Patent AT109229B successfully refreshed from Google Patents.
Patent EP0488656A2 successfully refreshed from Google Patents.
EP0488656A2
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EP
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Colour transformation method
Assignee: Konica Minolta Inc
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Filing: 1991-11-26
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Granted: —
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Expires: 2011-11-26
Abstract
Abstract The invention provides a method of transforming color image data of first media (color hardcopy) so as to be reproduced by second media (color CRT), the color reproducing capability of which is larger than that of the first media. The chroma of color image data "T" is compared with a threshold value which is "a" (a < 1.0) times of the maximum chroma of the first color gamut of the first media at the lightness "LT" and the hue "ϑT" of the color image data "T". The chroma "rT" is enlarge in accordance with the comparison result without changing the hue "ϑT".
Inventors
- 👤 Toru Konica Corporation Hoshino
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-03 14:06
CPC Classifications
H; H04; H04N; H04N1/00; H04N1/46; H04N1/56; H04N1/60; H04N1/6058
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
447 words
A method for transforning color image data of first media so as to be reproduced by second media, the color reproducing capability of which is larger than that of the first media, comprising: obtaining a first colour gamut (or range) on a colourimetric system on the basis of a plurality of color image data of the first media beforehand, the colorimetric system being one of the CIE standard L*u*v* and L*a*b* color systems; obtaining a second colour gamut (or range) on the colourimetric system on the basis of a plurality of color image data of the second media; calculating the first lightness difference between the maximum and minimum values of the lightness on the lightness axis of the first color gamut, the second lightness difference between them of the seond color gamut, and the lightness defference ratio of the first light difference to the second lightness difference; inputting image data of the first media; converting the L* value of a color image data "T" of the first media on the basis of the lightness difference ratio; assuming a line passing the lightness "LT" and the chroma "rT" of the color image data "T" while keeping the hue "ϑT" of the color image data "T"; obtaining the maximum chroma "r1max" on the line of the first color gamut and the maximum chroma "r2max" on the line of the second color gamut; comparing the chroma "rT" of the color image data "T" with a threshold value which is "a" (a < 1.0) times of the maximum chroma "r1max" of the first color gamut; and in the case that the chroma "rT" is not larger than the threshold value, using the u* and v* values or the a* and b* values of the color image data "T" without any change, or in the case that the chroma "rT" is larger than the threshold value, calculating the first chroma difference between the maximum chroma "r1max" in the first color gamut and the threshold value, the second chroma difference between the maximum chroma "r2max" in the second color gamut and the threshold value, and the chroma difference ratio of the first chroma difference to the second chroma difference, converting the chroma "rT" on the basis of the chroma difference ratio, converting the u* and v* values or the a* and b* values of the color image data "T" so as to obtain the converted chroma without changing the hue "ϑT", and converting further the L* value of the color image data "T" in accordance with the conversion amount of the chroma so as to increase the lightness in accordance with the increases of the chroma at least in a high lightness region.
Claim 2
Dependent Claim
92 words
The method of claim 1, when u* and v* or a* and b* at the maximum lightness point of the first color gamut are different from u* and v* or a* and b* at the maximum lightness point of the second color gamut, futher comprising moving u* and v* or a* and b* of a color image data of the first media, at least in a high lightness region, in accordance with the movement distance from the maximum lightness points of the first color gamut to that of the second color gamuts.
Claim 3
Independent Claim
407 words
A method for transforming color image data of first media so as to be reproduced by second media, the color reproducing capability of which is larger than that of the first media, comprising: obtaining a first colour gamut (or range) on a colourimetric system on the basis of a plurality of color image data of the first media beforehand, the colorimetric system being one of L*u*v* and L*a*b* color systems; obtaining a second colour gamut (or range) on the colourimetric system on the basis of a plurality of color image data of the second media beforehand; calculating the first lightness difference between the maximum and minimum values of the lightness on the lightness axis of the first color gamut, the second lightness difference between them of the seond color gamut, and the lightness defference ratio between the first and second lightness differences in advance; inputting image data of the first media; converting the L* value of a color image data "T" of the first media on the basis of the lightness difference ratio; comparing the chroma "rT" of the color image data "T" of the first media with a threshold value which is "a" (a < 1.0) times of the maximum chroma "r1max" of the first color gamut at the lightness "LT" and the hue "ϑT" of the color image data "T" ; and in the case that the chroma "rT" is not larger than the threshold value, using the u* and v* values or the a* and b* values of the color image data "T" without any change, or in the case that the chroma "rT" is larger than the threshold value, assuming a first region enclosed between the inner gamut surface which comprises a value which is "a" (a < 1.0) times of the maximum chroma of each of hue and lightness of the first color gamut and the outer surface of the first color gamut which comprises the maximum chroma of each of the hue and the lightness of the first color gamut, and a second region enclosed between the inner gamut surface abovementioned and the outer surface of the second color gamut which comprises the maximum chroma value of each of the hue and the lightness of the second color gamut; converting the u* and v* values or the a* and b* values of the color image data "T" so as to make the first region in continuous adaption with the second region.
Claim 4
Dependent Claim
70 words
The method of claim 3, wherein, when the chroma "rT" increases and when the hue "ϑT" locates within one of predetermined regions each neighboring the hue having the maximum chroma of each of blue, green, red, yellow, magenta and cyan in the first color gamut, the hue "ϑT" is moved in a direction toward to the hue having the maximum chroma of the same color of the second color gamut.
Claim 5
Dependent Claim
77 words
The method of claim 3, wherein, when the chroma "rT" increases and when the hue "ϑT" locates within one of predetermined regions each neighboring the hue having the maximum chroma of each of three primary colors of the first color gamut, the hue "ϑT" is moved in a direction toward to one of two hues, which are short distance from the abovementioned hue, having the maximum chroma of the three primary colors of the second color gamut.
Claim 6
Dependent Claim
92 words
The method of claim 3, when u* and v* or a* and b* at the maximum lightness point of the first color gamut are different from u* and v* or a* and b* at the maximum lightness point of the second color gamut, further comprising moving u* and v* or a* and b* of a color image data of the first media, at least in a high lightness region, in accordance with the movement distance from the maximum lightness point of the first color gamut to that of the second color gamut.
Claim 7
Dependent Claim
19 words
An image display device adapted to operate in accordance with the method of any one of the preceding claims.
References Cited (Backward Citations)
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