The graphic format used in the visual novel "SHUFFLE!" (シャッフル!) is quite interesting because the compression algorithm is very efficient for its size and simplicity. It reaches a compression ratio of sometimes 6:1 in just around 40 lines of C , which definitely isn't too shabby. A prerequisite for getting a good compression ratio using this algorithm is that the images have many neighbouring pixels with the same color though.

I wrote a small image converter, which takes GPD files and a target directory as arguments. The images are then converted to PNG and placed in the target directory.

An unpacker for the PAC packages can be found here and my GPD viewer is here


If you placed it in the game-directory, open a terminal in that folder (shift+right click, open in command line in windows 7+) and type e.g.

gpd_convert Bg\* Bg

to convert all files in the Bg directory into pngs and place them next to their gpd counter-parts.



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