Function DecompressBC2

trinity/UI/Tr2MouseCursor.cpp:180–219

-------------------------------------------------------------------------------------- Description: Helper function to decompress BC2 format image into B8G8R8A8 format. Used by mouse cursors, which are small and are cached, so the function doesn't have to be super- optimal. Also flips image vertically for DX11 and GL since DX and WINAPI use different origin. Arguments: dest - Destination buffer so

//   pitch - Destination image pitch
// --------------------------------------------------------------------------------------
static void DecompressBC2( char* dest, const char* source, unsigned width, unsigned height, unsigned pitch )
{
	for( unsigned j = 0; j < height; j += 4 )
	{
		for( unsigned i = 0; i < width; i += 4 )
		{
			unsigned color0 = *reinterpret_cast<const unsigned short*>( source + 8 );
			unsigned color1 = *reinterpret_cast<const unsigned short*>( source + 8 + 2 );
			unsigned bits = *reinterpret_cast<const unsigned*>( source + 8 + 4 );
			for( unsigned y = 0; y < 4; ++y )
			{
				for( unsigned x = 0; x < 4; ++x )
				{
					unsigned destY = j + y;
					destY = height - 1 - destY;

					uint32_t* destPixel = reinterpret_cast<uint32_t*>( dest + destY * pitch + ( x + i ) * sizeof( uint32_t ) );
					unsigned alphaValue = ( *( reinterpret_cast<const unsigned short*>( source ) + y ) >> x * 4 ) & 15;
					alphaValue = alphaValue * 255 / 15;
					switch( ( bits >> 2 * ( 4 * y + x ) ) & 3 )
					{
					case 0:
						*destPixel = ConvertBGR565A8ToBGRA8( color0, alphaValue );
						break;
					case 1:
						*destPixel = ConvertBGR565A8ToBGRA8( color1, alphaValue );
						break;
					case 2:
						*destPixel = ConvertBGR565A8ToBGRA8( ( 2 * color0 + color1 ) / 3, alphaValue );
						break;
					case 3:
						*destPixel = ConvertBGR565A8ToBGRA8( ( color0 + 2 * color1 ) / 3, alphaValue );
						break;
					}
				}
			}
			source += 16;
		}
	}
}

std::unique_ptr<char[]> GetUncompressedBitmap( const Tr2HostBitmap* bitmap )
{