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

Hartmut Henkel hartmut_henkel at gmx.de
Thu Mar 16 20:23:34 CET 2006

pnmpsnr seems to work quite nicely, e. g. with some file xx.tex:

  \input tufte \input tufte \input tufte

  \hbox{\kern 0.1pt a}

  \input tufte \input tufte

against another file with 0pt instead of 0.1pt kern one gets:

$ pdftoppm -r 1200 xx.pdf xx
$ pdftoppm -r 1200 yy.pdf yy
$ pnmpsnr xx-000001.ppm yy-000001.ppm
pnmpsnr: PSNR between xx-000001.ppm and yy-000001.ppm:
pnmpsnr: Y  color component: 59.18 dB
pnmpsnr: Cb color component  doesn't differ.
pnmpsnr: Cr color component doesn't differ.

(seems there is a spurious blank in the output :-) but such a tiny
displacement needs rendering at 1200 dpi which gives large files and is

Regards, Hartmut

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