On 07/28/2013 03:28 AM, Ofnuts wrote:
On 07/28/2013 02:41 AM, Jay Smith wrote:
Actually it's not a negative... and the changes would be on more than
one bit since the bad image file is about 50% bigger than the good one.
I am sorry that this query is not Gimp specific, but since I use Gimp
to create the images and I don't subscribe to any "images" list, I
hope it will be allowed here. I won't make a habit of it.
From time to time I notice an image in our library or on our website
has "become" negative. This is very unsettling as I have used such
images on our website for years and then all of a sudden I notice in
the middle of a web page an image that is in negative.
Yes, it is theoretically possible that I simply never noticed this,
but I have been finding one every few months now for three or four
years. I know everybody says "I did not do it", but these are images
which have not intentionally been manipulated, processed, or uploaded
to the hosting service for for years. The differences in image
appearance are so dramatic that I just can't believe that they have
been like that all along and I just did not see them.
Also, the images don't seem to suffer any other type of damage. They
just become negative.
In the most recent example case (see links below), only the file
residing on the hosting service has "become" negative. The original
JPEG that I uploaded is still correct! (However, over the last
couple years, I have found an occasional "negative-ized" original
JPEG on our server and also a few "negative-ized" TIFFs on our
server. It seems that the alteration to negative can happen anywhere
along the line.
Since the source JPEG version residing on my server is still okay,
the damage happened either during transfer to the hosting service or
while on the hosting service.
Here is an example (the two are images of slightly different objects,
but the overall appearance is supposed to be extremely similar -- the
person who can determine the difference is a keen-eyed philatelist):
My process: All on Linux. After scanning to TIFF, the images are
edited in Gimp as TIFFs. Then they are processed using a script that
runs various ImageMagick actions to create various sizes (copies) as
JPEGs. The source TIFF is preserved unchanged (and the original TIFF
for the negative example above is CORRECT!). The JPEGs are then
uploaded to a hosting service (in this case all the 'original' JPEGs
still on my server are CORRECT!!).
So... The question is..... is there a bit in an image file that can
be hit by a "stray neutrino" (or whatever happens) that can cause the
image file to "become" negative". If yes for JPEG, is it also
possible for TIFF?
Or, it seems more likely to me, would such a change from positive to
negative require a very large number of changes to the image file?
If the type of occasional damage I am observing in a "small" library
of about 100,000 image files is happening everywhere, to everybody,
to all types of computer files, we are in deep do-do in the long
term. As they say.... "Houston, we have a problem."
But the images aren't even the same size (314x431 vs 312x426), and if
you look closely in the corners the perforations aren't the same (you
can invert the colors of the bad ones to make it more visible). So
these are two images of different stamps.
The 'bad' image has a color profile, and this one may be incorrect.
Hmmm. Answered without reading the end of the post... So these are
indeed different subjects... But if you want anyone to determine what
happens when an image is corrupted you have better provide the
before/after versions of the same image.
A bad hard disk or file system problems can cause A JPEG to become
corrupt but the look is different.
Image hosts often have a cavalier attitude wrt to the images deposited
on them (arbitrary format changes, quality reduction...) but I have
never heard of any adding a color profile.
If that can help the profile seems to be added by some Hewlett-Packard
software, but I've never seen any HP software running on Linux and your
whole process is on Linux.
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