Changeset 2271 for trunkTweet

Timestamp:

Jan 24, 2013, 12:26:16 AM (7 years ago)

Author:

sam

Message:

color: tweak RGB to HSV/HSL code for not yet investigated numerical
stability issues.

File:

• trunk/src/lol/image/color.h (modified) (4 diffs)

trunk/src/lol/image/color.h

@@ -89 +89 @@
         float K = 0.f;
 
-        if (src.g < src.b)
+        if (src.b - src.g > 1e-20f)
             src = src.rbg, K = -1.f;
 
-        if (src.r < src.g)
+        if (src.g - src.r > 1e-20f)
             src = src.grb, K = -2.f / 6.f - K;
 
@@ -113 +113 @@
         float K = 0.f;
 
-        if (src.g < src.b)
+        /* FIXME: this appears to be needed for numerical stability on
+         * i386 hardware using -ffast-math. Otherwise if (src.g < src.b)
+         * would suffice. */
+        if (src.b - src.g > 1e-20f)
             src = src.rbg, K = -1.f;
 
-        if (src.r < src.g)
+        if (src.g - src.r > 1e-20f)
             src = src.grb, K = -2.f / 6.f - K;
 
@@ -137 +140 @@
     {
         float tmp = (2 - src.y) * src.z;
-        return vec3(src.x, src.y * src.z / (1.f - abs(1.f - tmp)), 0.5f * tmp);
+        return vec3(src.x,
+                    src.y * src.z / (min(tmp, 2.f - tmp) + 1e-20f),
+                    0.5f * tmp);
     }
 
@@ -151 +156 @@
     {
         float tmp = src.y * (0.5f - abs(0.5f - src.z));
-        return vec3(src.x, 2.f * tmp / (src.z + tmp), src.z + tmp);
+        return vec3(src.x, 2.f * tmp / (src.z + tmp + 1e-20f), src.z + tmp);
     }