Revamp color handling.

10 files changed, 428 insertions, 237 deletions

diff --git a/libdimension-png/png.c b/libdimension-png/png.c
index 750b5af..dbcd21a 100644
--- a/libdimension-png/png.c
+++ b/libdimension-png/png.c
@@ -32,7 +32,8 @@ dmnsn_png_write_canvas(const dmnsn_canvas *canvas, FILE *file)
   png_uint_32 width, height;
   unsigned int x, y;
   uint16_t *row = NULL;
-  dmnsn_pixel *pixel;
+  dmnsn_color *pixel;
+  dmnsn_sRGB sRGB;
 
   width = canvas->x;
   height = canvas->y;
@@ -80,16 +81,27 @@ dmnsn_png_write_canvas(const dmnsn_canvas *canvas, FILE *file)
     for (x = 0; x < width; ++x) {
       /* Invert the rows.  PNG coordinates are fourth quadrant. */
       pixel = canvas->pixels + (height - y - 1)*width + x;
+      sRGB = dmnsn_sRGB_from_color(*pixel);
 
-      row[4*x] = pixel->r;
-      row[4*x + 1] = pixel->g;
-      row[4*x + 2] = pixel->b;
+      if (sRGB.R < 1.0) {
+        row[4*x] = sRGB.R*UINT16_MAX;
+      } else {
+        row[4*x] = UINT16_MAX;
+      }
 
-      if (pixel->a > pixel->t) {
-        row[4*x + 3] = pixel->a;
+      if (sRGB.G < 1.0) {
+        row[4*x + 1] = sRGB.G*UINT16_MAX;
+      } else {
+        row[4*x + 1] = UINT16_MAX;
+      }
+      
+      if (sRGB.B < 1.0) {
+        row[4*x + 2] = sRGB.B*UINT16_MAX;
       } else {
-        row[4*x + 3] = pixel->t;
+        row[4*x + 2] = UINT16_MAX;
       }
+
+      row[4*x + 3] = (pixel->filter + pixel->trans)*UINT16_MAX;
     }
     png_write_row(png_ptr, (png_bytep)row);
   }
@@ -112,7 +124,8 @@ dmnsn_png_read_canvas(dmnsn_canvas **canvas, FILE *file)
   png_bytep image = NULL;
   png_bytep *row_pointers = NULL;
   unsigned int x, y;
-  dmnsn_pixel *pixel;
+  dmnsn_color *pixel;
+  dmnsn_sRGB sRGB;
   png_bytep png_pixel;
 
   /* Ensure that *canvas can always be deleted. */
@@ -203,11 +216,18 @@ dmnsn_png_read_canvas(dmnsn_canvas **canvas, FILE *file)
           pixel = (*canvas)->pixels + (height - y - 1)*width + x;
           png_pixel = image + 8*(y*width + x);
 
-          pixel->r = (png_pixel[0] << UINT16_C(8)) + png_pixel[1];
-          pixel->g = (png_pixel[2] << UINT16_C(8)) + png_pixel[3];
-          pixel->b = (png_pixel[4] << UINT16_C(8)) + png_pixel[5];
-          pixel->a = (png_pixel[6] << UINT16_C(8)) + png_pixel[7];
-          pixel->t = 0;
+          sRGB.R = ((double)((png_pixel[0] << UINT16_C(8)) + png_pixel[1]))
+            /UINT16_MAX;
+          sRGB.G = ((double)((png_pixel[2] << UINT16_C(8)) + png_pixel[3]))
+            /UINT16_MAX;
+          sRGB.B = ((double)((png_pixel[4] << UINT16_C(8)) + png_pixel[5]))
+            /UINT16_MAX;
+
+          *pixel = dmnsn_color_from_sRGB(sRGB);
+
+          pixel->filter = 0.0;
+          pixel->trans  = ((double)((png_pixel[6] << UINT16_C(8))
+                                    + png_pixel[7]))/UINT16_MAX;
         }
       }
     } else {
@@ -216,11 +236,17 @@ dmnsn_png_read_canvas(dmnsn_canvas **canvas, FILE *file)
           pixel = (*canvas)->pixels + (height - y - 1)*width + x;
           png_pixel = image + 6*(y*width + x);
 
-          pixel->r = (png_pixel[0] << UINT16_C(8)) + png_pixel[1];
-          pixel->g = (png_pixel[2] << UINT16_C(8)) + png_pixel[3];
-          pixel->b = (png_pixel[4] << UINT16_C(8)) + png_pixel[5];
-          pixel->a = 0;
-          pixel->t = 0;
+          sRGB.R = ((double)((png_pixel[0] << UINT16_C(8)) + png_pixel[1]))
+            /UINT16_MAX;
+          sRGB.G = ((double)((png_pixel[2] << UINT16_C(8)) + png_pixel[3]))
+            /UINT16_MAX;
+          sRGB.B = ((double)((png_pixel[4] << UINT16_C(8)) + png_pixel[5]))
+            /UINT16_MAX;
+
+          *pixel = dmnsn_color_from_sRGB(sRGB);
+
+          pixel->filter = 0.0;
+          pixel->trans  = 0.0;
         }
       }
     }
@@ -232,11 +258,14 @@ dmnsn_png_read_canvas(dmnsn_canvas **canvas, FILE *file)
           pixel = (*canvas)->pixels + (height - y - 1)*width + x;
           png_pixel = image + 4*(y*width + x);
 
-          pixel->r = png_pixel[0] << UINT16_C(8);
-          pixel->g = png_pixel[1] << UINT16_C(8);
-          pixel->b = png_pixel[2] << UINT16_C(8);
-          pixel->a = png_pixel[3] << UINT16_C(8);
-          pixel->t = 0;
+          sRGB.R = ((double)png_pixel[0])/UINT8_MAX;
+          sRGB.G = ((double)png_pixel[1])/UINT8_MAX;
+          sRGB.B = ((double)png_pixel[2])/UINT8_MAX;
+
+          *pixel = dmnsn_color_from_sRGB(sRGB);
+
+          pixel->filter = 0.0;
+          pixel->trans  = ((double)png_pixel[3])/UINT8_MAX;
         }
       }
     } else {
@@ -245,11 +274,14 @@ dmnsn_png_read_canvas(dmnsn_canvas **canvas, FILE *file)
           pixel = (*canvas)->pixels + (height - y - 1)*width + x;
           png_pixel = image + 3*(y*width + x);
 
-          pixel->r = png_pixel[0] << UINT16_C(8);
-          pixel->g = png_pixel[1] << UINT16_C(8);
-          pixel->b = png_pixel[2] << UINT16_C(8);
-          pixel->a = 0;
-          pixel->t = 0;
+          sRGB.R = ((double)png_pixel[0])/UINT8_MAX;
+          sRGB.G = ((double)png_pixel[1])/UINT8_MAX;
+          sRGB.B = ((double)png_pixel[2])/UINT8_MAX;
+
+          *pixel = dmnsn_color_from_sRGB(sRGB);
+
+          pixel->filter = 0.0;
+          pixel->trans  = 0.0;
         }
       }
     }
diff --git a/libdimension/Makefile.am b/libdimension/Makefile.am
index 293093c..9338b38 100644
--- a/libdimension/Makefile.am
+++ b/libdimension/Makefile.am
@@ -21,5 +21,5 @@ nobase_include_HEADERS = dimension.h dimension/geometry.h dimension/color.h dime
 
 lib_LTLIBRARIES = libdimension.la
 
-libdimension_la_SOURCES = dimension.h dimension/geometry.h dimension/color.h dimension/canvas.h canvas.c
+libdimension_la_SOURCES = dimension.h dimension/geometry.h dimension/color.h dimension/canvas.h canvas.c color.c inlines.c
 libdimension_la_LDFLAGS = -version-info 0:0:0
diff --git a/libdimension/canvas.c b/libdimension/canvas.c
index 4e3f89f..21d6d86 100644
--- a/libdimension/canvas.c
+++ b/libdimension/canvas.c
@@ -19,169 +19,7 @@
  *************************************************************************/
 
 #include "dimension.h"
-#include <math.h>
-#include <stdlib.h>
-
-/* Conversions between CIE 1931 XYZ and sRGB color. */
-
-dmnsn_pixel
-dmnsn_pixel_from_color(dmnsn_color color)
-{
-  double X, Y, Z;                   /* CIE XYZ values */
-  double Rlinear, Glinear, Blinear; /* Linear RGB values - no gamma */
-  double R, G, B;                   /* sRGB values */
-  dmnsn_pixel pixel;
-
-  /* Convert from CIE xyY to CIE XYZ */
-  Y = color.Y;
-  X = Y*color.x/color.y;
-  Z = Y*(1.0 - color.x - color.y)/color.y;
-
-  /*
-   * 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*X - 1.5374*Y - 0.4986*Z;
-  Glinear = -0.9692*X + 1.8760*Y + 0.0416*Z;
-  Blinear =  0.0556*X - 0.2040*Y + 1.0570*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) {
-    R = 12.92*Rlinear;
-  } else {
-    R = 1.055*pow(Rlinear, 1.0/2.4) - 0.055;
-  }
-
-  if (Glinear <= 0.0031308) {
-    G = 12.92*Glinear;
-  } else {
-    G = 1.055*pow(Glinear, 1.0/2.4) - 0.055;
-  }
-
-  if (Blinear <= 0.0031308) {
-    B = 12.92*Blinear;
-  } else {
-    B = 1.055*pow(Blinear, 1.0/2.4) - 0.055;
-  }
-
-  /* Now we go from unlimited to limited light, saturating at UINT16_MAX */
-
-  if (R < 0.0) {
-    pixel.r = 0.0;
-  } else if (R > 1.0) {
-    pixel.r = UINT16_MAX;
-  } else {
-    pixel.r = UINT16_MAX*R;
-  }
-
-  if (G < 0.0) {
-    pixel.g = 0.0;
-  } else if (G > 1.0) {
-    pixel.g = UINT16_MAX;
-  } else {
-    pixel.g = UINT16_MAX*G;
-  }
-
-  if (B < 0.0) {
-    pixel.b = 0.0;
-  } else if (B > 1.0) {
-    pixel.b = UINT16_MAX;
-  } else {
-    pixel.b = UINT16_MAX*B;
-  }
-
-  if (color.filter < 0.0) {
-    pixel.a = 0.0;
-  } else if (color.filter > 1.0) {
-    pixel.a = UINT16_MAX;
-  } else {
-    pixel.a = UINT16_MAX*color.filter;
-  }
-
-  if (color.trans < 0.0) {
-    pixel.t = 0.0;
-  } else if (color.trans > 1.0) {
-    pixel.t = UINT16_MAX;
-  } else {
-    pixel.t = UINT16_MAX*color.trans;
-  }
-
-  return pixel;
-}
-
-dmnsn_color
-dmnsn_color_from_pixel(dmnsn_pixel pixel)
-{
-  double R, G, B;                   /* sRGB values */
-  double Rlinear, Glinear, Blinear; /* Linear RGB values - no gamma */
-  double X, Y, Z;                   /* CIE XYZ values */
-  dmnsn_color color;
-
-  /* Conversion back to unlimited light */
-  R = ((double)pixel.r)/UINT16_MAX;
-  G = ((double)pixel.g)/UINT16_MAX;
-  B = ((double)pixel.b)/UINT16_MAX;
-
-  /*
-   * 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 (R <= 0.04045) {
-    Rlinear = R/19.92;
-  } else {
-    Rlinear = pow((R + 0.055)/1.055, 2.4);
-  }
-
-  if (G <= 0.04045) {
-    Glinear = G/19.92;
-  } else {
-    Glinear = pow((G + 0.055)/1.055, 2.4);
-  }
-
-  if (B <= 0.04045) {
-    Blinear = B/19.92;
-  } else {
-    Blinear = pow((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]
-   */
-
-  X = 0.4124*Rlinear + 0.3576*Glinear + 0.1805*Blinear;
-  Y = 0.2126*Rlinear + 0.7152*Glinear + 0.0722*Blinear;
-  Z = 0.0193*Rlinear + 0.1192*Glinear + 0.9505*Blinear;
-
-  /* Now convert to CIE xyY colorspace */
-  color.x = X/(X + Y + Z);
-  color.y = Y/(X + Y + Z);
-  color.Y = Y;
-  color.filter = ((double)pixel.a)/UINT16_MAX;
-  color.trans = ((double)pixel.t)/UINT16_MAX;
-
-  return color;
-}
+#include <stdlib.h> /* For malloc(), free() */
 
 dmnsn_canvas *
 dmnsn_new_canvas(unsigned int x, unsigned int y)
@@ -191,7 +29,7 @@ dmnsn_new_canvas(unsigned int x, unsigned int y)
   if (canvas) {
     canvas->x = x;
     canvas->y = y;
-    canvas->pixels = malloc(sizeof(dmnsn_pixel)*x*y);
+    canvas->pixels = malloc(sizeof(dmnsn_color)*x*y);
 
     if (canvas->pixels) {
       return canvas;
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;
+}
diff --git a/libdimension/dimension.h b/libdimension/dimension.h
index 558c9ed..c52ae31 100644
--- a/libdimension/dimension.h
+++ b/libdimension/dimension.h
@@ -28,6 +28,10 @@
 extern "C" {
 #endif
 
+#ifndef DMNSN_INLINE
+#define DMNSN_INLINE extern inline
+#endif
+
 #include <dimension/geometry.h>
 #include <dimension/color.h>
 #include <dimension/canvas.h>
diff --git a/libdimension/dimension/canvas.h b/libdimension/dimension/canvas.h
index 8959e12..21d56e4 100644
--- a/libdimension/dimension/canvas.h
+++ b/libdimension/dimension/canvas.h
@@ -25,15 +25,6 @@
 #ifndef DIMENSION_CANVAS_H
 #define DIMENSION_CANVAS_H
 
-/* 48-bit sRGB color for pixels. */
-typedef struct {
-  uint16_t r, g, b; /* Red, green, blue */
-  uint16_t a, t;    /* Filtered transparancy, normal transparancy */
-} dmnsn_pixel;
-
-dmnsn_pixel dmnsn_pixel_from_color(dmnsn_color color);
-dmnsn_color dmnsn_color_from_pixel(dmnsn_pixel pixel);
-
 typedef struct {
   unsigned int x, y;
 
@@ -41,7 +32,7 @@ typedef struct {
    * Stored in first-quadrant representation (origin is bottom-left).  The pixel
    * at (a,b) is accessible as pixels[b*x + a].
    */
-  dmnsn_pixel *pixels;
+  dmnsn_color *pixels;
 } dmnsn_canvas;
 
 dmnsn_canvas *dmnsn_new_canvas(unsigned int x, unsigned int y);
diff --git a/libdimension/dimension/color.h b/libdimension/dimension/color.h
index 34668e3..d637a81 100644
--- a/libdimension/dimension/color.h
+++ b/libdimension/dimension/color.h
@@ -29,16 +29,57 @@
 extern "C" {
 #endif
 
-/* CIE 1931 xyY color. */
+/* Internally, we use CIE 1931 XYZ color. */
+typedef struct {
+  double X, Y, Z;
+  double filter, trans; /* Filter transparancy only lets light of this color
+                           through; regular transparancy lets all colors
+                           through.  filter + trans should be <= 1.0. */
+} dmnsn_color;
+
+typedef struct {
+  double X, Y, Z; /* X, Y, and Z are tristimulus values, unbounded above zero.
+                     Diffuse white is (0.9505, 1, 1.089). */
+} dmnsn_CIE_XYZ;
+
 typedef struct {
   double x, y, Y; /* x and y are chromaticity coordinates, and Y is luminance,
                      in the CIE 1931 xyZ color space.  We use an unlimited light
                      model, so x,y in [0, 1] and Y >= 0, with 1 = diffuse
                      white */
-  double filter, trans; /* Filter transparancy only lets light of this color
-                           through; regular transparancy lets all colors
-                           through */
-} dmnsn_color;
+} dmnsn_CIE_xyY;
+
+typedef struct {
+  double L, a, b; /* L is luminence (100 = diffuse white); a and b are color-
+                     opponent dimensions.  This color space is used for color
+                     arithmetic. */
+} dmnsn_CIE_Lab;
+
+typedef struct {
+  double L, u, v; /* L is luminence (100 = diffuse white); u and v are
+                     chromaticity coordinates. */
+} dmnsn_CIE_Luv;
+
+typedef struct {
+  double R, G, B; /* sRGB R, G, and B values */
+} dmnsn_sRGB;
+
+/* Standard whitepoint, determined by the conversion of sRGB white to XYZ */
+extern dmnsn_CIE_XYZ whitepoint;
+
+dmnsn_color dmnsn_color_from_XYZ(dmnsn_CIE_XYZ XYZ);
+dmnsn_color dmnsn_color_from_xyY(dmnsn_CIE_xyY xyY);
+dmnsn_color dmnsn_color_from_Lab(dmnsn_CIE_Lab Lab, dmnsn_CIE_XYZ white);
+dmnsn_color dmnsn_color_from_Luv(dmnsn_CIE_Luv Luv, dmnsn_CIE_XYZ white);
+dmnsn_color dmnsn_color_from_sRGB(dmnsn_sRGB sRGB);
+
+dmnsn_CIE_XYZ dmnsn_XYZ_from_color(dmnsn_color color);
+dmnsn_CIE_xyY dmnsn_xyY_from_color(dmnsn_color color);
+dmnsn_CIE_Lab dmnsn_Lab_from_color(dmnsn_color color, dmnsn_CIE_XYZ white);
+dmnsn_CIE_Luv dmnsn_Luv_from_color(dmnsn_color color, dmnsn_CIE_XYZ white);
+dmnsn_sRGB    dmnsn_sRGB_from_color(dmnsn_color color);
+
+dmnsn_color dmnsn_color_add(dmnsn_color color1, dmnsn_color color2);
 
 #ifdef __cplusplus
 }
diff --git a/libdimension/dimension/geometry.h b/libdimension/dimension/geometry.h
index 2c0c204..11a6daf 100644
--- a/libdimension/dimension/geometry.h
+++ b/libdimension/dimension/geometry.h
@@ -31,44 +31,44 @@ typedef struct { dmnsn_scalar x, y, z; } dmnsn_vector;
 
 /* Vector arithmetic */
 
-inline dmnsn_vector
+DMNSN_INLINE dmnsn_vector
 dmnsn_vector_construct(dmnsn_scalar x, dmnsn_scalar y, dmnsn_scalar z)
 {
   dmnsn_vector v = { .x = x, .y = y, .z = z };
   return v;
 }
 
-inline dmnsn_vector
+DMNSN_INLINE dmnsn_vector
 dmnsn_vector_add(dmnsn_vector lhs, dmnsn_vector rhs)
 {
   return dmnsn_vector_construct(lhs.x + rhs.x, lhs.y + rhs.y, lhs.z + rhs.z);
 }
 
-inline dmnsn_vector
+DMNSN_INLINE dmnsn_vector
 dmnsn_vector_sub(dmnsn_vector lhs, dmnsn_vector rhs)
 {
   return dmnsn_vector_construct(lhs.x - rhs.x, lhs.y - rhs.y, lhs.z - rhs.z);
 }
 
-inline dmnsn_vector
+DMNSN_INLINE dmnsn_vector
 dmnsn_vector_mul(dmnsn_scalar lhs, dmnsn_vector rhs)
 {
   return dmnsn_vector_construct(lhs*rhs.x, lhs*rhs.y, lhs*rhs.z);
 }
 
-inline dmnsn_vector
+DMNSN_INLINE dmnsn_vector
 dmnsn_vector_div(dmnsn_vector lhs, dmnsn_scalar rhs)
 {
   return dmnsn_vector_construct(lhs.x/rhs, lhs.y/rhs, lhs.z/rhs);
 }
 
-inline dmnsn_scalar
+DMNSN_INLINE dmnsn_scalar
 dmnsn_vector_dot(dmnsn_vector lhs, dmnsn_vector rhs)
 {
   return lhs.x*rhs.x + lhs.y*rhs.y + lhs.z*rhs.z;
 }
 
-inline dmnsn_vector
+DMNSN_INLINE dmnsn_vector
 dmnsn_vector_cross(dmnsn_vector lhs, dmnsn_vector rhs)
 {
   return dmnsn_vector_construct(lhs.y*rhs.z - lhs.z*rhs.y,
@@ -83,7 +83,7 @@ typedef struct {
 } dmnsn_line;
 
 /* A point on a line, defined by x0 + t*n */
-inline dmnsn_vector
+DMNSN_INLINE dmnsn_vector
 dmnsn_line_point(dmnsn_line l, dmnsn_scalar t)
 {
   return dmnsn_vector_add(l.x0, dmnsn_vector_mul(t, l.n));
diff --git a/libdimension/inlines.c b/libdimension/inlines.c
new file mode 100644
index 0000000..51348fa
--- /dev/null
+++ b/libdimension/inlines.c
@@ -0,0 +1,22 @@
+/*************************************************************************
+ * 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/>.                                       *
+ *************************************************************************/
+
+#define DMNSN_INLINE
+#include "dimension.h"
diff --git a/tests/png.c b/tests/png.c
index e16ee8e..93cb266 100644
--- a/tests/png.c
+++ b/tests/png.c
@@ -6,6 +6,7 @@
 
 int main() {
   dmnsn_canvas *canvas;
+  dmnsn_sRGB sRGB;
   FILE *ofile, *ifile;
   unsigned int x, y;
 
@@ -15,37 +16,40 @@ int main() {
     return EXIT_FAILURE;
   }
 
-  ofile = fopen("dimension.png", "wb");
+  ofile = fopen("dimension1.png", "wb");
   if (!ofile) {
-    fprintf(stderr, "--- Opening 'dimension.png' for writing failed! ---\n");
+    fprintf(stderr, "--- Opening 'dimension1.png' for writing failed! ---\n");
     return EXIT_FAILURE;
   }
 
   for (x = 0; x < canvas->x; ++x) {
     for (y = 0; y < canvas->y; ++y) {
       if (x < canvas->x/3) {
-        canvas->pixels[y*canvas->x + x].r = UINT16_MAX;
-        canvas->pixels[y*canvas->x + x].g = 0;
-        canvas->pixels[y*canvas->x + x].b = 0;
+        sRGB.R = 1.0;
+        sRGB.G = 0.0;
+        sRGB.B = 0.0;
+        canvas->pixels[y*canvas->x + x] = dmnsn_color_from_sRGB(sRGB);
       } else if (x < 2*canvas->x/3) {
-        canvas->pixels[y*canvas->x + x].r = 0;
-        canvas->pixels[y*canvas->x + x].g = UINT16_MAX;
-        canvas->pixels[y*canvas->x + x].b = 0;
+        sRGB.R = 0.0;
+        sRGB.G = 1.0;
+        sRGB.B = 0.0;
+        canvas->pixels[y*canvas->x + x] = dmnsn_color_from_sRGB(sRGB);
       } else {
-        canvas->pixels[y*canvas->x + x].r = 0;
-        canvas->pixels[y*canvas->x + x].g = 0;
-        canvas->pixels[y*canvas->x + x].b = UINT16_MAX;
+        sRGB.R = 0.0;
+        sRGB.G = 0.0;
+        sRGB.B = 1.0;
+        canvas->pixels[y*canvas->x + x] = dmnsn_color_from_sRGB(sRGB);
       }
 
       if (y < canvas->y/3) {
-        canvas->pixels[y*canvas->x + x].a = 0;
-        canvas->pixels[y*canvas->x + x].t = 0;
+        canvas->pixels[y*canvas->x + x].filter = 0.0;
+        canvas->pixels[y*canvas->x + x].trans  = 0.0;
       } else if (y < 2*canvas->y/3) {
-        canvas->pixels[y*canvas->x + x].a = UINT16_MAX/4;
-        canvas->pixels[y*canvas->x + x].t = 0;
+        canvas->pixels[y*canvas->x + x].filter = 1.0/3.0;
+        canvas->pixels[y*canvas->x + x].trans  = 0.0;
       } else {
-        canvas->pixels[y*canvas->x + x].a = UINT16_MAX/4;
-        canvas->pixels[y*canvas->x + x].t = UINT16_MAX/2;
+        canvas->pixels[y*canvas->x + x].filter = 1.0/3.0;
+        canvas->pixels[y*canvas->x + x].trans  = 1.0/3.0;
       }
     }
   }
@@ -58,9 +62,9 @@ int main() {
   dmnsn_delete_canvas(canvas);
 
   fclose(ofile);
-  ifile = fopen("dimension.png", "rb");
+  ifile = fopen("dimension1.png", "rb");
   if (!ifile) {
-    fprintf(stderr, "--- Opening 'dimension.png' for reading failed! ---\n");
+    fprintf(stderr, "--- Opening 'dimension1.png' for reading failed! ---\n");
     return EXIT_FAILURE;
   }
 
@@ -70,9 +74,9 @@ int main() {
   }
 
   fclose(ifile);
-  ofile = fopen("dimension.png", "wb");
+  ofile = fopen("dimension2.png", "wb");
   if (!ofile) {
-    fprintf(stderr, "--- Opening 'dimension.png' for writing failed! ---\n");
+    fprintf(stderr, "--- Opening 'dimension2.png' for writing failed! ---\n");
     return EXIT_FAILURE;
   }