Hi All-- I noticed recently that a few of the jpgs from my digital cameras have developed bitrot. Not a real problem, because the cameras are CD Mavicas, and I can simply copy the original from the cd. Except for the fact that I've got nearly 25,000 images to check. So I wrote a set of programs to both index the disk versions with the cd versions, and to compare, using filecmp.cmp(), the cd and disk version. Works fine. Turned up several dozen files that had been inadvertantly rotated or saved with the wrong quality, various fat-fingered mistakes like that.
However, it didn't flag the files that I know have bitrot. I seem to remember that diff uses a checksum algorithm on binary files, not a byte-by-byte comparison. Am I wrong? If I am, what then is the source of the problem in my jpg images where it looks like a bit or two has been shifted or added; suddenly, there's a line going through the picture above which it's normal, and below it either the color has changed (usually to pinkish) or the remaining raster lines are all shifted either right or left? Any ideas? Metta, Ivan ---------------------------------------------- Ivan Van Laningham God N Locomotive Works http://www.andi-holmes.com/ http://www.foretec.com/python/workshops/1998-11/proceedings.html Army Signal Corps: Cu Chi, Class of '70 Author: Teach Yourself Python in 24 Hours -- http://mail.python.org/mailman/listinfo/python-list
