GIFs2PNG algorithm: treat out-of-mask area as white pixels

Wohlstand · Jun 13, 2020 · 0d940806879c876e74ecf63b1dd83f874b096a78 · 0d94080
1 parent 5243baf
commit 0d940806879c876e74ecf63b1dd83f874b096a78
Showing 1 changed file with 22 additions and 5 deletions.
diff --git a/lib/Graphics/graphics_funcs.cpp b/lib/Graphics/graphics_funcs.cpp
@@ -287,15 +287,20 @@ void GraphicsHelps::mergeWithMask(FIBITMAP *image, FIBITMAP *mask)
     BYTE *FPixP = img_bits;
     BYTE *SPixP = mask_bits;
     RGBQUAD Npix = {0x00, 0x00, 0x00, 0xFF};   //Destination pixel color
+    BYTE Wpix[] = {0xFF, 0xFF, 0xFF, 0xFF};   //Dummy white pixel
     unsigned short newAlpha = 0xFF; //Calculated destination alpha-value
 
+    bool endOfY = false;
     unsigned int ym = mask_h - 1;
     unsigned int y = img_h - 1;
+
     while(1)
     {
         FPixP = img_bits + (img_w * y * 4);
-        SPixP = mask_bits + (mask_w * ym * 4);
-        for(unsigned int x = 0; (x < img_w) && (x < mask_w); x++)
+        if(!endOfY)
+            SPixP = mask_bits + (mask_w * ym * 4);
+
+        for(unsigned int x = 0; (x < img_w); x++)
         {
             Npix.rgbBlue = ((SPixP[FI_RGBA_BLUE] & 0x7F) | FPixP[FI_RGBA_BLUE]);
             Npix.rgbGreen = ((SPixP[FI_RGBA_GREEN] & 0x7F) | FPixP[FI_RGBA_GREEN]);
@@ -320,12 +325,24 @@ void GraphicsHelps::mergeWithMask(FIBITMAP *image, FIBITMAP *mask)
             FPixP[FI_RGBA_RED]   = Npix.rgbRed;
             FPixP[FI_RGBA_ALPHA] = static_cast<BYTE>(newAlpha);
             FPixP += 4;
-            SPixP += 4;
+
+            if(x >= mask_w - 1)
+                SPixP = Wpix;
+            else
+                SPixP += 4;
+        }
+
+        if(ym == 0)
+        {
+            endOfY = true;
+            SPixP = Wpix;
         }
+        else
+            ym--;
 
-        if(y == 0 || ym == 0)
+        if(y == 0)
             break;
-        y--; ym--;
+        y--;
     }
 }