[NTG-pdftex] Creating identical PDF files with different pdfTeX runs

[Hartmut Henkel]

On Thu, 16 Mar 2006, Frank Küster wrote:

> Hartmut Henkel <hartmut_henkel at gmx.de> wrote:
>
> Yes, we definitely need the original file.
>
> > Maybe some crosscorrelation between images with some given tolerance
> > limit would be safer.
>
> Any hints what I could use for such a purpose?

just found from Netpbm:

NAME
       pnmpsnr - compute the difference between two portable anymaps

SYNOPSIS
       pnmpsnr [pnmfile1] [pnmfile2]

DESCRIPTION

       Reads two PBM, PGM, or PPM files, or PAM equivalents, as input.
       Prints the peak  signal-to-noise  ratio  (PSNR)  difference
       between the two images. This  metric is typically used in image
       compression papers to rate the distortion between original and
       decoded image.

And in ImageMagick there is a -compose operator with Difference and
Multiply option.

Regards, Hartmut