From 5eab850f84d30bfe2042b439c65b7e83db581348 Mon Sep 17 00:00:00 2001
From: Tavian Barnes <tavianator@gmail.com>
Date: Mon, 9 Nov 2009 14:07:14 -0500
Subject: Rudimentary light/shadow handling.

---
 libdimension/color.c | 56 +++++++++++++++++++++++++++++++++++++++++++---------
 1 file changed, 47 insertions(+), 9 deletions(-)

(limited to 'libdimension/color.c')

diff --git a/libdimension/color.c b/libdimension/color.c
index 7fb73ed..374a0a0 100644
--- a/libdimension/color.c
+++ b/libdimension/color.c
@@ -263,17 +263,14 @@ dmnsn_sRGB_from_color(dmnsn_color color)
 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, dmnsn_whitepoint);
-  Lab2 = dmnsn_Lab_from_color(color2, dmnsn_whitepoint);
+  dmnsn_CIE_Lab Lab1 = dmnsn_Lab_from_color(color1, dmnsn_whitepoint);
+  dmnsn_CIE_Lab Lab2 = dmnsn_Lab_from_color(color2, dmnsn_whitepoint);
 
-  Lab.L = Lab1.L + Lab2.L;
-  Lab.a = Lab1.a + Lab2.a;
-  Lab.b = Lab1.b + Lab2.b;
+  dmnsn_CIE_Lab Lab = { .L = Lab1.L + Lab2.L,
+                        .a = Lab1.a + Lab2.a,
+                        .b = Lab1.b + Lab2.b };
 
-  ret = dmnsn_color_from_Lab(Lab, dmnsn_whitepoint);
+  dmnsn_color ret = dmnsn_color_from_Lab(Lab, dmnsn_whitepoint);
   /* Weighted average of transparencies by intensity */
   ret.filter = (Lab1.L*color1.filter + Lab2.L*color2.filter)/Lab.L;
   ret.trans  = (Lab1.L*color1.trans  + Lab2.L*color2.trans)/Lab.L;
@@ -281,6 +278,47 @@ dmnsn_color_add(dmnsn_color color1, dmnsn_color color2)
   return ret;
 }
 
+/* Multiply a color by a scalar */
+dmnsn_color
+dmnsn_color_mul(double n, dmnsn_color color)
+{
+  dmnsn_CIE_Lab Lab = dmnsn_Lab_from_color(color, dmnsn_whitepoint);
+  double LabL = Lab.L;
+  Lab.L *= n;
+  Lab.a *= n;
+  Lab.b *= n;
+
+  dmnsn_color ret = dmnsn_color_from_Lab(Lab, dmnsn_whitepoint);
+  ret.filter = color.filter;
+  ret.trans  = color.trans;
+
+  return ret;
+}
+
+/* Illuminates `color' with `light' */
+dmnsn_color
+dmnsn_color_illuminate(dmnsn_color light, dmnsn_color color)
+{
+  dmnsn_CIE_Lab Lab1 = dmnsn_Lab_from_color(light, dmnsn_whitepoint);
+  dmnsn_CIE_Lab Lab2 = dmnsn_Lab_from_color(color, dmnsn_whitepoint);
+
+  double dot  = Lab1.L*Lab2.L + Lab1.a*Lab2.a + Lab1.b*Lab2.b;
+  double norm = sqrt(Lab2.L*Lab2.L + Lab2.a*Lab2.a + Lab2.b*Lab2.b);
+
+  if (norm == 0.0)
+    return dmnsn_black;
+
+  dmnsn_CIE_Lab Lab = { .L = dot*Lab2.L/norm/100.0,
+                        .a = dot*Lab2.a/norm,
+                        .b = dot*Lab2.b/norm };
+
+  dmnsn_color ret = dmnsn_color_from_Lab(Lab, dmnsn_whitepoint);
+  ret.filter = color.filter;
+  ret.trans  = color.trans;
+
+  return ret;
+}
+
 /* Find the perceptual difference between two colors, using CIE L*a*b*. */
 double
 dmnsn_color_difference(dmnsn_color color1, dmnsn_color color2)
-- 
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