I am now able to extract images in their original form. For now, I've only coded this for the REB 1200 .imp format, but am able to provide these insights:
1. the image is stored in its
original size, not the reduced one you see in the ebook!
(I tried this on a REB 1200 conversion of HarryT's "Pride and Prejudice" and the images looked very good. I attach one sample image, JPEG_11544.jpg, below.)
2. In addition to
PICT (unknown internal format, but
not the Apple (old) image format), these are image formats stored in their own filetype .RES files, namely:
JPEG, GIF , and PNG . This PICT format is not understood by either nconvert or irfanview
3. the original image filename is not retained, but replaced with a image resource ID (2 bytes - 0 to 65535).
I attach the images within the
REBTestDocument_1200.imp ebook from the IMP books forum. The two PICT images are only in the .zip.