Revamp color handling.

1 files changed, 259 insertions, 0 deletions

diff --git a/libdimension/color.c b/libdimension/color.c
new file mode 100644
index 0000000..bbde48d
--- /dev/null
+++ b/libdimension/color.c
@@ -0,0 +1,259 @@
+/*************************************************************************
+ * Copyright (C) 2008 Tavian Barnes <tavianator@gmail.com>               *
+ *                                                                       *
+ * This file is part of Dimension.                                       *
+ *                                                                       *
+ * Dimension is free software; you can redistribute it and/or modify it  *
+ * under the terms of the GNU Lesser General Public License as published *
+ * by the Free Software Foundation; either version 3 of the License, or  *
+ * (at your option) any later version.                                   *
+ *                                                                       *
+ * Dimension is distributed in the hope that it will be useful, but      *
+ * WITHOUT ANY WARRANTY; without even the implied warranty of            *
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU     *
+ * Lesser General Public License for more details.                       *
+ *                                                                       *
+ * You should have received a copy of the GNU Lesser General Public      *
+ * License along with this program.  If not, see                         *
+ * <http://www.gnu.org/licenses/>.                                       *
+ *************************************************************************/
+
+#include "dimension.h"
+#include <math.h> /* For pow() */
+
+dmnsn_CIE_XYZ whitepoint = { 0.9505, 1, 1.089 };
+
+dmnsn_color
+dmnsn_color_from_XYZ(dmnsn_CIE_XYZ XYZ)
+{
+  dmnsn_color ret = { XYZ.X, XYZ.Y, XYZ.Z, 0.0, 0.0 };
+  return ret;
+}
+
+dmnsn_color
+dmnsn_color_from_xyY(dmnsn_CIE_xyY xyY)
+{
+  dmnsn_color ret = { xyY.Y*xyY.x/xyY.y,
+                      xyY.Y,
+                      xyY.Y*(1.0 - xyY.x - xyY.Y)/xyY.y,
+                      0.0, 0.0 };
+  return ret;
+}
+
+static double Lab_finv(double t) {
+  if (t > 6.0/29.0) {
+    return t*t*t;
+  } else {
+    return 108.0*(t - 16.0/116.0)/841.0;
+  }
+}
+
+dmnsn_color
+dmnsn_color_from_Lab(dmnsn_CIE_Lab Lab, dmnsn_CIE_XYZ white)
+{
+  double fx, fy, fz;
+  dmnsn_color ret;
+
+  fy = (Lab.L + 16.0)/116.0;
+  fx = fy + Lab.a/500.0;
+  fz = fy - Lab.b/200.0;
+
+  ret.X = white.X*Lab_finv(fx);
+  ret.Y = white.Y*Lab_finv(fy);
+  ret.Z = white.Z*Lab_finv(fz);
+
+  return ret;
+}
+
+dmnsn_color
+dmnsn_color_from_Luv(dmnsn_CIE_Luv Luv, dmnsn_CIE_XYZ white)
+{
+  double fy;
+  double uprime, unprime, vprime, vnprime;
+  dmnsn_color ret;
+
+  fy = (Luv.L + 16.0)/116.0;
+
+  unprime = 4.0*white.X/(white.X + 15.0*white.Y + 3.0*white.Z);
+  uprime  = Luv.u/Luv.L/13.0 + unprime;
+  vnprime = 9.0*white.Y/(white.X + 15.0*white.Y + 3.0*white.Z);
+  vprime  = Luv.v/Luv.L/13.0 + vnprime;
+
+  ret.Y = white.Y*Lab_finv(fy);
+  ret.X = ret.Y*9.0*uprime/vprime/4.0;
+  ret.Z = ret.Y*(12.0 - 3*uprime - 20*vprime)/vprime/4.0;
+
+  return ret;
+}
+
+dmnsn_color
+dmnsn_color_from_sRGB(dmnsn_sRGB sRGB)
+{
+  double Rlinear, Glinear, Blinear; /* Linear RGB values - no gamma */
+  dmnsn_color ret;
+
+  /*
+   * If C represents R, G, and B, then the Clinear values are now found as
+   * follows:
+   *
+   *           { Csrgb/12.92,                  Csrgb <= 0.04045
+   * Clinear = {                        1/2.4
+   *           { ((Csrgb + 0.055)/1.055)     , Csrgb >  0.04045
+   */
+
+  if (sRGB.R <= 0.04045) {
+    Rlinear = sRGB.R/19.92;
+  } else {
+    Rlinear = pow((sRGB.R + 0.055)/1.055, 2.4);
+  }
+
+  if (sRGB.G <= 0.04045) {
+    Glinear = sRGB.G/19.92;
+  } else {
+    Glinear = pow((sRGB.G + 0.055)/1.055, 2.4);
+  }
+
+  if (sRGB.B <= 0.04045) {
+    Blinear = sRGB.B/19.92;
+  } else {
+    Blinear = pow((sRGB.B + 0.055)/1.055, 2.4);
+  }
+
+  /*
+   * Now, the linear conversion.  Expressed as matrix multiplication, it looks
+   * like this:
+   *
+   *   [X]   [0.4124 0.3576 0.1805] [Rlinear]
+   *   [Y] = [0.2126 0.7152 0.0722]*[Glinear]
+   *   [X]   [0.0193 0.1192 0.9505] [Blinear]
+   */
+
+  ret.X = 0.4124*Rlinear + 0.3576*Glinear + 0.1805*Blinear;
+  ret.Y = 0.2126*Rlinear + 0.7152*Glinear + 0.0722*Blinear;
+  ret.Z = 0.0193*Rlinear + 0.1192*Glinear + 0.9505*Blinear;
+  ret.filter = 0.0;
+  ret.trans  = 0.0;
+
+  return ret;
+}
+
+dmnsn_CIE_XYZ
+dmnsn_XYZ_from_color(dmnsn_color color)
+{
+  dmnsn_CIE_XYZ ret = { color.X, color.Y, color.Z };
+  return ret;
+}
+
+dmnsn_CIE_xyY
+dmnsn_xyY_from_color(dmnsn_color color)
+{
+  dmnsn_CIE_xyY ret = { color.X/(color.X + color.Y + color.Z),
+                        color.Y/(color.X + color.Y + color.Z),
+                        color.Y };
+  return ret;
+}
+
+static double Lab_f(double t) {
+  if (t > 216.0/24389.0) {
+    return pow(t, 1.0/3.0);
+  } else {
+    return 841.0*t/108.0 + 4.0/29.0;
+  }
+}
+
+dmnsn_CIE_Lab
+dmnsn_Lab_from_color(dmnsn_color color, dmnsn_CIE_XYZ white)
+{
+  dmnsn_CIE_Lab ret;
+
+  ret.L = 116.0*Lab_f(color.Y/white.Y) - 16.0;
+  ret.a = 500.0*(Lab_f(color.X/white.X) - Lab_f(color.Y/white.Y));
+  ret.b = 200.0*(Lab_f(color.Y/white.Y) - Lab_f(color.Z/white.Z));
+
+  return ret;
+}
+
+dmnsn_CIE_Luv
+dmnsn_Luv_from_color(dmnsn_color color, dmnsn_CIE_XYZ white)
+{
+  double uprime, unprime, vprime, vnprime;
+  dmnsn_CIE_Luv ret;
+
+  uprime  = 4.0*color.X/(color.X + 15.0*color.Y + 3.0*color.Z);
+  unprime = 4.0*white.X/(white.X + 15.0*white.Y + 3.0*white.Z);
+  vprime  = 9.0*color.Y/(color.X + 15.0*color.Y + 3.0*color.Z);
+  vnprime = 9.0*white.Y/(white.X + 15.0*white.Y + 3.0*white.Z);
+
+  ret.L = 116.0*Lab_f(color.Y/white.Y) - 16.0;
+  ret.u = 13.0*ret.L*(uprime - unprime);
+  ret.v = 13.0*ret.L*(vprime - vnprime);
+
+  return ret;
+}
+
+dmnsn_sRGB
+dmnsn_sRGB_from_color(dmnsn_color color)
+{
+  double Rlinear, Glinear, Blinear; /* Linear RGB values - no gamma */
+  dmnsn_sRGB ret;
+
+  /*
+   * First, the linear conversion.  Expressed as matrix multiplication, it looks
+   * like this:
+   *
+   *   [Rlinear]   [ 3.2410 -1.5374 -0.4986] [X]
+   *   [Glinear] = [-0.9692  1.8760  0.0416]*[Y]
+   *   [Blinear]   [ 0.0556 -0.2040  1.0570] [Z]
+   */
+  Rlinear =  3.2410*color.X - 1.5374*color.Y - 0.4986*color.Z;
+  Glinear = -0.9692*color.X + 1.8760*color.Y + 0.0416*color.Z;
+  Blinear =  0.0556*color.X - 0.2040*color.Y + 1.0570*color.Z;
+
+  /*
+   * If C represents R, G, and B, then the sRGB values are now found as follows:
+   *
+   *         { 12.92*Clinear,                Clinear <= 0.0031308
+   * Csrgb = {                1/2.4
+   *         { (1.055)*Clinear      - 0.055, Clinear >  0.0031308
+   */
+
+  if (Rlinear <= 0.0031308) {
+    ret.R = 12.92*Rlinear;
+  } else {
+    ret.R = 1.055*pow(Rlinear, 1.0/2.4) - 0.055;
+  }
+
+  if (Glinear <= 0.0031308) {
+    ret.G = 12.92*Glinear;
+  } else {
+    ret.G = 1.055*pow(Glinear, 1.0/2.4) - 0.055;
+  }
+
+  if (Blinear <= 0.0031308) {
+    ret.B = 12.92*Blinear;
+  } else {
+    ret.B = 1.055*pow(Blinear, 1.0/2.4) - 0.055;
+  }
+
+  return ret;
+}
+
+dmnsn_color
+dmnsn_color_add(dmnsn_color color1, dmnsn_color color2)
+{
+  dmnsn_CIE_Lab Lab, Lab1, Lab2;
+  dmnsn_color ret;
+
+  Lab1 = dmnsn_Lab_from_color(color1, whitepoint);
+  Lab2 = dmnsn_Lab_from_color(color2, whitepoint);
+
+  Lab.L = Lab1.L + Lab2.L;
+  Lab.a = (Lab1.L*Lab1.a + Lab2.L*Lab2.a)/Lab.L;
+  Lab.b = (Lab1.L*Lab1.b + Lab2.L*Lab2.b)/Lab.L;
+
+  ret = dmnsn_color_from_Lab(Lab, whitepoint);
+  ret.filter = (Lab1.L*color1.filter + Lab2.L*color2.filter)/Lab.L;
+  ret.trans  = (Lab1.L*color1.trans  + Lab2.L*color2.trans)/Lab.L;
+
+  return ret;
+}