I hesitate to directly report this in Bugzilla, because I cannot imagine that nobody else stumbled upon this for about one year, but: It looks like SDL2_image 2.0.3 and 2.0.4 cannot load ILBM images with the “usual” number of bitplanes as used on the Amiga anymore, that is, ILBM files with either 5 bitplanes (32 colors) or 6 bitplanes (64 colors; EHB mode).
The following commit introduced the problem: http://hg.libsdl.org/SDL_image/rev/97f7f01e0665
The commit message says “lbm: Fail to load images with unsupported/bogus color depth”, and the patch limits ILBM files to either 1, 4, 8 or 24 bitplanes, which seems crazy (at least for typical ILBM files from the Amiga).
Can somebody confirm this problem?
I will happily create a nice bug report for this, but I still have the suspicion that I have overseen something by myself… :-o