Half of day 38 complete.

handmade.c

@@ -110,7 +110,11 @@ static void DrawBitmap(game_offscreen_buffer *Buffer, loaded_bitmap *Bitmap, F32
         U32 *Dest = (U32 *)DestRow;
         U32 *Source = SourceRow;
         for(S32 X = MinX; X < MaxX; X++) {
-            *Dest++ = *Source++;
+            if((*Source >> 24) > 128)
+                *Dest = *Source;
+
+            Dest++;
+            Source++;
         }
         DestRow += Buffer->Pitch;
         SourceRow -= Bitmap->Width;
@@ -147,29 +151,43 @@ static loaded_bitmap DEBUGLoadBMP(thread_context *Thread, debug_read_file_result
     loaded_bitmap Result;
     memset(&Result, 0, sizeof(Result));
 
-    // NOTE: Byte order in memory is AA BB GG RR, bottom up.
-    // Littel-endian: 0xRRGGBBAA
-
     debug_read_file_result ReadResult = DEBUGPlatformReadEntireFile(Thread, FileName);
     if(ReadResult.ContentsSize > 0) {
         bitmap_header *Header = (bitmap_header *)ReadResult.Contents;
 
         U32 *Pixels = (U32 *)((U8 *)ReadResult.Contents + Header->BitmapOffset);
         Result.Pixels = Pixels;
-        Result.Width = Header->Width;
+        Result.Width  = Header->Width;
         Result.Height = Header->Height;
 
-        // TODO: Is this too outdated? As of 2026, this loads fine on little-endian.
-        //       Maybe my BMP uses a newer format.
-        /*
+        // NOTE: The byte order in memory is determined by the Header.
+
+        U32 RedMask   = Header->RedMask;
+        U32 GreenMask = Header->GreenMask;
+        U32 BlueMask  = Header->BlueMask;
+        U32 AlphaMask = ~(RedMask | GreenMask | BlueMask);
+
+        bit_scan_result RedShift   = FindLeastSignificantSetBit(RedMask);
+        bit_scan_result GreenShift = FindLeastSignificantSetBit(GreenMask);
+        bit_scan_result BlueShift  = FindLeastSignificantSetBit(BlueMask);
+        bit_scan_result AlphaShift = FindLeastSignificantSetBit(AlphaMask);
+
+        ASSERT(RedShift.Found);
+        ASSERT(GreenShift.Found);
+        ASSERT(BlueShift.Found);
+        ASSERT(AlphaShift.Found);
+
         U32 *SourceDest = Pixels;
         for(S32 Y = 0; Y < Header->Height; Y++) {
             for(S32 X = 0; X < Header->Width; X++) {
-                *SourceDest = (*SourceDest >> 8) | (*SourceDest << 24);
-                SourceDest++;
+                U32 C = *SourceDest;
+
+                *SourceDest = ((((C >> AlphaShift.Index) & 0xFF) << 24) |
+                               (((C >> RedShift.Index  ) & 0xFF) << 16) |
+                               (((C >> GreenShift.Index) & 0xFF) <<  8) |
+                               (((C >> BlueShift.Index ) & 0xFF) <<  8));
             }
         }
-        */
     }
 
     return Result;