On Wed, January 21, 2009 05:38, Cristian RodrÃguez wrote:
Felix Miata escribiÃ³:
The differences in md5sum mainly prove the images
are different, not
necessarily the page, but the difference between your screenshots is too
obvious for md5sums to matter.
Sure, but this is computer science ;) you need a verfication method to
know if what your eyes are seeing is true or not, visual perceptions can
vary widely and better not to mention the fact browsers, webservers and
image processing libraries may have a number of nasty bugs.
If you take two screenshots of a browser window with the address bar
visible, in each case with a different url, then of course the image files
will be different. That's only logical.
Also if you save to a file format that saves the modification date+time in
some metadata like EXIF, then your md5sum will be different too.
Use GOOD computer science, not computer scientology. :p
To compare images, you could use imgcmp:
$ imgcmp -f 3111skyline-nemesis.jpg -F 3111skyline-ecstasy.jpg -m rmse
Above zero values means that the images are different.
You could also use The Gimp:
* load the first image
* paste the second image as a the new layer
* set layer mode to difference or subtraction.
If you get a perfectly pitch black result, then they are identical.
Anything else is the difference between the two.
In case you see a very dark grey noise, then your images are probably
almost identical and the difference can be attributed to a different lossy
results on visually comparing the two screenshots.
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