tga optimizations

stb_image.c

@@ -22,7 +22,7 @@
       - overridable dequantizing-IDCT, YCbCr-to-RGB conversion (define STBI_SIMD)
 
    Latest revisions:
-      1.35 (2014-05-27) warnings, bugfixes, etc
+      1.35 (2014-05-27) warnings, bugfixes, TGA optimization, etc
       1.34 (unknown   ) warning fix
       1.33 (2011-07-14) minor fixes suggested by Dave Moore
       1.32 (2011-07-13) info support for all filetypes (SpartanJ)
@@ -57,7 +57,7 @@
                                                  John Bartholomew
  Optimizations & bugfixes                        Ken Hamada
     Fabian "ryg" Giesen                          Cort Stratton
-                                                 Blazej Dariusz Roszkowski
+    Arseny Kapoulkine                            Blazej Dariusz Roszkowski
                                                  Thibault Reuille
  If your name should be here but                 Paul Du Bois
  isn't let Sean know.                            Guillaume George
@@ -3260,13 +3260,13 @@ static stbi_uc *tga_load(stbi *s, int *x, int *y, int *comp, int req_comp)
    int tga_width = get16le(s);
    int tga_height = get16le(s);
    int tga_bits_per_pixel = get8u(s);
+   int tga_comp = tga_bits_per_pixel / 8;
    int tga_inverted = get8u(s);
    //   image data
    unsigned char *tga_data;
    unsigned char *tga_palette = NULL;
    int i, j;
    unsigned char raw_data[4];
-   unsigned char trans_data[4];
    int RLE_count = 0;
    int RLE_repeating = 0;
    int read_next_pixel = 1;
@@ -3294,29 +3294,29 @@ static stbi_uc *tga_load(stbi *s, int *x, int *y, int *comp, int req_comp)
    //   If I'm paletted, then I'll use the number of bits from the palette
    if ( tga_indexed )
    {
-      tga_bits_per_pixel = tga_palette_bits;
+      tga_comp = tga_palette_bits / 8;
    }
 
    //   tga info
    *x = tga_width;
    *y = tga_height;
-   if ( (req_comp < 1) || (req_comp > 4) )
+   if (comp) *comp = tga_comp;
-   {
+
-      //   just use whatever the file was
-      req_comp = tga_bits_per_pixel / 8;
-      *comp = req_comp;
-   } else
-   {
-      //   force a new number of components
-      *comp = tga_bits_per_pixel/8;
-   }
    tga_data = (unsigned char*)malloc( tga_width * tga_height * req_comp );
    if (!tga_data) return epuc("outofmem", "Out of memory");
 
    //   skip to the data's starting position (offset usually = 0)
    skip(s, tga_offset );
+
+   if ( !tga_indexed && !tga_is_RLE) {
+      for (i=0; i < tga_height; ++i) {
+         int y = tga_inverted ? tga_height -i - 1 : i;
+         stbi__uint8 *tga_row = tga_data + y*tga_width*tga_comp;
+         getn(s, tga_row, tga_width * tga_comp);
+      }
+   } else  {
       //   do I need to load a palette?
-   if ( tga_indexed )
+      if ( tga_indexed)
       {
          //   any data to skip? (offset usually = 0)
          skip(s, tga_palette_start );
@@ -3333,7 +3333,6 @@ static stbi_uc *tga_load(stbi *s, int *x, int *y, int *comp, int req_comp)
          }
       }
       //   load the data
-   trans_data[0] = trans_data[1] = trans_data[2] = trans_data[3] = 0;
       for (i=0; i < tga_width * tga_height; ++i)
       {
          //   if I'm in RLE mode, do I need to get a RLE chunk?
@@ -3380,67 +3379,14 @@ static stbi_uc *tga_load(stbi *s, int *x, int *y, int *comp, int req_comp)
                   raw_data[j] = get8u(s);
                }
             }
-         //   convert raw to the intermediate format
-         switch (tga_bits_per_pixel)
-         {
-         case 8:
-            //   Luminous => RGBA
-            trans_data[0] = raw_data[0];
-            trans_data[1] = raw_data[0];
-            trans_data[2] = raw_data[0];
-            trans_data[3] = 255;
-            break;
-         case 16:
-            //   Luminous,Alpha => RGBA
-            trans_data[0] = raw_data[0];
-            trans_data[1] = raw_data[0];
-            trans_data[2] = raw_data[0];
-            trans_data[3] = raw_data[1];
-            break;
-         case 24:
-            //   BGR => RGBA
-            trans_data[0] = raw_data[2];
-            trans_data[1] = raw_data[1];
-            trans_data[2] = raw_data[0];
-            trans_data[3] = 255;
-            break;
-         case 32:
-            //   BGRA => RGBA
-            trans_data[0] = raw_data[2];
-            trans_data[1] = raw_data[1];
-            trans_data[2] = raw_data[0];
-            trans_data[3] = raw_data[3];
-            break;
-         }
             //   clear the reading flag for the next pixel
             read_next_pixel = 0;
          } // end of reading a pixel
-      //   convert to final format
+
-      switch (req_comp)
+         // copy data
-      {
+         for (j = 0; j < tga_comp; ++j)
-      case 1:
+           tga_data[i*tga_comp+j] = raw_data[j];
-         //   RGBA => Luminance
+
-         tga_data[i*req_comp+0] = compute_y(trans_data[0],trans_data[1],trans_data[2]);
-         break;
-      case 2:
-         //   RGBA => Luminance,Alpha
-         tga_data[i*req_comp+0] = compute_y(trans_data[0],trans_data[1],trans_data[2]);
-         tga_data[i*req_comp+1] = trans_data[3];
-         break;
-      case 3:
-         //   RGBA => RGB
-         tga_data[i*req_comp+0] = trans_data[0];
-         tga_data[i*req_comp+1] = trans_data[1];
-         tga_data[i*req_comp+2] = trans_data[2];
-         break;
-      case 4:
-         //   RGBA => RGBA
-         tga_data[i*req_comp+0] = trans_data[0];
-         tga_data[i*req_comp+1] = trans_data[1];
-         tga_data[i*req_comp+2] = trans_data[2];
-         tga_data[i*req_comp+3] = trans_data[3];
-         break;
-      }
          //   in case we're in RLE mode, keep counting down
          --RLE_count;
       }
@@ -3466,6 +3412,25 @@ static stbi_uc *tga_load(stbi *s, int *x, int *y, int *comp, int req_comp)
       {
          free( tga_palette );
       }
+   }
+
+   // swap RGB
+   if (tga_comp >= 3)
+   {
+      unsigned char* tga_pixel = tga_data;
+      for (i=0; i < tga_width * tga_height; ++i)
+      {
+         unsigned char temp = tga_pixel[0];
+         tga_pixel[0] = tga_pixel[2];
+         tga_pixel[2] = temp;
+         tga_pixel += tga_comp;
+      }
+   }
+
+   // convert to target component count
+   if (req_comp && req_comp != tga_comp)
+      tga_data = convert_format(tga_data, tga_comp, req_comp, tga_width, tga_height);
+
    //   the things I do to get rid of an error message, and yet keep
    //   Microsoft's C compilers happy... [8^(
    tga_palette_start = tga_palette_len = tga_palette_bits =
@@ -4624,6 +4589,7 @@ int stbi_info_from_callbacks(stbi_io_callbacks const *c, void *user, int *x, int
              fix broken STBI_SIMD path
              fix bug where stbi_load_from_file no longer left file pointer in correct place
              fix broken non-easy path for 32-bit BMP (possibly never used)
+             TGA optimization by Arseny Kapoulkine
       1.34 (unknown)
              use STBI_NOTUSED in resample_row_generic(), fix one more leak in tga failure case
       1.33 (2011-07-14)