On Sun, May 31, 2015 at 4:25 PM, Jay Smith <j...@jaysmith.com
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:
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.
Correct image of a similar, but different item:
This is the TIFF file (corrupted, but viewable in Gimp; colors are
sort-of-inverted) Size 496 KB:
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
Any thoughts appreciated.
On 05/31/2015 08:46 PM, Daniel Smith wrote:
> 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?
When I say I saw it on a web page, all I meant is that was where I was
looking when I noticed the corrupted file (JPEG version thereof).
All viewing (of both the JPEG and the original TIFF that the JPEG was
made from) after that time has been done using Gimp to view the
The fact that I first noticed the corrupted JPEG on a web page was not
relevant and I should not have included that detail. I only mentioned
it that way because that is the only way I actually would notice that
one of tens of thousands of files had been corrupted. I don't
systematically go through and view the library of files just for fun.
I am sorry for the misleading detail.
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