Commit d532caae authored by Mark Oteiza's avatar Mark Oteiza

Add other D series white points and some simple conversions

* lisp/color.el (color-d75-xyz, color-d55-xyz, color-d50-xyz): New
constants.
(color-xyz-to-xyy, color-xyy-to-xyz, color-lab-to-lch):
(color-lch-to-lab): New functions.
parent 8d433d9b
......@@ -212,9 +212,18 @@ RED, GREEN and BLUE should be between 0.0 and 1.0, inclusive."
(* 12.92 b)
(- (* 1.055 (expt b (/ 2.4))) 0.055)))))
(defconst color-d75-xyz '(0.9497 1.0 1.2264)
"D75 white point in CIE XYZ.")
(defconst color-d65-xyz '(0.950455 1.0 1.088753)
"D65 white point in CIE XYZ.")
(defconst color-d55-xyz '(0.9568 1.0 0.9215)
"D55 white point in CIE XYZ.")
(defconst color-d50-xyz '(0.9642 1.0 0.8249)
"D50 white point in CIE XYZ.")
(defconst color-cie-ε (/ 216 24389.0))
(defconst color-cie-κ (/ 24389 27.0))
......@@ -269,6 +278,24 @@ conversion. If omitted or nil, use `color-d65-xyz'."
"Convert CIE L*a*b* to RGB."
(apply 'color-xyz-to-srgb (color-lab-to-xyz L a b)))
(defun color-xyz-to-xyy (X Y Z)
"Convert CIE XYZ to xyY."
(let ((d (float (+ X Y Z))))
(list (/ X d) (/ Y d) Y)))
(defun color-xyy-to-xyz (x y Y)
"Convert CIE xyY to XYZ."
(let ((y (float y)))
(list (/ (* Y x) y) Y (/ (* Y (- 1 x y)) y))))
(defun color-lab-to-lch (L a b)
"Convert CIE L*a*b* to L*C*h*"
(list L (sqrt (+ (* a a) (* b b))) (atan b a)))
(defun color-lch-to-lab (L C h)
"Convert CIE L*a*b* to L*C*h*"
(list L (* C (cos h)) (* C (sin h))))
(defun color-cie-de2000 (color1 color2 &optional kL kC kH)
"Return the CIEDE2000 color distance between COLOR1 and COLOR2.
Both COLOR1 and COLOR2 should be in CIE L*a*b* format, as
......
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