the standardized color values X, Y, and Z of an intermediate color arise according to equation I by addition of the standardized color values of the corner colors, whereby the standardized color values of the corner colors are effective in accordance with the probable or statistical area proportions 0 of the corner dolors:
OW WOW Y IY;I m 3 2 0 ED i ZOO ml l C
Or Xg l Xb us (6) or Ye + go L b Ye + I LUCY ¦.
The probable area proportions 0 of the eight corner colors are dependent in the following fashion on the respect live raster point sizes (~) or area coverage values, ire.
dependent on the color separation values M, and C of the resulting color . -18-~%~
ow = (1 - I M) Al Y) White) = Y (1 - M) (1 - Of (Yellow) m = M (1 - Y) C) (Magenta) I = C Y) If M) (Cowan (7) yipper = M Y C) Fred) = C Y M) (Green) b = C M Y) (Blue) us = Y C M killer black According to equations 56) and (7), thus the stank dardized color values XD,YD, and ED of the print intermediate colors can be calculated from the color separation values Y, M, and C ox the print intermediate colors and the measured standardized color values of the print corner colors.
On the other hand, the standardized color values XM,YM, and EM of the monitor intermediate colors can be de-fined according to equation (5) by the color values r, g, and as well as by the known standardized color values of the individual phosphors.
The color values m, gnu and by required for the -color coincidence between print intermediate colors and monk-ion intermediate colors (XD=XM; YE YE; ED M) fated from equation (5) in the arithmetic stage 25 and can be written over into the supporting value memory 24.
In case the standardized color values of the print corner colors are not present, they could be calculated in accordance with equation (I from the known standardized color values of the individual phosphors and the stored color values r, g, and b for the monitor corner colors. The standardized color values of the print intermediate colors can then be determined with the calculated standardized color values with equations (6) and (7).
~25~
After the supporting value memory 24 has been filled, a check of the memory filling preferably occurs since triads Y, M, and C of color separation values of intermediate colors of the print color space are input into the color converter 20 with the color generator 18. The allocated color value triads r, g, and b are then calculated in the interpolation stage 23 with the assistance of the supporting values deposited in the supporting value memory 24. Finally they are converted into video drive signals rev TV' and by. In order to simplify the check" for example, the triads Y, M, and C of color separation values for various characteristic intermediate colors of the print color space are stored in callable fashion in the color generator 18.
If it turns out in the check of the intermediate colors that one of the intermediate colors is to be modified, a partial correction of the memory filling is executed with the assistance of the arithmetic stage 25.
This partial correction advantageously occurs in accordance with the European wetters Patent 0004078, corresponding to US. Patent 4,328,515. For this purpose, the color value triads of the intermediate color to be maximally corrected are first modified in the desired sense and, subsequently, all color value triads within a three-dimensional correction region around the intermediate color to be maximally corrected are reconnected in such fashion that a gradual correction progression between the modified color value triads of the corresponding intermediate color and the color value triads at the edge of the correction region is achieved Figure 3 shows a preferred improvement of the Syria cult arrangement shown in Figure 1 comprising a device for 5~g automatic matching of the monitor colors generated at the color monitor 3 to the corner colors of the print color space, lo referred to as print corner colors. This additional device is composed of a color measuring means 40, of a rated value memory 41, of a control stage 42, and of a color generator 18* that has been modified in comparison to Figure 1.
The color measuring device Ed, for example model TO 1 of the Thomas Kiwi is directed to the picture screen I of the color monitor such that it acquires the eight monitor colors successively represented as color fields on the picture screen during the adjustment operation and defines their standardized color value triads XM,YM, and EM as actual value triads of the monitor colors. The standardized color value triads XM,YM, and EM of the monitor colors are con-tenuously serially forwarded via a data bus 43 to the control stage 42 and are stored there.
Serving as rated value triads for the automatic matching are, for example, the standardized color value in-ads XD,YD, and ED of the print corner colors measured in color chart or values derived therefrom. The eight print corner colors are written via a data input 44 into the rated value memory 41 and are called in as needed by the control stage 42 via a data bus 45 with the assistance of a read 2, clock on a line 46.
Dependent on the rated value/actual value comparison, the control stage 42 generates three variable color signal values for "yellow", "magenta", and "cyan" as well as a ; constant color signal value for "black" which was already explained in Figure 1. Which individual phosphors of the color monitor 3 are to be varied in luminance as well as the ~L2;25~
amount and direction of the luminance modification are de-fined by the color signal values for "yellow", "magenta", and "cyan". The Table compiled on page 15 thus applies by analogy. The color signal values are supplied via data busses 47 to the modified color generator 18*. Instead of the color regulators 31, the modified color generator 18*
contains four memory registers 48 into which the color signal values coming from the control stage 42 are written via data inputs 49 with the assistance of a write clock on a line 50 generated in the control stage. The data outputs of the memory registers 48 are connectable via the data busses 52 and the switches 30 to the gradation stages Lydia and, thus to the color monitor 3 as well. As already described for the manual adjustment with the assistance of the color regular ions, the matching of a monitor color to a print corner colons iteratively executed in successive cycles. Accordingly, one cycle comprises a color measurement, a rated value/actual value comparison, and alteration of the color signal values on the basis of the comparison. The following cycle again begins with a color measurement. The cycles are executed until coincidence between rated value triad and actual value triad for a monitor color, or an allowed slight deviation is identified. The control stage 42 then forwards a measure instruction via a fine 53 to the measuring stage 25 which then measures the color value triad r, g, and b required for the representation of the matched monitor color The match-in operation for a new monitor color then begins, for which purpose the control stage 42 calls in the corresponding, new rated value triad from the rated value memory 41. The automatic sequencing operation is concluded when all eight monitor corner colors have been matched to the print corner so colors. This can, or example, be indicated to the operator. Of course, the operator can arbitrarily interrupt the operation or repeat it for a specific monitor color.
Various circuits previously described will now be discussed in greater detail.
In Figure 1, full frame memory 5 for storing color separation values of a color picture image repetition memory 7 for generating a still picture on a monitor, and address controller 8 are known from U. S. Patent 4,3~3,399. The full frame memory is referenced "1" therein, the image repetition memory "7", and the address controller "Al'. The address controller "8" is also shown in detail in Figure 11 of U. S. Patent ~,393,399.
The correction stage 6 of the present application can be constructed in accordance with U. S. Patent 3,885,244 or in accordance with US. Patent 4,285,009 (Figure 3).
The color generator I is composed, for example, of a voltage source, traditional potentiometers (color regulators 31), and analog-to~digital converters. Variable sub voltages which are converted into data in the analog-to-digital converter, and are output via the busses 14, are generated with the assistance of the potentiometers as voltage dividers. The gradation stages lga-19d and the linearization stages 21 are, for example, programmable read-only memories (PROM) which are loaded with the data calculated according to a gradation curve or a linearization curve. This is a standard technique which, for example, is known from U. S. Patent 4,075,662 for film linearization, i.e. for the compensation of the non-linearities ox a film. This known technique is applied in analogous fashion I
in the present application for the compensation of non-linearities of a color monitor. As previously mentioned, the color converter 20 can be an allocator memory which is addressed by the values Y', M', and C' and which outputs not the values Y', M', and C', but the values 4, g, and b that were previously allocated to them.
In the illustrative embodiment shown, the allocator memory is replaced by a smaller supporting value memory 24 and by an interpolator stage 23. This is standard technology for saving memory space. This technology is known, for example, from US. Patent 4,075,662 (Figure 3) in which the combination of supporting value memory "160" and interpolator stage "161" is disclosed.
The arithmetic unit 25 is, for example, a microprocessor which only has the task of depositing the data measured in the measuring unit 26 under the right addresses of the supporting value memory 24. The addressing of the supporting value memory has been previously described. The measuring unit 26 is a traditional digital measuring unit.
Although various minor changes and modifications might be proposed by those skilled in the art, it will be understood that we wish to include within the claims of the patent warranted heron all such changes and modifications as reasonably come within our contribution to the art.
Claims (17)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method for isochromatic simulation of a multi-colored reproduc-tion on a color monitor wherein color separation values of a multi-colored reproduction to be represented are converted into video drive values for the color monitor which are required for the isochromatic simulation, comprising the steps of:
a) before simulation of the multi-colored reproduction i) prescribing color signal values, generating colors corres-ponding to the prescribed color signal values on the color monitor, and matching the generated monitor colors to corner colors of a print color space by changing the color signal values, whereby the print corner colors have been printed under conditions of the multi-color reproduction;
ii) identifying the color value triads, r,g,b required for the chromatically coinciding generation of the corner colors on the color monitor given consideration of a non-linear relationship between radiation density values of individual phosphors of the color monitor and the color values;
iii) for every corner color, allocating the identified color value triad r,g,b to a corresponding triad Y*,M*,C* of color separation values of three chromatic color separations of the corner color;
iv) respectively calculating color value triads r,g,b for intermediate colors of the print color space lying between the corner colors required for chromatically coinciding generation of the intermediate colors on the color monitor from triads Y,M,C of the three chromatic color separations given consideration of the reproduction process for the multi-colored reproduction; and v) for every intermediate color, allocating the calculated color value triad r,g,b to the corresponding triad Y,M,C of color separation values of the three chromatic color separations of the intermediate color;
and b) during simulation of the multi-colored reproduction i) calling in and modifying color separation values Y, M, C, K of the three chromatic color separations and of a black separation of the multi-colored reproduction into color separation values Y', M', C', K' according to a reproduction gradation curve employed in the later to occur multi-color reproduction;
ii) outputting the previously allocated color value triads r,g,b instead of color separation value triads Y',M',C' of the three chromatic color separations of the multi-colored reproduction;
iii) combining the output color value triads r, g, b with the modified color separation values K' of the black separation to form correc-ted color value triads r', g', b'; and iv) converting the corrected color value triads r', g', b' into video drive values r'v, g'v, b'v for the color monitor.
a) before simulation of the multi-colored reproduction i) prescribing color signal values, generating colors corres-ponding to the prescribed color signal values on the color monitor, and matching the generated monitor colors to corner colors of a print color space by changing the color signal values, whereby the print corner colors have been printed under conditions of the multi-color reproduction;
ii) identifying the color value triads, r,g,b required for the chromatically coinciding generation of the corner colors on the color monitor given consideration of a non-linear relationship between radiation density values of individual phosphors of the color monitor and the color values;
iii) for every corner color, allocating the identified color value triad r,g,b to a corresponding triad Y*,M*,C* of color separation values of three chromatic color separations of the corner color;
iv) respectively calculating color value triads r,g,b for intermediate colors of the print color space lying between the corner colors required for chromatically coinciding generation of the intermediate colors on the color monitor from triads Y,M,C of the three chromatic color separations given consideration of the reproduction process for the multi-colored reproduction; and v) for every intermediate color, allocating the calculated color value triad r,g,b to the corresponding triad Y,M,C of color separation values of the three chromatic color separations of the intermediate color;
and b) during simulation of the multi-colored reproduction i) calling in and modifying color separation values Y, M, C, K of the three chromatic color separations and of a black separation of the multi-colored reproduction into color separation values Y', M', C', K' according to a reproduction gradation curve employed in the later to occur multi-color reproduction;
ii) outputting the previously allocated color value triads r,g,b instead of color separation value triads Y',M',C' of the three chromatic color separations of the multi-colored reproduction;
iii) combining the output color value triads r, g, b with the modified color separation values K' of the black separation to form correc-ted color value triads r', g', b'; and iv) converting the corrected color value triads r', g', b' into video drive values r'v, g'v, b'v for the color monitor.
2. A method according to claim 1 wherein the non-linear relationship between radiation density values and color values is taken into considera-tion in the allocation of color value triads r, g, b and triads Y, M, C of color separation values.
3. A method according to claim 1 wherein the non-linear relationship between radiation density values and color values is taken into considera-tion in the conversion of the corrected color value triads r', g', b' into the video drive values r'v, g'v, b'v.
4. A method according to claim 1 wherein for simulating a multi-colored reproduction produced in offset printing, a) calculating the standardized color values ?, ?, ? of the intermediate colors of the multi-colored reproduction according to the Neugebauer equations by addition of fractions of the standardized color values of the eight print corner colors, whereby the fractions correspond to the probable area proportions of the corner colors which depend on one of the raster point sizes or color separation values Y, M, C of the printed intermediate colors; and b) determining the color value triads required for the chromati-cally coinciding generation of the intermediate colors on the color monitor from the standardized color values of the intermediate colors and the standardized color values of the individual phosphors of the color monitor.
5. A method according to claim 1 including the step of combining in multiplicative fashion the color value triads r, g, b with the color separation values K' of the black separation.
6. A method according to claim 1 including the step of undertaking the allocation of triads Y, M, C of color separation values and color value triads r, g, b for all theoretically possible colors of the print color space before the simulation of the multi-colored reproduction.
7. A method according to claim 1 including the steps of a) undertaking the allocation of triads Y, M, C of color separa-tion values and color value triads r, g, b before the simulation of the multi-colored reproduction only for a supporting point network of theore-tically possible colors of the print color space; and b) acquiring color value triads r, g, b corresponding to called color separation values Y, M, C, K of the multi-colored reproduction by interpolation during the simulation of the multi-colored reproduction, and outputting them.
8. A method according to claim 1 including the step of checking the matching of the monitor colors to the print corner colors by a visual com-parison of the colors.
9. A method according to claim 1 including the step of checking the matching of the monitor colors to the print corner colors by comparison of the measured acquired color identification values of the colors.
10. A method according to claim 1 wherein matching of the monitor colors to the print corner colors is automatically provided by a) employing the color identification values of one of the print corner colors or values derived therefrom as rated values for the monitor colors;
b) continuously measuring the color identification values of the monitor colors generated at the color monitor and employing them as actual values; and c) deriving the color signal values required for the matching of the colors from a comparison of rated values and actual values.
b) continuously measuring the color identification values of the monitor colors generated at the color monitor and employing them as actual values; and c) deriving the color signal values required for the matching of the colors from a comparison of rated values and actual values.
11. A method according to claim 9 including the step of providing the color identification values as the standardized color values.
12. An arrangement for isochromatic simulation of a multi-colored reproduction on a color monitor, comprising:
a) signal source means for outputting color separation values Y,M,C,K of a multi-colored reproduction;
b) transformer stage means connected to said signal source means for transformation of said color separation values Y,M,C,K into color monitor video drive values required for the isochromatic simulation;
c) a color monitor means connected to receive said video drive values;
d) said transformer stage means comprising i) gradation stage means connected to said signal source means for changing the color separation values Y,M,C,K output by said sig-nal source means according to a reproduction gradation curve dependent on the later to occur reproduction process;
ii) an arithmetic stage means for calculation of color value triads r,g,b for a supporting point network of a reproduction color space;
iii) a supporting value memory means connected to said arithmetic stage means for deposit of the calculated color value triads of the supporting point network;
iv) an interpolation stage means communicating with said gradation stage means, arithmetic stage means, and supporting value memory means for interpolation of color value triads r,g,b from color value triads rn,bn,gn of said supporting point network dependent on altered color separation values Y', M', C' of the three chromatic color separations of the multi-colored reproduction;
v) logic stage means communicating with said interpolation stage means and gradation stage means for formation of corrected color value triads r', g', b' from the color value triads r,g,b and from color separa-tion values K' of a black separation;
vi) linearization stage means connected to said logic stage means for generating linearized color value triads rv, gv, bv from the color value triads r,g,b according to the radiation density characteristics of the color monitor means; and vii) analog-to-digital converter means communicating with the linearization stage means for generating video drive values r'v, g'v, b'v from the linearized color value triads rv, gv, bv
a) signal source means for outputting color separation values Y,M,C,K of a multi-colored reproduction;
b) transformer stage means connected to said signal source means for transformation of said color separation values Y,M,C,K into color monitor video drive values required for the isochromatic simulation;
c) a color monitor means connected to receive said video drive values;
d) said transformer stage means comprising i) gradation stage means connected to said signal source means for changing the color separation values Y,M,C,K output by said sig-nal source means according to a reproduction gradation curve dependent on the later to occur reproduction process;
ii) an arithmetic stage means for calculation of color value triads r,g,b for a supporting point network of a reproduction color space;
iii) a supporting value memory means connected to said arithmetic stage means for deposit of the calculated color value triads of the supporting point network;
iv) an interpolation stage means communicating with said gradation stage means, arithmetic stage means, and supporting value memory means for interpolation of color value triads r,g,b from color value triads rn,bn,gn of said supporting point network dependent on altered color separation values Y', M', C' of the three chromatic color separations of the multi-colored reproduction;
v) logic stage means communicating with said interpolation stage means and gradation stage means for formation of corrected color value triads r', g', b' from the color value triads r,g,b and from color separa-tion values K' of a black separation;
vi) linearization stage means connected to said logic stage means for generating linearized color value triads rv, gv, bv from the color value triads r,g,b according to the radiation density characteristics of the color monitor means; and vii) analog-to-digital converter means communicating with the linearization stage means for generating video drive values r'v, g'v, b'v from the linearized color value triads rv, gv, bv
13. An arrangement according to claim 12 wherein said logic stage means are designed as multipliers.
14. An arrangement according to claim 12 wherein a measuring stage means for color value triads r,g,b is provided, said measuring stage means being connected to outputs of said interpolation stage means and to said arithmetic stage means.
15. An arrangement according to claim 12 wherein an adjustable color generator means for prescription of color signal values is provided for generating colors on the color monitor means.
16. An arrangement according to claim 12 wherein following, additional circuit means are provided for automatic matching of the colors generated on the color monitor means to print corner colors, said circuit means com-prising:
a) a color measuring means allocated to said color monitor means for measuring standardized color values of colors generated on said color monitor as actual values;
b) a rated value memory means for deposit of the standardized color values of the print corner colors as rated values;
c) a control stage means connected to said color measuring means and to said rated value memory means for generating color signal values dependent on a comparison of rated values and actual values; and d) a modified color generator means comprising memory registers for color signal values which are connected to said control stage means and are connected to said gradation stage means.
a) a color measuring means allocated to said color monitor means for measuring standardized color values of colors generated on said color monitor as actual values;
b) a rated value memory means for deposit of the standardized color values of the print corner colors as rated values;
c) a control stage means connected to said color measuring means and to said rated value memory means for generating color signal values dependent on a comparison of rated values and actual values; and d) a modified color generator means comprising memory registers for color signal values which are connected to said control stage means and are connected to said gradation stage means.
17. An apparatus for isochromatic simulation of a multi-colored re-production on a color monitor wherein color separation values of a multi-colored reproduction to be represented are converted into video drive values for the color monitor which are required for the isochromatic simulation, comprising:
a) means for prescribing color signal values, generating colors corresponding to the prescribed color signal values on the color monitor, and matching the generated monitor colors to corner colors of a print color space by changing the color signal values, whereby the print corner colors have been printed under conditions of the multi-color reproduction;
b) means for identifying the color value triads r,g,b required for the chromatically coinciding generation of the corner colors on the color monitor given consideration of a non-linear relationship between radiation density values of individual phosphors of the color monitor and the color values;
c) means allocating for every corner color the identified color value triad r,g,b to a corresponding triad Y*,M*,C* of color separation values of three chromatic color separations of the corner color;
d) means for respectively calculating color value triads r,g,b for intermediate colors of the print color space lying between the corner colors required for chromatically coinciding generation of the intermediate colors on the color monitor from triads Y,M,C of the three chromatic color separations given consideration of the reproduction process for the multi-colored reproduction; and e) means allocating for every intermediate color the calculated color value triad r,g,b to the corresponding triad Y,M,C of color separation values of the three chromatic color separations of the intermediate color;
f) means for calling in and modifying color separation values Y,M,C,K of the three chromatic color separations and of a black separation of the multi-colored reproduction according to a reproduction gradation curve employed in the later to occur multi-color reproduction;
g) means for outputting the previously allocated color value triads r,g,b instead of color separation value triads Y',M',C' of the three chromatic color separations of the multi-colored reproduction;
h) means for combining the output color value triads r,g,b with the modified color separation values K' of the black separation to form cor-rected color value triads r',g',b'; and i) means for converting the corrected color value triads r',g',b' into video drive values r'v,g'v,b'v for the color monitor.
a) means for prescribing color signal values, generating colors corresponding to the prescribed color signal values on the color monitor, and matching the generated monitor colors to corner colors of a print color space by changing the color signal values, whereby the print corner colors have been printed under conditions of the multi-color reproduction;
b) means for identifying the color value triads r,g,b required for the chromatically coinciding generation of the corner colors on the color monitor given consideration of a non-linear relationship between radiation density values of individual phosphors of the color monitor and the color values;
c) means allocating for every corner color the identified color value triad r,g,b to a corresponding triad Y*,M*,C* of color separation values of three chromatic color separations of the corner color;
d) means for respectively calculating color value triads r,g,b for intermediate colors of the print color space lying between the corner colors required for chromatically coinciding generation of the intermediate colors on the color monitor from triads Y,M,C of the three chromatic color separations given consideration of the reproduction process for the multi-colored reproduction; and e) means allocating for every intermediate color the calculated color value triad r,g,b to the corresponding triad Y,M,C of color separation values of the three chromatic color separations of the intermediate color;
f) means for calling in and modifying color separation values Y,M,C,K of the three chromatic color separations and of a black separation of the multi-colored reproduction according to a reproduction gradation curve employed in the later to occur multi-color reproduction;
g) means for outputting the previously allocated color value triads r,g,b instead of color separation value triads Y',M',C' of the three chromatic color separations of the multi-colored reproduction;
h) means for combining the output color value triads r,g,b with the modified color separation values K' of the black separation to form cor-rected color value triads r',g',b'; and i) means for converting the corrected color value triads r',g',b' into video drive values r'v,g'v,b'v for the color monitor.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE3347049A DE3347049C2 (en) | 1983-12-24 | 1983-12-24 | Method and circuit arrangement for simulating multicolor printing on a color monitor |
| DEP3347049.9-51 | 1983-12-24 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1225149A true CA1225149A (en) | 1987-08-04 |
Family
ID=6218124
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000470818A Expired CA1225149A (en) | 1983-12-24 | 1984-12-21 | Method and circuit arrangement for simulating a multi- colored reproduction on a color monitor |
Country Status (8)
| Country | Link |
|---|---|
| US (1) | US4639770A (en) |
| EP (1) | EP0147813B1 (en) |
| JP (1) | JPH06103389B2 (en) |
| AT (1) | ATE56336T1 (en) |
| AU (1) | AU571623B2 (en) |
| CA (1) | CA1225149A (en) |
| DE (2) | DE3347049C2 (en) |
| SU (1) | SU1634146A3 (en) |
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| US4805013A (en) * | 1984-09-05 | 1989-02-14 | Canon Kabushiki Kaisha | Image data conversion system |
| US4758885A (en) * | 1985-06-17 | 1988-07-19 | Canon Kabushiki Kaisha | Method of processing color image |
| EP0243974B1 (en) * | 1986-05-01 | 1994-03-02 | Toppan Printing Co., Ltd. | Scanner set-up simulation apparatus |
| US4802007A (en) * | 1986-12-18 | 1989-01-31 | U.S. Philips Corporation | Picture pick-up and display system with electronic and printed picture display |
| EP0310829A3 (en) * | 1987-09-14 | 1990-02-28 | Toppan Printing Co., Ltd. | Pre-print simulation apparatus |
| JPH0785572B2 (en) * | 1987-09-22 | 1995-09-13 | 大日本スクリーン製造株式会社 | Color component conversion method in color reproduction of original color image |
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-
1983
- 1983-12-24 DE DE3347049A patent/DE3347049C2/en not_active Expired
-
1984
- 1984-12-19 US US06/683,803 patent/US4639770A/en not_active Expired - Lifetime
- 1984-12-20 EP EP84116006A patent/EP0147813B1/en not_active Expired - Lifetime
- 1984-12-20 DE DE8484116006T patent/DE3483148D1/en not_active Expired - Lifetime
- 1984-12-20 AT AT84116006T patent/ATE56336T1/en not_active IP Right Cessation
- 1984-12-21 AU AU37026/84A patent/AU571623B2/en not_active Ceased
- 1984-12-21 SU SU843826849A patent/SU1634146A3/en active
- 1984-12-21 CA CA000470818A patent/CA1225149A/en not_active Expired
- 1984-12-24 JP JP59271105A patent/JPH06103389B2/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| ATE56336T1 (en) | 1990-09-15 |
| SU1634146A3 (en) | 1991-03-07 |
| AU571623B2 (en) | 1988-04-21 |
| EP0147813A3 (en) | 1988-01-20 |
| DE3483148D1 (en) | 1990-10-11 |
| DE3347049A1 (en) | 1985-07-11 |
| AU3702684A (en) | 1985-07-04 |
| JPS60168146A (en) | 1985-08-31 |
| JPH06103389B2 (en) | 1994-12-14 |
| EP0147813A2 (en) | 1985-07-10 |
| EP0147813B1 (en) | 1990-09-05 |
| DE3347049C2 (en) | 1986-07-17 |
| US4639770A (en) | 1987-01-27 |
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