when you say youre seeing thison a web page, can i ask what type of system yure serving the pages with? wordpress etc? or is it an image generation with php or something? thanks dan
On Sun, May 31, 2015 at 4:25 PM, Jay Smith <[email protected]> wrote: > 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 > _______________________________________________ > gimp-user-list mailing list > List address: [email protected] > List membership: https://mail.gnome.org/mailman/listinfo/gimp-user-list > List archives: https://mail.gnome.org/archives/gimp-user-list > _______________________________________________ gimp-user-list mailing list List address: [email protected] List membership: https://mail.gnome.org/mailman/listinfo/gimp-user-list List archives: https://mail.gnome.org/archives/gimp-user-list
