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February 2010

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2010.02.10 17:43 "Using tiffcmp for comparing images", by Richard Nolde

Debora,
    I believe that you can use the -l option to tiffcmp to contine past 
the first differing byte and generate a list of all the bytes that 
differ.  You can pipe that output to wc and see how many 
words/lines/bytes have been reported to get a gross estimate of the 
number of difference bytes and test that against a threshold you 
determine empirically if that meets your needs.
> Hi,
>
> tiffcmp could be useful if it didn't stop when it finds the first
> difference between the files. What if there is only one pixel different?
> for the person that reads the fax it should be imperceptible. Only one, or
> two... or maybe a hundred pixels shouldnt be a problem depending on the
> content of the image. That's why I need to compare all the data. You made
> a good poing though. Thank you so much.
>
> Debora
>
>   From the tiffcmp man page:
>
> NAME
>         tiffcmp - compare two TIFF files
>
>    By default, tiffcmp will terminate if it encounters any difference.
>
>
> OPTIONS
>         -l     List each byte of image data that differs between the
> files.
>