The Simpsons - Tapped Out RGB Files

[Daxar]

Do you have the original .rgb file for that image, or are you adding it to the game? The compression/decompression routines look correct for that image (decompressing the "after.rgb" gives an image that looks identical to your "before.png"). I would suspect there's some other file that specifies image format, or something else is going on. Hard to say without a copy of the game myself.