Comment # 16 on bug 1206322 from Dominique Leuenberger

compare is the function in test.sh, not the command /usr/bin/compare

function compare {
  metric=$1
  image1=$2
  image2=$3
  tolerance=$4
  inversion=$5
  channel=$6

  if [ "$metric" = "PSNR" ]; then
    script="check_compare_PSNR.pl"
  else
    script="check_compare.pl"
  fi

  if [ -z "$channel" ]; then
    channel="Total"
  fi

  if [ ! -f $image1 ]; then
    echo "KO"
    return
  fi

  if [ ! -f $image2 ]; then
    echo "KO"
    return
  fi

  gm compare -metric $metric $image1 $image2 | grep $channel | perl $script
$tolerance $inversion
}

So calling 'compare manually' without the function defined in the scope of
executing compare is not the same as test.sh does

PAE does not reference a file when calling the compare function, but to the
first parameter, metrics.

The name is kinda unfortunate, considering that ImageMAgick delivers a binary
with this name