Patent EP0592146A2 successfully refreshed from Google Patents.
EP0592146A2
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EP
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Color reproduction method and apparatus
Assignee: Canon Information Systems Inc
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Filing: 1993-09-30
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Granted: —
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Expires: 2013-09-30
Abstract
Abstract Method and apparatus for color printing according to a printer table having high color smoothness for out-of-gamut colors. A color printer gamut edge is first determined and color primary values for colors within the printer gamut are calculated and inserted into the printer table. For transition colors, namely those colors outside the printer gamut edge but still within the printer table, color primary values are calculated by selecting a color from the printer gamut edge at a point which lies at a constant angle from the transition color in question. The same constant angle is used for each and every one of the transition colors. A border table is provided for colors outside of the printer table; the color primary values for the border table are selected in the same manner as for the transition colors. According to the invention, it is possible to provide smooth color transitions for out-of-gamut colors, and in particular it is possible to provide monotonically increasing lightness in both the printer table and the border table and thereby avoid undesirable bands of darker colors within lighter colors.
Inventors
- 👤 Brigitte Ruetz
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-09 12:29
CPC Classifications
H; H04; H04N; H04N1/00; H04N1/46; H04N1/56; H04N1/60; H04N1/6058
Claims Analysis
Total Claims: 25
Claim 1
Independent Claim
33 words
A color printer look-up table for providing color primary values corresponding to colors in device-independent color space, the color printer table having smoothly varying color values for colors outside the color printer gamut.
Claim 2
Dependent Claim
36 words
A color printer look-up table according to Claim 1, wherein colors outside the color printer gamut have monotonically increasing lightness from the darkest value in the printer table to the lightest value in the printer table.
Claim 3
Dependent Claim
35 words
A color printer look-up table according to Claim 1 or 2, wherein the color primary values include color primary values for colors inside the color printer gamut and for colors outside the color printer gamut.
Claim 4
Dependent Claim
25 words
A color printer look-up table according to Claim 3, wherein the color primary values include color primary values for colors within a color monitor gamut.
Claim 5
Dependent Claim
32 words
A color printer look-up table according to Claim 3 or 4, wherein for colors inside the color printer gamut, the color primary values are provided in accurate correspondence to the associated colors.
Claim 6
Dependent Claim
31 words
A color printer look-up table according to Claim 5, wherein the color primary values outside the color printer gamut are provided so as to preserve hue, increase saturation, and change lightness.
Claim 7
Dependent Claim
69 words
A color printer driver comprising: a printer table for providing color primary values corresponding to colors within the color printer gamut and for colors outside the color printer gamut, the color primary values varying smoothly for colors outside the color printer gamut; means for accepting a command for printing a designated color; and control means for extracting color primary values corresponding to the designated color from the printer table.
Claim 8
Dependent Claim
36 words
A color printer look-up table according to Claim 7, wherein colors outside the color printer gamut have monotonically increasing lightness from the darkest value in the printer table to the lightest value in the printer table.
Claim 9
Dependent Claim
25 words
A color printer driver according to Claim 7 or 8, wherein the printer table includes color primary values for colors within a color monitor gamut.
Claim 10
Dependent Claim
37 words
A color printer driver according to Claim 7, 8, 9 or 10 wherein for colors within the color printer gamut, the color primary values in the printer table are provided in accurate correspondence to the associated colors.
Claim 11
Dependent Claim
39 words
A color printer driver according to any of Claims 7 to 10, wherein the color primary values for colors in the printer table outside the printer gamut are provided so as to preserve hue, increase saturation, and change lightness.
Claim 12
Dependent Claim
62 words
A color printer driver according to any of Claims 7 to 11, further comprising a border table for providing color primary values for colors outside the printer table, wherein said control means selects the printer table or the border table based on the designated color and extracts color primary values from the selected one of the printer table and the border table.
Claim 13
Dependent Claim
25 words
A color printer driver according to Claim 12, wherein the border table is arranged in a wheel-like arrangement of cells centered on the lightness axis.
Claim 14
Dependent Claim
37 words
A color printer driver according to Claim 12 or 13, wherein the color primary values for colors in the border table outside the printer gamut are provided so as to preserve hue, increase saturation, and change lightness.
Claim 15
Independent Claim
68 words
A method for building a printer table comprising: determining a color printer gamut edge; mapping color primary values into the printer table for colors within the color printer gamut edge; and mapping transition colors into the printer table between the printer gamut edge and the edge of the printer table by constant angle extension to the edge of the printer gamut edge so as to increase color saturation.
Claim 16
Dependent Claim
37 words
A method according to Claim 15, further comprising the steps of mapping all points in a wedge subtended by the constant angle from the maximum saturation point of the printer gamut edge onto the maximum saturation point.
Claim 17
Dependent Claim
16 words
A method according to Claim 15 or 16, wherein the constant angle is substantially about 15°.
Claim 18
Dependent Claim
31 words
A method according to Claim 15, 16, 17 or 18, wherein the color primary values for transition colors in the printer table are provided for colors within a color monitor gamut.
Claim 19
Independent Claim
31 words
A method according to any of Claims 15 to 18, wherein for colors within the color printer gamut, the color primary values are provided in accurate correspondence to the associated colors.
Claim 20
Dependent Claim
27 words
A method according to Claim 19, wherein the color primary values outside the printer gamut are provided so as to preserve hue, increase saturation, and change lightness.
Claim 21
Independent Claim
19 words
A method according to any of Claims 15 to 20, further comprising the step of building a border table.
Claim 22
Dependent Claim
33 words
A method according to Claim 21, wherein the color primary values for colors in the border table outside the printer gamut are provided so as to preserve hue, increase saturation, and change lightness.
Claim 23
Independent Claim
40 words
A method of color image reproduction wherein not all desired colors are available via a desired output device, and wherein unavailable colors are mapped to respective available colors so as to preserve monotonic increases in lightness of the desired color.
Claim 24
Independent Claim
47 words
A method of color image reproduction wherein not all desired colors are available via a desired output device, and wherein unavailable colors are mapped to respective available colors so as to preserve an angle in color space between the desired color and a plane of constant luminance.
Claim 25
Dependent Claim
16 words
An image signal or recording generated using a method or apparatus according to any preceding claim.
References Cited (Backward Citations)
No citation records indexed.
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