You may want to try rsrcdump for this task (https://github.com/jorio/rsrcdump). It takes a resource fork as input and spits out modern file formats for a selection of resource types (PICT -> .png, snd -> .aiff, etc.)

I just ran rsrcdump on Glider 4.09 and the resulting PNG files appear to match their PICT counterparts as displayed by ResEdit.

I initially wrote this tool to assist in porting some old games by Pangea Software. If you have some resource fork that fails to convert properly with rsrcdump, just let me know and I'd be happy to try to fix it.