Fix reading 16-bit (5551) tga images. According to Wikipedia "if the pixel depth is 16 bits, the topmost bit is reserved for transparency." Note that it says transparency and not opacity. Opacity is normally how an alpha channel is interpreted but I've changes the reading code to treat the 1-bit alpha channel as transparency. A zero yields no transparency (i.e. fully opaque).

Author: bluescan

Modules/Image/Src/tImageTGA.cpp

@@ -22,14 +22,24 @@ namespace tImage
 {
 
 
-// Helper functions, enums, and types for parsing DDS files.
+// Helper functions, enums, and types for parsing TGA files.
 namespace tTGA
 {
 	#pragma pack(push, r1, 1)
 	struct Header
 	{
 		int8 IDLength;
 		int8 ColourMapType;
+
+		// 0   -  No image data included.
+		// 1   -  Uncompressed, color-mapped images.
+		// 2   -  [Supported] Uncompressed, RGB images.
+		// 3   -  Uncompressed, black and white images.
+		// 9   -  Runlength encoded color-mapped images.
+		// 10  -  [Supported] Runlength encoded RGB images.
+ 		// 11  -  Compressed, black and white images.
+		// 32  -  Compressed color-mapped data, using Huffman, Delta, and runlength encoding.
+		// 33  -  Compressed color-mapped data, using Huffman, Delta, and runlength encoding. 4-pass quadtree-type process.
 		int8 DataTypeCode;
 		int16 ColourMapOrigin;
 		int16 ColourMapLength;
@@ -247,7 +257,11 @@ void tImageTGA::ReadColourBytes(tColour4b& dest, const uint8* src, int bytesPerP
 			dest.R = (src[1] & 0x7c) << 1;
 			dest.G = ((src[1] & 0x03) << 6) | ((src[0] & 0xe0) >> 2);
 			dest.B = (src[0] & 0x1f) << 3;
-			dest.A = (src[1] & 0x80);
+
+			// According to Wikipedia: If the pixel depth is 16 bits, the topmost bit is reserved for transparency.
+			// Me: Note that it says transparency and not opacity. Opacity is normally how an alpha channel is interpreted.
+			// The code below treats the 1-bit alpha channel as transparency. A zero yields no transparency (fully opaque).
+			dest.A = (src[1] & 0x80) ? 0 : 255;
 			break;
 
 		default: