This was taken from the Gimp Developers mailing list.
> The photocd plugin, written by Gerd Knorr (email@example.com) > works great but has only the following resolutions: > * width = 192; height = 128 > * width = 384; height = 256 > * width = 768; height = 512
The PhotoCD format contains several layers of resolution. The smaller ones (listed above) have no real data compression, just a bit of subsampling on the chroma channel, so that readout and display can be very fast even on computers without impressive CPUs. The larger resolutions are encoded with a much more sophisticated data compression algorithm, otherwise they would swamp the disk space.
Thus, fiddling with the seek values isn't ever going to give the results you wanted. One quick way to get what you want is to use the hpcdtoppm utility by Hadmut Danisch ( ftp://ftp.gwdg.de/pub/linux/hpcdtoppm/). This will let you convert the image to ppm format, at which point you can easily mess with it in the gimp.
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