Method for conversion of a colour space using separate chromatic and luminance look-up tables
First Claim
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1. Method for converting the n components (xS, yS, SS) of a colour vector expressed in an n-dimensional source colour space into m components (RD, GD, Σ
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D) of this same vector expressed in an m-dimensional destination colour space, the said n components comprising a source luminance component (SS) and (n-1) source chromatic components (xS, yS), the said m components also comprising a destination luminance component (Σ
D) and (m-1) destination chromatic components (RD, GD),the said method comprising the following steps ;
finding an intermediate colour vector having, in the source color space, approximately the same chromatic components (xINT-CR=xS, yINT-CR=yS) as those (xS,yS) of said colour vector to be converted and a given luminance component (SINT-CR),interpolating the components (RINT-CR, GINT-CR, Σ
INT-CR) of this intermediate colour vector in the destination colour space,interpolating the luminance component (Σ
D) of this colour vector expressed in the destination colour space by using a normalized luminance look-up table comprising a plurality of pairs (SS-N, Σ
D-N) of values, where each pair comprises a normalized luminance component
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Abstract
According to the method,
- starting from the chromatic components xS, yS of the color vector to be converted, the components of an intermediate color vector RINT-CR, GINT-CR, ΣINT-CR are-interpolated, whose chromatic components, expressed in the source color space are: xINT-CR=xS, yINT-CR=yS;
- starting from the luminance component SS of the color vector to be converted and from the luminance component ΣINT-CR of the intermediate color vector, the luminance component ΣD of the converted color vector is interpolated;
- the chromatic components RD, GD of the converted color vector are calculated from its luminance component ΣD and from the components of the intermediate color vector RINT-CR, GINT-CR, ΣINT-CR. The conversion methods of the prior art are substantially improved.
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Citations
4 Claims
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1. Method for converting the n components (xS, yS, SS) of a colour vector expressed in an n-dimensional source colour space into m components (RD, GD, Σ
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D) of this same vector expressed in an m-dimensional destination colour space, the said n components comprising a source luminance component (SS) and (n-1) source chromatic components (xS, yS), the said m components also comprising a destination luminance component (Σ
D) and (m-1) destination chromatic components (RD, GD),the said method comprising the following steps ; finding an intermediate colour vector having, in the source color space, approximately the same chromatic components (xINT-CR=xS, yINT-CR=yS) as those (xS,yS) of said colour vector to be converted and a given luminance component (SINT-CR), interpolating the components (RINT-CR, GINT-CR, Σ
INT-CR) of this intermediate colour vector in the destination colour space,interpolating the luminance component (Σ
D) of this colour vector expressed in the destination colour space by using a normalized luminance look-up table comprising a plurality of pairs (SS-N, Σ
D-N) of values, where each pair comprises a normalized luminance component - View Dependent Claims (2, 3, 4)
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D) of this same vector expressed in an m-dimensional destination colour space, the said n components comprising a source luminance component (SS) and (n-1) source chromatic components (xS, yS), the said m components also comprising a destination luminance component (Σ
Specification