#!/bin/sh

infile=$1
prefix=tmp-page

rm -f $prefix*p?m   # clean up

# convert pages to raster images
gs -sDEVICE=ppmraw -r30 -sOutputFile=$prefix%03d.ppm -dNOPAUSE -dBATCH -q "$infile"

for img in $prefix*.ppm ; do   # for each page
   ppmtopgm $img > $img.pgm                  # convert to grayscale
   pgmtoppm '#fff' $img.pgm > $img.pgm.ppm   # convert back to RGB
   pnmpsnr $img $img.pgm.ppm                 # diff
done