Greetings fellow Gimp Users,

I make images using Gimp, but I assume that this question is not really Gimp specific.


I have tens of thousands of images (postage stamps) on my site. Every now and then when I am looking at a page I discover that the image (a JPEG) has had is colors "sort of inverted". The JPEGs were created in large batches by a script from UNcompressed TIFF images. When I go back and look at the the original TIFF, I discover that its colors are "sort of inverted" -- thus the JPEG is a correct rendition of the appearance of its TIFF source.

Thus the problem is in the TIFF. But, the problem happens now and then, over the course of years. The TIFFs are _not_ being intentionally manipulated in that time. The images was originally okay, now its not. It seems to be completely random, just one image here and there.

Somehow the TIFF is getting corrupted. I am assuming by a memory error or a disk/RAID controller error, or such. The images are still openable in Gimp.

This is only happening to one out perhaps one out of five thousand images, every five years. (I am just *guessing* at the error rate because I only find out about them by randomly coming across them.) But, if I have 40,000 images, that is eight images destroyed every five years. (And often I am not able to replace the image because I no longer have the item.)

This example image was originally created in 2006. I suspect (mostly guessing) that it was corrupted sometime since 2010. There is no reason that it would have been edited since that time and file modification information shows nothing since 2006.

On Ubuntu Linux, using "identify -verbose filename.tif" I can read the header information. The only odd thing (to my eye) is that the create date is 2011 and the modification date is 2006:

Properties:
    date:create: 2011-09-13T11:30:24-04:00
    date:modify: 2006-12-21T00:53:03-05:00

I am guessing that means the corruption may have happened in 2011, even though the filesystems own file datestamp is 2006 and the lsattr command shows nothing unusual.


Here is example of a) the resulting JPEG (just to illustrate the nature of the corruption); b) a similar JPEG to show generally what it is supposed to look like; c) the corrupted TIFF.

Corrupted:
http://jsa.viewimage.net/jsa/web/Lists/Denmark/AdPairs/Spec/re02-pair_used-vf-b_136468_r_l.jpg

Correct image of a similar, but different item:
http://jsa.viewimage.net/jsa/web/Lists/Denmark/AdPairs/Spec/re02-pair_used-vf-a_136467_r_l.jpg

This is the TIFF file (corrupted, but viewable in Gimp; colors are sort-of-inverted) Size 496 KB:
http://jsa.viewimage.net/temp/gimp/re02-pair_used-vf-b_136468.tif

My primary question is whether there is a "particular bit that is getting flipped" that could be "unflipped" by some sort of non-visual editing of the source TIFF file?

My secondary question is whether or not other people have seen this type of problem crop up in large image libraries and what the causes have been?

Any thoughts appreciated.

Jay
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