<<My first thought was that since a JPEG is a compressed format, a random change to any bit (in the bits and bytes computer-talk sense) would likely break the file.>> My guess is that it would depend in which byte you changed the bit ;o) With jpeg not all parts of the file are compressed and the parts that are are fairly modular - you might for instance "harm" only one 8x8 pixel block in one case or confuse it by changing the number of rows from 512 to 1536 in another. LZW compressed TIFFs are probably less tolerant. You have me eager to play here though: writing a mini bit of code to flip a single bit in a file is a doddle. I must try: run it 100 times and try to open the target jpeg. << I just fooled around with a small JPEG, changing one bit here, and another bit there. 8 changes and each time the JPEG looked no worse for wear.>> Oh, you already tried ;o) <<Run the card through whatever you're testing. While your there, why stop at 10 ;-) Use any number of tools to determine if the card version and the reference version are bit for bit identical or not. >> A potential problem in this approach is inherent error correction - even if a single bit is changed on the disk byt the time you read the file it may have been corrected for you. To be sure you need to read the card directly. But of course, I was thinking of disks: maybe cards don't have any error checking. Bob -- Whatever you Wanadoo: http://www.wanadoo.co.uk/time/ This email has been checked for most known viruses - find out more at: http://www.wanadoo.co.uk/help/id/7098.htm
