#!/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

##</code><code>##

%!PS
/Helvetica findfont 50 scalefont setfont
/text (PerlMonks rocks!) def

% page 1 - black
100 500 moveto text show
100 400 moveto text show
showpage

% page 2 - gray
0.5 setgray
100 500 moveto text show
100 400 moveto text show
showpage

% page 3 - color (black and red)
0 setgray
100 500 moveto text show
1 0 0 setrgbcolor          % red
100 400 moveto text show
showpage

##</code><code>##

pnmpsnr: PSNR between tmp-page001.ppm and tmp-page001.ppm.pgm.ppm:
pnmpsnr: Y color component doesn't differ.
pnmpsnr: Cb color component  doesn't differ.
pnmpsnr: Cr color component doesn't differ.
pnmpsnr: PSNR between tmp-page002.ppm and tmp-page002.ppm.pgm.ppm:
pnmpsnr: Y color component doesn't differ.
pnmpsnr: Cb color component  doesn't differ.
pnmpsnr: Cr color component doesn't differ.
pnmpsnr: PSNR between tmp-page003.ppm and tmp-page003.ppm.pgm.ppm:
pnmpsnr: Y  color component: 81.71 dB
pnmpsnr: Cb color component: 35.86 dB
pnmpsnr: Cr color component: 26.43 dB