uniform color quantization (#1868)

* rename I_GetPaletteIndex->I_GetNearestColor

src/am_map.c

@@ -2369,8 +2369,8 @@ void AM_ColorPreset(void)
   if (mapcolor_preset == AM_PRESET_CRISPY)
   {
     byte *playpal = W_CacheLumpName("PLAYPAL", PU_CACHE);
-    mapcolor_secr = I_GetPaletteIndex(playpal, 255, 0, 255);
-    mapcolor_revsecr = I_GetPaletteIndex(playpal, 119, 255, 111);
+    mapcolor_secr = I_GetNearestColor(playpal, 255, 0, 255);
+    mapcolor_revsecr = I_GetNearestColor(playpal, 119, 255, 111);
   }
 }
 

src/i_video.c

@@ -1025,7 +1025,7 @@ void I_SetPalette(byte *palette)
 
 // Taken from Chocolate Doom chocolate-doom/src/i_video.c:L841-867
 
-byte I_GetPaletteIndex(byte *palette, int r, int g, int b)
+byte I_GetNearestColor(byte *palette, int r, int g, int b)
 {
     byte best;
     int best_diff, diff;

src/i_video.h

@@ -82,7 +82,7 @@ extern boolean correct_aspect_ratio;
 extern boolean screenvisible;
 
 extern int gamma2;
-byte I_GetPaletteIndex(byte *palette, int r, int g, int b);
+byte I_GetNearestColor(byte *palette, int r, int g, int b);
 
 boolean I_WritePNGfile(char *filename); // [FG] screenshots in PNG format
 

src/mn_font.c

@@ -111,7 +111,7 @@ boolean MN_LoadFon2(const byte *gfx_data, int size)
         int r = *p++;
         int g = *p++;
         int b = *p++;
-        translate[i] = I_GetPaletteIndex(playpal, r, g, b);
+        translate[i] = I_GetNearestColor(playpal, r, g, b);
     }
 
     // 0 is transparent, last is border color

src/r_sky.c

@@ -111,7 +111,7 @@ static byte R_SkyBlendColor(int tex)
   b = colors[width/3].b;
   Z_Free(colors);
 
-  return I_GetPaletteIndex(pal, r, g, b);
+  return I_GetNearestColor(pal, r, g, b);
 }
 
 typedef struct skycolor_s

src/st_stuff.c

@@ -370,7 +370,7 @@ static void ST_DrawSolidBackground(int st_x)
     b /= 2 * depth * (v1 - v0);
 
     // [FG] tune down to half saturation (for empiric reasons)
-    col = I_GetPaletteIndex(pal, r/2, g/2, b/2);
+    col = I_GetNearestColor(pal, r/2, g/2, b/2);
 
     V_FillRect(0, v0, video.unscaledw, v1 - v0, col);
   }

src/v_flextran.c

@@ -71,7 +71,7 @@ void V_InitFlexTranTable(void)
         {
             for (b = 0; b < 32; ++b)
             {
-                RGB32k[r][g][b] = I_GetPaletteIndex(palette, MAKECOLOR(r),
+                RGB32k[r][g][b] = I_GetNearestColor(palette, MAKECOLOR(r),
                                                     MAKECOLOR(g), MAKECOLOR(b));
             }
         }

src/v_fmt.c

@@ -268,6 +268,82 @@ static void *DummyFlat(int lump, pu_tag tag)
     return lumpcache[lump];
 }
 
+// Uniform Color Quantization
+//
+// Each color component axis (red, green and blue) is divided into a few fixed
+// segments (8-8-4 in 256 colors). Each found color is placed into a
+// corresponding segment slot. After all the colors are added, an average
+// color is calculated for each slot. Those are the colors of the palette.
+
+typedef struct
+{
+    int value;
+    int pixel_count;
+} color_slot_t;
+
+static void AddValue(color_slot_t *s, int component)
+{
+    s->value += component;
+    s->pixel_count++;
+}
+
+static int GetAverage(color_slot_t *s)
+{
+    int result = 0;
+
+    if (s->pixel_count > 0)
+    {
+        result = (s->pixel_count == 1) ? s->value : (s->value / s->pixel_count);
+    }
+
+    return result;
+}
+
+typedef struct
+{
+    color_slot_t red_slots[8];
+    color_slot_t green_slots[8];
+    color_slot_t blue_slots[4];
+
+    byte palette[768];
+} uniform_quantizer_t;
+
+static void AddColor(uniform_quantizer_t *q, int r, int g, int b)
+{
+    int red_index = r >> 5;
+    int green_index = g >> 5;
+    int blue_index = b >> 6;
+    AddValue(&q->red_slots[red_index], r);
+    AddValue(&q->green_slots[green_index], g);
+    AddValue(&q->blue_slots[blue_index], b);
+}
+
+static void GetPalette(uniform_quantizer_t *q)
+{
+    byte *roller = q->palette;
+
+    for (int rs = 0; rs < arrlen(q->red_slots); ++rs)
+    {
+        for (int gs = 0; gs < arrlen(q->green_slots); ++gs)
+        {
+            for (int bs = 0; bs < arrlen(q->blue_slots); ++bs)
+            {
+                *roller++ = GetAverage(&q->red_slots[rs]);
+                *roller++ = GetAverage(&q->green_slots[gs]);
+                *roller++ = GetAverage(&q->blue_slots[bs]);
+            }
+        }
+    }
+}
+
+static int GetPaletteIndex(int r, int g, int b)
+{
+    int red_index = r >> 5;
+    int green_index = g >> 5;
+    int blue_index = b >> 6;
+    return (red_index << 5) + (green_index << 2) + blue_index;
+}
+
 typedef struct
 {
     spng_ctx *ctx;
@@ -340,8 +416,7 @@ static boolean DecodePNG(png_t *png)
 
     if (ret)
     {
-        I_Printf(VB_ERROR, "DecodeImage: spng_get_ihdr %s\n",
-                 spng_strerror(ret));
+        I_Printf(VB_ERROR, "DecodePNG: spng_get_ihdr %s\n", spng_strerror(ret));
         return false;
     }
 
@@ -368,7 +443,7 @@ static boolean DecodePNG(png_t *png)
 
     if (ret)
     {
-        I_Printf(VB_ERROR, "DecodeImage: spng_decoded_image_size %s",
+        I_Printf(VB_ERROR, "DecodePNG: spng_decoded_image_size %s",
                  spng_strerror(ret));
         return false;
     }
@@ -378,7 +453,7 @@ static boolean DecodePNG(png_t *png)
 
     if (ret)
     {
-        I_Printf(VB_ERROR, "DecodeImage: spng_decode_image %s",
+        I_Printf(VB_ERROR, "DecodePNG: spng_decode_image %s",
                  spng_strerror(ret));
         free(image);
         return false;
@@ -391,6 +466,8 @@ static boolean DecodePNG(png_t *png)
         int indexed_size = image_size / 3;
         byte *indexed_image = malloc(indexed_size);
 
+        uniform_quantizer_t q = {0};
+
         byte *roller = image;
 
         for (int i = 0; i < indexed_size; ++i)
@@ -399,7 +476,31 @@ static boolean DecodePNG(png_t *png)
             int g = *roller++;
             int b = *roller++;
 
-            indexed_image[i] = I_GetPaletteIndex(playpal, r, g, b);
+            AddColor(&q, r, g, b);
+        }
+
+        GetPalette(&q);
+
+        byte translate[256];
+        byte *palette = q.palette;
+        for (int i = 0; i < 256; ++i)
+        {
+            int r = *palette++;
+            int g = *palette++;
+            int b = *palette++;
+
+            translate[i] = I_GetNearestColor(playpal, r, g, b);
+        }
+
+        roller = image;
+
+        for (int i = 0; i < indexed_size; ++i)
+        {
+            int r = *roller++;
+            int g = *roller++;
+            int b = *roller++;
+
+            indexed_image[i] = translate[GetPaletteIndex(r, g, b)];
         }
 
         free(image);
@@ -412,6 +513,8 @@ static boolean DecodePNG(png_t *png)
         int indexed_size = image_size / 4;
         byte *indexed_image = malloc(indexed_size);
 
+        uniform_quantizer_t q = {0};
+
         byte *roller = image;
 
         byte used_colors[256] = {0};
@@ -423,22 +526,34 @@ static boolean DecodePNG(png_t *png)
             int g = *roller++;
             int b = *roller++;
             int a = *roller++;
-
             if (a < 255)
             {
                 has_alpha = true;
                 continue;
             }
 
-            byte c = I_GetPaletteIndex(playpal, r, g, b);
-            used_colors[c] = 1;
-            indexed_image[i] = c;
+            AddColor(&q, r, g, b);
         }
 
+        GetPalette(&q);
+
+        byte translate[256];
+        byte *palette = q.palette;
+        for (int i = 0; i < 256; ++i)
+        {
+            int r = *palette++;
+            int g = *palette++;
+            int b = *palette++;
+
+            byte c = I_GetNearestColor(playpal, r, g, b);
+            used_colors[c] = 1;
+            translate[i] = c;
+        }
+
+        int color_key = NO_COLOR_KEY;
+
         if (has_alpha)
         {
-            int color_key = NO_COLOR_KEY;
-
             for (int i = 0; i < 256; ++i)
             {
                 if (used_colors[i] == 0)
@@ -447,20 +562,24 @@ static boolean DecodePNG(png_t *png)
                     break;
                 }
             }
+            png->color_key = color_key;
+        }
 
-            if (color_key != NO_COLOR_KEY)
+        roller = image;
+
+        for (int i = 0; i < indexed_size; ++i)
+        {
+            int r = *roller++;
+            int g = *roller++;
+            int b = *roller++;
+            int a = *roller++;
+            if (a < 255)
             {
-                roller = image;
-                for (int i = 0; i < indexed_size; ++i)
-                {
-                    roller += 3;
-                    if (*roller++ < 255)
-                    {
-                        indexed_image[i] = color_key;
-                    }
-                }
-                png->color_key = color_key;
+                indexed_image[i] = color_key;
+                continue;
             }
+
+            indexed_image[i] = translate[GetPaletteIndex(r, g, b)];
         }
 
         free(image);
@@ -475,7 +594,7 @@ static boolean DecodePNG(png_t *png)
 
         if (ret)
         {
-            I_Printf(VB_ERROR, "DecodeImage: spng_get_plte %s\n",
+            I_Printf(VB_ERROR, "DecodePNG: spng_get_plte %s\n",
                      spng_strerror(ret));
             return false;
         }
@@ -500,7 +619,7 @@ static boolean DecodePNG(png_t *png)
 
             need_translation = true;
             translate[i] =
-                I_GetPaletteIndex(playpal, e->red, e->green, e->blue);
+                I_GetNearestColor(playpal, e->red, e->green, e->blue);
         }
 
         if (need_translation)

src/v_trans.c

@@ -285,5 +285,5 @@ byte V_Colorize(byte *playpal, int cr, byte source)
     rgb.y *= 255.0;
     rgb.z *= 255.0;
 
-    return I_GetPaletteIndex(playpal, (int)rgb.x, (int)rgb.y, (int)rgb.z);
+    return I_GetNearestColor(playpal, (int)rgb.x, (int)rgb.y, (int)rgb.z);
 }

src/v_video.c

@@ -200,8 +200,8 @@ void V_InitColorTranslation(void)
         cr_bright[i] = V_Colorize(playpal, CR_BRIGHT, (byte)i);
     }
 
-    v_lightest_color = I_GetPaletteIndex(playpal, 0xFF, 0xFF, 0xFF);
-    v_darkest_color  = I_GetPaletteIndex(playpal, 0x00, 0x00, 0x00);
+    v_lightest_color = I_GetNearestColor(playpal, 0xFF, 0xFF, 0xFF);
+    v_darkest_color  = I_GetNearestColor(playpal, 0x00, 0x00, 0x00);
 
     byte *palsrc = playpal;
     for (int i = 0; i < 256; ++i)
@@ -213,7 +213,7 @@ void V_InitColorTranslation(void)
         // formula is taken from dcolors.c preseving "Carmack's typo"
         // https://doomwiki.org/wiki/Carmack%27s_typo
         int gray = (red * 0.299 + green * 0.587 + blue * 0.144) * 255;
-        invul_gray[i] = I_GetPaletteIndex(playpal, gray, gray, gray);
+        invul_gray[i] = I_GetNearestColor(playpal, gray, gray, gray);
     }
 }