Re: [Gimp-user] What causes random (in error) image color-inverting of TIFFs, over time? Is it correctable?

["Liam R. E. Quin" <liam holoweb net>]

On Sun, 2015-05-31 at 17:25 -0400, Jay Smith wrote:

> 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?

The nearest I have seen to this that i can remember involves software 
changes - e.g. a different version of libtiff or whatever. For 
example, recently some images on  http://www.fromoldbooks.org/appeared 
to break, and it turned out to be a version of the jpeg library that 
had stopped supporting arithmetic encoding (for software patent 
reasons).

TIFF is one of the more complex graphics formats in widespread use; 
for my own part I prefer to use PNG because at least the core image 
part is relatively simple and well-specified and widely supported.

If by any chance you have both an "uncorrupted" and a "corrupted" TIFF 
file, and you know for sure what programs were used to create them and 
on what platform (e.g. Linux on SPARC, Linux on Intel-64, 32-bit 
Windows on Intel, etc) I'm willing to take a look, althogh I don't 
think I have TIFF debugging stuff around any more.

It seems unlikely that the same single-bit error would happen on 
multiple images because of a hard drive problem, especially if a RAID 3
or higher storage system didn't detect it. Not impossible - an 
infinite number of monkeys typing for all eternity might all type 
nothing except page 54 of the January 1936 Great Western Railway 
timetable through Crewe - but I'd look for more likely causes first, 
the most likely of which might be a software change.

Liam


-- 
Liam R. E. Quin <liam holoweb net>
The barefoot typographer


http://www.fromoldbooks.org/ - words & pictures from old books