Display-based color system
First Claim
1. A method for defining an improved perceptually uniform color space for a display device, the improved perceptually uniform color space having coordinates H, V, and C, which are based upon CIELUV coordinates L*, v* and u*, the method comprising the steps of:
- (a) determining the maximum CIELUV chroma C*uv =(u*2 +v*2)1/2 producible by a display device that has a plurality of color-producing primaries, the luminous intensity of the primaries being adjustable between minimum and maximum levels to produce a gamut of colors;
(b) establishing a maximum numerical value for the C coordinate;
(c) dividing the maximum C value by the determined maximum CIELUV chroma to yield a chroma factor Cf ; and
(d) defining the improved color space coordinates as;
space="preserve" listing-type="equation">H=arctan (v*/u*)+K, whereK=0°
for u*>
0 and v*>
0;
K=90°
for u*<
0 and v*>
0;
K=180°
for u*<
0 and v*<
0;
K=270°
for u*>
0 and v*<
0;
space="preserve" listing-type="equation">V=L*;
space="preserve" listing-type="equation">C=C*.sub.uv (V)(C.sub.f).
5 Assignments
0 Petitions
Accused Products
Abstract
A method and apparatus for reversibly transforming color, which is selected from a gamut of colors producible by the primaries of a color display device (20), into a perceptually uniform color space. The coordinates of the color space are readily convertible into internationally accepted standards for color measurement. Also provided, is a method for transforming the color space coordinates of a selected color into the corresponding relative primary intensity levels of the display device (20).
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Citations
8 Claims
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1. A method for defining an improved perceptually uniform color space for a display device, the improved perceptually uniform color space having coordinates H, V, and C, which are based upon CIELUV coordinates L*, v* and u*, the method comprising the steps of:
-
(a) determining the maximum CIELUV chroma C*uv =(u*2 +v*2)1/2 producible by a display device that has a plurality of color-producing primaries, the luminous intensity of the primaries being adjustable between minimum and maximum levels to produce a gamut of colors; (b) establishing a maximum numerical value for the C coordinate; (c) dividing the maximum C value by the determined maximum CIELUV chroma to yield a chroma factor Cf ; and (d) defining the improved color space coordinates as;
space="preserve" listing-type="equation">H=arctan (v*/u*)+K,where K=0°
for u*>
0 and v*>
0;K=90°
for u*<
0 and v*>
0;K=180°
for u*<
0 and v*<
0;K=270°
for u*>
0 and v*<
0;
space="preserve" listing-type="equation">V=L*;
space="preserve" listing-type="equation">C=C*.sub.uv (V)(C.sub.f). - View Dependent Claims (2, 3, 4)
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5. A method for defining a selected color in terms of a perceptually uniform color space that is described by H, V, and C coordinates, the method comprising the steps of:
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(a) selecting a color that is defined by a primary intensity vector, which vector denoting the relative values of the luminous intensities of a plurality of primaries, each primary being adjustable to produce a range of luminous intensity levels; (b) generating a matrix for converting the primary intensity vector into corresponding XYZ tristimulus values; (c) multiplying the primary intensity of the selected color by the matrix to yield corresponding tristimulus values Xs, Ys, Zs ; (d) computing the CIELUV system coordinates L*, u*, v* that correspond to the tristimulus values Xs, Ys and Zs ; (e) computing the H coordinates as
space="preserve" listing-type="equation">H=arctan (v*/u*)+K,where K=0°
for u*>
0 and v*>
0;K=90°
for u*<
0 and v*>
0;K=180°
for u*<
0 and v*<
0;K=270°
for u*>
0 and v*<
0;(f) computing V as
space="preserve" listing-type="equation">V=L*;(g) computing Cf as 100/C*uvmax, where C*uvmax is the maximum numerical value of the CIELUV system chroma C*uv producible by the primaries; and (h) computing C as
space="preserve" listing-type="equation">C=(v*.sup.2 +u*.sup.2).sup.1/2 (V)(C.sub.f). - View Dependent Claims (6)
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7. A system for defining a color selected from a gamut of colors producible by a color display device in terms of a perceptually uniform color space that is described by H, V and C coordinates, the system comprising:
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(a) a display device having a plurality of primaries each primary variable between a minimum and maximum luminous intensity level for producing a color that is defined by a primary intensity vector denoting the relative values of the primary intensity levels; (b) input means for receiving and storing data corresponding to the primary intensity vector of the color; (c) processing means for (1) generating a matrix for converting primary intensity vectors into corresponding XYZ tristimulus values; (2) multiplying the primary intensity vector of the color by the matrix to yield the tristimulus values Xs, Ys, Zs of the color; (3) determining the L*, u* and v* coordinates of the CIELUV system that correspond to the tristimulus values Xs, Ys and Zs ; and (4) computing the H, V and C coordinates as;
space="preserve" listing-type="equation">H=(arctan (v*/u*)+K)-H.sub.0,where K=0°
for u*>
0 and v*>
0;K=90°
for u*<
0 and v*>
0;K=180°
for u*<
0 and v*<
0;K=270°
for u*>
0 and v*<
0;-11°
≦
H0 ≦
-15°
;V=L*; C=(v*2 +u*2)1/2 (V)(Cf) where Cf =100/C*uvmax, wherein C*uvmax is a maximum numerical value of the CIELUV chroma C*uv producible by the primaries of the display device. - View Dependent Claims (8)
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Specification