Patent US1216962A successfully refreshed from Google Patents.
Patent EP0570139A2 successfully refreshed from Google Patents.
EP0570139A2
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EP
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Method for forming colour images using hue-plus-gray colour model and error diffusion
Assignee: HP Inc
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Filing: 1993-04-30
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Granted: —
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Expires: 2013-04-30
Abstract
Abstract The invention is for use with a visible medium (73, 373) capable of light reflection etc., and for use with a colour-image source (42, 342) that defines a desired colour. Here a device (72, 372, 85-96) for causing the medium to appear coloured includes a gray-scale subsystem (K; 26, 96K) to achromatically suppress a stated fraction of the reflection ; and at least two device-primary subsystems (CMY[X] ; 27-29, 96C,96M, 96Y) to cause selective reflection of light of two associated device-primary colours. Even if the device, as originally made, in effect uses the gray-scale subsystem to help construct colours, or the device-primary subsystems to help form gray-scale "values", such cross-dependency is essentially removed. A programmed processor (43-55, 343-356, 357) resolves the desired-rendition information into Fraction-Black, Fraction-Colourant (N, N 1 , N 2 ), and hue (H). Fraction-Black (K) information is applied exclusively to control only the gray-scale subsystem (K); Fraction-Colourant (N) to control only the device-primary subsystem (CMY[X]) ; and hue (H) to select a dominant and a subordinate primary subsystem (C, MorY[X]) and as between them apportion the Fraction-Colourant (N). These parameters are used not only in colour selection but also in halftoning (62, 362), where they enable colourant choice at each pixel in terms of input colour rather than after resolution into pigment terms ; this capability is used to prevent colour artifacts such as pixels of pigment irrelevant to the desired colour.
Inventors
- 👤 Jeffrey S. Best
- 👤 Paul H. Dillinger
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-27 22:38
CPC Classifications
H; H04; H04N; H04N1/00; H04N1/46; H04N1/56; H04N1/60; H04N1/603; H04N1/52; H04N1/6058
Claims Analysis
Total Claims: 24
Claim 1
Independent Claim
141 words
A colour-halftoning method for actuating a colour-generating machine (72, 372; 85-96) to cause a visible medium (73,373) to appear coloured in correspondence with desired-colour information from a source (42, 342) of such desired colour information; said method comprising the steps of: receiving from the source the desired-colour information, and if it is not expressed in perceptual parameters (H, N, K; N j , N2 then resolving that information into perceptual parameters; then utilising the information, while it is expressed in terms of the perceptual parameters, to generate (62, 362) rendition-decision information (A) representing a specific colourant (RGBCMY[X]K; W) at each pixel location (21-25) of the machine, respectively; and applying (72, 87) that rendition-decision information to control the machine by selecting specific subsystems (26-29; 96K, 96C, 96M, 96Y) of the machine for actuation in relation to specific pixel locations (21, 25) respectively.
Claim 2
Dependent Claim
141 words
A colour-halftoning method for actuating a colour-generating machine (72, 372; 85-96) to cause a visible medium (73,373) to appear coloured in correspondence with desired-colour information from a source (42, 342) of such desired colour information; said method comprising the steps of: receiving from the source the desired-colour information, and if it is not expressed in perceptual parameters (H, N, K; N j , N2 then resolving that information into perceptual parameters; then utilising the information, while it is expressed in terms of the perceptual parameters, to generate (62, 362) rendition-decision information (A) representing a specific colourant (RGBCMY[X]K; W) at each pixel location (21-25) of the machine, respectively; and applying (72, 87) that rendition-decision information to control the machine by selecting specific subsystems (26-29; 96K, 96C, 96M, 96Y) of the machine for actuation in relation to specific pixel locations (21, 25) respectively.
Claim 3
Dependent Claim
121 words
The method of claim 1: further comprising, after the information-utilising step (62, 372), the step of restating (71,371) the specific colourant, at each pixel location (21-25), in terms of machine parameters (CMY[X]KW) if its perceptual expression is not correctly interpretable as already being in machine parameters; wherein said machine parameters correspond uniquely to separate physical colouring means (CMY[X]K;W) employed by the machine, and wherein the applying step comprises addressing independent control signals to actuate separate subsystems (26-29, 96K, 96C, 96M, 96Y) of the machine which are associated respectively with the separate physical colouring means and controllable with respect to said pixel locations; whereby the method effectuates a specific assignment of the separate physical colouring means (CMY[X]K;W) to each pixel location (21-25).
Claim 4
Dependent Claim
74 words
The method of claim 2, wherein the restating step comprises, for each pixel location: determining whether any single one of the separate physical colouring means (CMY[X]K;W) employed by the machine corresponds identically to the specific colourant as expressed in perceptual parameters (H, N, K, N 1 , N 2 ; RGBCMYKW); and if not, identifying a plurality of said physical means that does correspond identically to the specific colourant as expressed in perceptual parameters.
Claim 5
Dependent Claim
32 words
The method of claim 3, wherein: the separate physical colouring means (CMY[X]K;W) employed by the machine correspond one-to-one with elements (CMY[X]K;W) of the perceptual parameters (H, N, K; N 1 , N2).
Claim 6
Dependent Claim
18 words
The method of claim 2, wherein: the machine parameters (CMY[X]K;W) correspond one-to-one with elements of the perceptual parameters.
Claim 7
Dependent Claim
42 words
The method of claim 1, wherein the information-utilising step comprise the substep of: after generating said rendition-decision information (A) for each pixel (21), also determining (D-A) for that pixel a resulting colour error (new P) expressed in terms of said perceptual parameters.
Claim 8
Dependent Claim
51 words
The method of claim 6, wherein the information-utilising step comprises the further substep of: after the error-determining step for each pixel (21), also distributing the colour error (new P), expressed in terms of said perceptual parameters, to other specific pixels (22-25) for which the information-utilising step has not yet been performed.
Claim 9
Dependent Claim
105 words
The method of claim 7, further comprising: after the error-distributing substep, later performing said rendition-decision generating generation and then said error-determining substep and then said error-distributing substep many times cyclically in that order but with respect to said other specific pixels (22-25); and before each said later performance of the rendition-decision generation, first incorporating into said desired colour, for that pixel location (22-25), said colour error (new P) distributed to that pixel from other pixels (21) for which the error-distributing step was performed previously; said error incorporation being performed in terms of said perceptual parameters (H, N, K; N 1 , N 2 ; RGBCMYKW).
Claim 10
Dependent Claim
27 words
The method of claim 1, wherein: the applying step if performed in terms of machine parameters that are very closely correlated with elements of the perceptual parameters.
Claim 11
Dependent Claim
26 words
The method of claim 1, wherein: the applying step is performed in terms of machine parameters that are correlated one-to-one with elements of the perceptual parameters.
Claim 12
Dependent Claim
19 words
The method of claim 10, wherein: the machine parameters are substantially a subset of elements of the perceptual parameters.
Claim 13
Dependent Claim
64 words
The method of claim 16, wherein; the perceptual parameters are hue (H), Fraction-Colourant (M) and gray (K); the hue and Fraction-Colourant parameters considered together are expressed in terms of these elements: colourants red, green, blue, cyan, magenta and yellow (RGBCMY); the gray parameter is further resolved into these elements; black and white (KW); and the machine parameters are cyan, magenta, yellow, and black (CMYK).
Claim 14
Dependent Claim
257 words
A colour-halftoning method for actuating a colour-generating machine (72, 372; 85-96) to cause a visible medium (73, 373) to appear coloured in correspondence with desired-colour information from a source (42, 342) of such desired-colour information; said method comprising the steps of: receiving from the source the desired-colour information, and resolving the information into substantially hue (H), Fraction-Colourant (N) and gray (K), if such desired-colour information is not already so resolved; said hue, Fraction-Colourant and gray being expressed in terms of fractions of four active colourants, which are hereby defined for each pixel location of the machine as: - dominant primary (N 1 ) - subordinate primary (N 2 ) - black (K), and - white (W); then utilising the information, while it is thus resolved substantially into hue, Fraction-Colourant and gray, to generate rendition-decision information (A) substantially representing specific desired hue, Fraction-Colourant and gray at each pixel location (21) of the machine; wherein the rendition-decision information comprises selecting for use at each pixel location (21) a respective single colourant (RGBCMY[X]K;W) that can be implemented on the machine; then determining (D-A) a dispersible error (new P) resulting from use of said single colourant instead of substantially said desired hue, Fraction-Colourant and gray; then dispersing said error (new P) substantially in terms of hue, Fraction-Colourant and gray to selected other pixel locations (22-25) that are nearby; and after the information-utilising step, applying (87, 72) information related to the single selected colourant to select and actuate one or more specific corresponding subsystems (96K, 96C, 96M, 96Y; 26-29) of the machine.
Claim 15
Dependent Claim
257 words
A colour-halftoning method for actuating a colour-generating machine (72, 372; 85-96) to cause a visible medium (73, 373) to appear coloured in correspondence with desired-colour information from a source (42, 342) of such desired-colour information; said method comprising the steps of: receiving from the source the desired-colour information, and resolving the information into substantially hue (H), Fraction-Colourant (N) and gray (K), if such desired-colour information is not already so resolved; said hue, Fraction-Colourant and gray being expressed in terms of fractions of four active colourants, which are hereby defined for each pixel location of the machine as: - dominant primary (N 1 ) - subordinate primary (N 2 ) - black (K), and - white (W); then utilising the information, while it is thus resolved substantially into hue, Fraction-Colourant and gray, to generate rendition-decision information (A) substantially representing specific desired hue, Fraction-Colourant and gray at each pixel location (21) of the machine; wherein the rendition-decision information comprises selecting for use at each pixel location (21) a respective single colourant (RGBCMY[X]K;W) that can be implemented on the machine; then determining (D-A) a dispersible error (new P) resulting from use of said single colourant instead of substantially said desired hue, Fraction-Colourant and gray; then dispersing said error (new P) substantially in terms of hue, Fraction-Colourant and gray to selected other pixel locations (22-25) that are nearby; and after the information-utilising step, applying (87, 72) information related to the single selected colourant to select and actuate one or more specific corresponding subsystems (96K, 96C, 96M, 96Y; 26-29) of the machine.
Claim 16
Dependent Claim
232 words
The method of claim 13, wherein: said error-determining step comprises expressing the dispersible error (new P) in terms of fractions of primary colourants; said primary colourants being hereby defined as: - the chromatic colourants (CMYRGB[X]) and - black (K), and - white (W); said error-dispersing step comprises contributing a portion of each of said dispersible primary-colourant error fractions (new P) to each of said selected other pixel locations (22-25), respectively, substantially in accordance with a geometrical weighting pattern; the method comprises the further step of cumulating separately for each primary colourant, for each said other location, the error contributions (P) from all pixels contributing thereto; and the utilising step comprises, in generating said rendition-decision information for each particular pixel (21), the substeps of: further determining, from the desired-colour hue, Fraction-Colourant and gray, these additional elements of the desired colour: (a) identification of the desired dominant and subordinate chromatic primary colourants (RGBCMY[X]), and (b) the desired fractions (F) of all four active colourants; then, for said particular pixel, adding said desired fractions (F) of the four active colourants to that pixel's cumulated errors (P) for the corresponding four primary colourants, respectively, to determine (P + F) four respective composite errors (D) for that pixel (21) before printing; and then making a decision (A) to print, at said particular pixel (21), that one of the four active colourants which has highest composite error (D).
Claim 17
Dependent Claim
64 words
The method of claim 14, wherein: the error-determining step comprises establishing (P + F - A) the dispersible errors for said particular pixel as: said highest composite error (D) minus a value of unity (A), for the corresponding active colourant, and said respective composite errors (D) for the other three active primary colourants, and said respective cumulated errors (P) for the other primary colourants.
Claim 18
Dependent Claim
182 words
A colour-halftoning method for actuating a colour-generating machine (72, 372; 85-96) that employs a plurality of colourants (CMYK[X];W) to cause a visible medium (73, 373) to appear coloured in correspondence with desired-colour information from a source (42,342) of such desired-colour information; said method comprising the steps of: receiving from the source the desired-colour information; then utilising the information to generate (62, 362) rendition-decision information (A) representing a specific colourant (RGBCMY[X]K;W) at each pixel location (21-25) of the machine, respectively, including the substeps of: expressing the desired-colour information in terms (61,361) usable for constraining the number of colourants employed by the machine, and constraining the generation of rendition-decision information (D, A) to select only colourants having at least some specified degree of relationship (D = f[F]) to the input colour expressed in said terms; and applying (72, 87) that generated rendition-decision information (D) to: select (A = D max specific subsystems (26-29; 96K, 96C, 96M, 96Y) of the machine for actuation in relation to specific pixel locations (21), respectively, and actuate those specific subsystems (26-29; 96) in relation to specific pixel locations (21).
Claim 19
Dependent Claim
182 words
A colour-halftoning method for actuating a colour-generating machine (72, 372; 85-96) that employs a plurality of colourants (CMYK[X];W) to cause a visible medium (73, 373) to appear coloured in correspondence with desired-colour information from a source (42,342) of such desired-colour information; said method comprising the steps of: receiving from the source the desired-colour information; then utilising the information to generate (62, 362) rendition-decision information (A) representing a specific colourant (RGBCMY[X]K;W) at each pixel location (21-25) of the machine, respectively, including the substeps of: expressing the desired-colour information in terms (61,361) usable for constraining the number of colourants employed by the machine, and constraining the generation of rendition-decision information (D, A) to select only colourants having at least some specified degree of relationship (D = f[F]) to the input colour expressed in said terms; and applying (72, 87) that generated rendition-decision information (D) to: select (A = D max specific subsystems (26-29; 96K, 96C, 96M, 96Y) of the machine for actuation in relation to specific pixel locations (21), respectively, and actuate those specific subsystems (26-29; 96) in relation to specific pixel locations (21).
Claim 20
Dependent Claim
69 words
The method of claim 16, wherein: the expressing substep comprises identifying a second plurality of colourants (RYK; W--Fig. 23) into which the desired-colour information can be fully resolved; but which second plurality is smaller than the plurality of colourants (RGBCMYK;W) employed by the machine; and the constraining substep comprises using at least the identities of the colourants (RYK;W--Fig. 23) in said smaller plurality, in specifying said degree of relationship.
Claim 21
Dependent Claim
21 words
The method of claim 17, wherein: the smaller plurality is a subset of the plurality of colourants employed by the machine.
Claim 22
Dependent Claim
33 words
The method of claim 18, wherein: the constraining substep comprises limiting (A) the specific colourant, represented by the rendition-decision for each pixel location, to one of the identified colourants of said smaller plurality.
Claim 23
Dependent Claim
140 words
Apparatus for reproducing colour images in a medium comprising: a source (42, 342) of desired-colour information; a colour-generating machine (72, 372; 85-96) which can cause a visible medium (73, 373) to appear coloured in correspondence with said desired-colour information; means for receiving from the source the desired-colour information, and if it is not expressed in perceptual parameters (H, N, K; N 1 , N2 then resolving that information into perceptual parameters; means which utilises the information, while it is expressed in terms of the perceptual parameters, to generate (62, 362) rendition-decision information (A) representing a specific colourant (RGBCMY[X]K;W) at each pixel location (21-25) of the machine respectively; and wherein said machine is controlled by said rendition-decision information (A) by selecting specific subsystems (26-29; 96K, 96C, 96M, 96Y) of the machine for actuation in relation to specific pixel locations (21,25), respectively.
Claim 24
Dependent Claim
140 words
Apparatus for reproducing colour images in a medium comprising: a source (42, 342) of desired-colour information; a colour-generating machine (72, 372; 85-96) which can cause a visible medium (73, 373) to appear coloured in correspondence with said desired-colour information; means for receiving from the source the desired-colour information, and if it is not expressed in perceptual parameters (H, N, K; N 1 , N2 then resolving that information into perceptual parameters; means which utilises the information, while it is expressed in terms of the perceptual parameters, to generate (62, 362) rendition-decision information (A) representing a specific colourant (RGBCMY[X]K;W) at each pixel location (21-25) of the machine respectively; and wherein said machine is controlled by said rendition-decision information (A) by selecting specific subsystems (26-29; 96K, 96C, 96M, 96Y) of the machine for actuation in relation to specific pixel locations (21,25), respectively.
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