HGE

		// Load the color and grayscale textures:
		HTEXTURE grayscaleTex = hge->Texture_Load( "Grayscale.png" );
		HTEXTURE colorTex     = hge->Texture_Load( "Color.png" );
 
		// I'll assume they have both the same dimensions...
		int width  = hge->Texture_GetWidth( colorTex );
		int height = hge->Texture_GetHeight( colorTex );
 
		// Need direct access to pixel data...
		// I'll be writing to the color channel, but only reading from the
		// grayscale (alpha) channel:
		DWORD * alphaChannel = hge->Texture_Lock( grayscaleTex, true );
		DWORD * colorChannel = hge->Texture_Lock( colorTex, false );
 
		for ( int x = 0; x < width; x++ ) {
			for ( int y = 0; y < height; y++ ) {
				DWORD color = colorChannel[y * width + x];
				DWORD gray  = alphaChannel[y * width + x];
 
				// R, G, and B are equal in the grayscale image, so it doesn't
				// matter which one I get:
				unsigned char alpha = (unsigned char) GETR( gray );
 
				// Set this as the color texture's alpha channel:
				color = SETA( color, alpha );
 
				// Put it back into the texture:
				colorChannel[y * width + x] = color;
			}
		}
 
		hge->Texture_Unlock( colorTex );
		hge->Texture_Unlock( grayscaleTex );
 
		// Don't need this anymore:
		hge->Texture_Free( grayscaleTex );