support "proper" refining

diff --git a/s2tc_compressor.cpp b/s2tc_compressor.cpp
index 3911b9d..d2884a2 100644 (file)
--- a/s2tc_compressor.cpp
+++ b/s2tc_compressor.cpp
@@ -99,7 +99,7 @@ namespace
                // find luminance
                int y = 37 * (r * 21*2*2 + g * 72 + b * 7*2*2); // multiplier: 14555800
                // square root it (!)
-               y = sqrt(y); // now in range 0 to 3815
+               y = sqrtf(y) + 0.5f; // now in range 0 to 3815
                return y;
        }
 
@@ -307,6 +307,40 @@ namespace
                MODE_FAST
        };
 
+       template<ColorDistFunc ColorDist> inline int refine_component_encode(int comp)
+       {
+               return comp;
+       }
+       template<> inline int refine_component_encode<color_dist_srgb>(int comp)
+       {
+               return comp * comp;
+       }
+       template<> inline int refine_component_encode<color_dist_srgb_mixed>(int comp)
+       {
+               return comp * comp;
+       }
+       template<> inline int refine_component_encode<color_dist_lab_srgb>(int comp)
+       {
+               return comp * comp;
+       }
+
+       template<ColorDistFunc ColorDist> inline int refine_component_decode(int comp)
+       {
+               return comp;
+       }
+       template<> inline int refine_component_decode<color_dist_srgb>(int comp)
+       {
+               return sqrtf(comp) + 0.5f;
+       }
+       template<> inline int refine_component_decode<color_dist_srgb_mixed>(int comp)
+       {
+               return sqrtf(comp) + 0.5f;
+       }
+       template<> inline int refine_component_decode<color_dist_lab_srgb>(int comp)
+       {
+               return sqrtf(comp) + 0.5f;
+       }
+
        template<DxtMode dxt, ColorDistFunc ColorDist, CompressionMode mode, bool refine>
        inline void s2tc_encode_block(unsigned char *out, const unsigned char *rgba, int iw, int w, int h, int nrandom)
        {
@@ -499,9 +533,9 @@ namespace
                                                        if(refine)
                                                        {
                                                                ++nc1;
-                                                               sc1r += c[2].r;
-                                                               sc1g += c[2].g;
-                                                               sc1b += c[2].b;
+                                                               sc1r += refine_component_encode<ColorDist>(c[2].r);
+                                                               sc1g += refine_component_encode<ColorDist>(c[2].g);
+                                                               sc1b += refine_component_encode<ColorDist>(c[2].b);
                                                        }
                                                }
                                                else
@@ -509,9 +543,9 @@ namespace
                                                        if(refine)
                                                        {
                                                                ++nc0;
-                                                               sc0r += c[2].r;
-                                                               sc0g += c[2].g;
-                                                               sc0b += c[2].b;
+                                                               sc0r += refine_component_encode<ColorDist>(c[2].r);
+                                                               sc0g += refine_component_encode<ColorDist>(c[2].g);
+                                                               sc0b += refine_component_encode<ColorDist>(c[2].b);
                                                        }
                                                }
                                                break;
@@ -527,9 +561,9 @@ namespace
                                                        if(refine)
                                                        {
                                                                ++nc1;
-                                                               sc1r += c[2].r;
-                                                               sc1g += c[2].g;
-                                                               sc1b += c[2].b;
+                                                               sc1r += refine_component_encode<ColorDist>(c[2].r);
+                                                               sc1g += refine_component_encode<ColorDist>(c[2].g);
+                                                               sc1b += refine_component_encode<ColorDist>(c[2].b);
                                                        }
                                                }
                                                else
@@ -537,9 +571,9 @@ namespace
                                                        if(refine)
                                                        {
                                                                ++nc0;
-                                                               sc0r += c[2].r;
-                                                               sc0g += c[2].g;
-                                                               sc0b += c[2].b;
+                                                               sc0r += refine_component_encode<ColorDist>(c[2].r);
+                                                               sc0g += refine_component_encode<ColorDist>(c[2].g);
+                                                               sc0b += refine_component_encode<ColorDist>(c[2].b);
                                                        }
                                                }
                                                break;
@@ -554,9 +588,9 @@ namespace
                                                                if(refine)
                                                                {
                                                                        ++nc1;
-                                                                       sc1r += c[2].r;
-                                                                       sc1g += c[2].g;
-                                                                       sc1b += c[2].b;
+                                                                       sc1r += refine_component_encode<ColorDist>(c[2].r);
+                                                                       sc1g += refine_component_encode<ColorDist>(c[2].g);
+                                                                       sc1b += refine_component_encode<ColorDist>(c[2].b);
                                                                }
                                                        }
                                                        else
@@ -564,9 +598,9 @@ namespace
                                                                if(refine)
                                                                {
                                                                        ++nc0;
-                                                                       sc0r += c[2].r;
-                                                                       sc0g += c[2].g;
-                                                                       sc0b += c[2].b;
+                                                                       sc0r += refine_component_encode<ColorDist>(c[2].r);
+                                                                       sc0g += refine_component_encode<ColorDist>(c[2].g);
+                                                                       sc0b += refine_component_encode<ColorDist>(c[2].b);
                                                                }
                                                        }
                                                }
@@ -584,15 +618,15 @@ namespace
                        }
                        if(nc0)
                        {
-                               c[0].r = (2 * sc0r + nc0) / (2 * nc0);
-                               c[0].g = (2 * sc0g + nc0) / (2 * nc0);
-                               c[0].b = (2 * sc0b + nc0) / (2 * nc0);
+                               c[0].r = refine_component_decode<ColorDist>((2 * sc0r + nc0) / (2 * nc0));
+                               c[0].g = refine_component_decode<ColorDist>((2 * sc0g + nc0) / (2 * nc0));
+                               c[0].b = refine_component_decode<ColorDist>((2 * sc0b + nc0) / (2 * nc0));
                        }
                        if(nc1)
                        {
-                               c[1].r = (2 * sc1r + nc1) / (2 * nc1);
-                               c[1].g = (2 * sc1g + nc1) / (2 * nc1);
-                               c[1].b = (2 * sc1b + nc1) / (2 * nc1);
+                               c[1].r = refine_component_decode<ColorDist>((2 * sc1r + nc1) / (2 * nc1));
+                               c[1].g = refine_component_decode<ColorDist>((2 * sc1g + nc1) / (2 * nc1));
+                               c[1].b = refine_component_decode<ColorDist>((2 * sc1b + nc1) / (2 * nc1));
                        }
 
                        if(dxt == DXT5)