I have managed to recreate Kevin Bracey’s work in extracting graphics from the Infocom V6 game resources and put them in Blorb files. This entailed translating pix2gif.c from the old Ztools package into Perl, rummaging around the old Blorb files, rummaging around in Infocom’s files, and learning more about the structure of a PNG file. It now works perfectly for the MCGA graphics packages.
PNGs created from the EGA files appear to be okay, but there are ongoing issues with getting SDL Frotz to process the resulting Blorbs correctly. Windows Frotz has identical trouble. Dumb and Curses Frotz have been updated to actually read the resolution chunk rather than assuming 320x200. Their V6 semi-support works fine on EGA Blorbs as long as the resolution chunk is correct.
Creating PNGs from the CGA files is currently a mess. The ones from Zork Zero look okay. PNGs from the other V6 games are all have their IDAT chunks truncated.
I’m still working on getting EGA and CGA Blorbs working.
All the tools I’ve created for doing this are available at https://gitlab.com/DavidGriffith/blorbtools. The main ones are pix2png.pl for the extraction. There’s infoblorb.pl which takes a directory of stuff produced by pix2png.pl and creates a .blurb file describing it all. After some editing of the .blurb file, run pblorb.pl on it and you’ve got a new Blorb file. I don’t believe that Graham’s cblorb can be used in place of pblorb.pl for this.