fix the RGB-linear metrics, and name the current one YUV

diff --git a/s2tc.cpp b/s2tc.cpp
index 90bb05c..d770927 100644 (file)
--- a/s2tc.cpp
+++ b/s2tc.cpp
@@ -518,7 +518,7 @@ inline int color_dist_avg(const color_t &a, const color_t &b)
        return ((dr*dr) << 2) + dg*dg + ((db*db) << 2);
 }
 
-inline int color_dist_rgb(const color_t &a, const color_t &b)
+inline int color_dist_yuv(const color_t &a, const color_t &b)
 {
        int dr = a.r - b.r; // multiplier: 31 (-1..1)
        int dg = a.g - b.g; // multiplier: 63 (-1..1)
@@ -529,14 +529,25 @@ inline int color_dist_rgb(const color_t &a, const color_t &b)
        return ((y*y) << 1) + SHRR(u*u, 3) + SHRR(v*v, 5);
 }
 
+inline int color_dist_rgb(const color_t &a, const color_t &b)
+{
+       int dr = a.r - b.r; // multiplier: 31 (-1..1)
+       int dg = a.g - b.g; // multiplier: 63 (-1..1)
+       int db = a.b - b.b; // multiplier: 31 (-1..1)
+       int y = dr * 21*2 + dg * 72 + db * 7*2; // multiplier: 6272
+       int u = dr * 202 - y; // * 0.5 / (1 - 0.21)
+       int v = db * 202 - y; // * 0.5 / (1 - 0.07)
+       return ((y*y) << 1) + SHRR(u*u, 3) + SHRR(v*v, 5);
+}
+
 inline int color_dist_srgb(const color_t &a, const color_t &b)
 {
        int dr = a.r * (int) a.r - b.r * (int) b.r; // multiplier: 31*31
        int dg = a.g * (int) a.g - b.g * (int) b.g; // multiplier: 63*63
        int db = a.b * (int) a.b - b.b * (int) b.b; // multiplier: 31*31
-       int y = dr * 30*2*2 + dg * 59 + db * 11*2*2; // multiplier: 391775
-       int u = dr * 408 - y; // * 0.5 / (1 - 0.30)
-       int v = db * 408 - y; // * 0.5 / (1 - 0.11)
+       int y = dr * 21*2*2 + dg * 72 + db * 7*2*2; // multiplier: 393400
+       int u = dr * 409 - y; // * 0.5 / (1 - 0.30)
+       int v = db * 409 - y; // * 0.5 / (1 - 0.11)
        int sy = SHRR(y, 3) * SHRR(y, 4);
        int su = SHRR(u, 3) * SHRR(u, 4);
        int sv = SHRR(v, 3) * SHRR(v, 4);
@@ -725,6 +736,7 @@ enum DxtMode
 enum ColorDistMode
 {
        RGB,
+       YUV,
        SRGB,
        AVG,
        NORMALMAP
@@ -922,6 +934,9 @@ void s2tc_encode_block(unsigned char *out, const unsigned char *rgba, int iw, in
                case RGB:
                        s2tc_encode_block<color_dist_rgb>(out, rgba, iw, w, h, dxt, nrandom);
                        break;
+               case YUV:
+                       s2tc_encode_block<color_dist_yuv>(out, rgba, iw, w, h, dxt, nrandom);
+                       break;
                case SRGB:
                        s2tc_encode_block<color_dist_srgb>(out, rgba, iw, w, h, dxt, nrandom);
                        break;
@@ -957,7 +972,7 @@ int usage(const char *me)
                        "    [-o outfile.dds]\n"
                        "    [-t {DXT1|DXT3|DXT5}]\n"
                        "    [-r randomcount]\n"
-                       "    [-c {RGB|SRGB|AVG|NORMALMAP}]\n",
+                       "    [-c {RGB|YUV|SRGB|AVG|NORMALMAP}]\n",
                        me);
        return 1;
 }
@@ -1002,6 +1017,8 @@ int main(int argc, char **argv)
                        case 'c':
                                if(!strcasecmp(optarg, "RGB"))
                                        cd = RGB;
+                               else if(!strcasecmp(optarg, "YUV"))
+                                       cd = YUV;
                                else if(!strcasecmp(optarg, "SRGB"))
                                        cd = SRGB;
                                else if(!strcasecmp(optarg, "AVG"))