binn

#!/bin/bash -e

if [ $# -lt 3 ]; then
    cat >&2 <<EOF
$(basename $0) <input> <output> <factor>

 Take a photo and shrink it by the binning_factor to improve
 signal to noise ratio.  Binning factor must be a whole number,
 and input image may be cropped slightly to ensure its size is a
 whole number of 'bins'.

 Original Script by Walter Dnes <waltdnes@waltdnes.org>
EOF
    exit 1
fi

source_file=${1}
output_file=${2}
bin_size=${3}

set -$- `identify -format '%w %h' "${1}"`
x=$1   y=$2

newx=$((${x} / ${bin_size}))
checkx=$((${newx} * ${bin_size}))
if [[ ${checkx} -ne ${x} ]]; then
  crop_flag="YES"
fi

newy=$((${y} / ${bin_size}))
checky=$((${newy} * ${bin_size}))
if [[ ${checky} -ne ${y} ]]; then
  crop_flag="YES"
fi

if [ "$crop_flag" ]; then
  crop_args="-crop ${checkx}x${checky}+0+0 +repage"
fi

convert "${source_file}" $crop_args \
        -filter box -resize "${newx}x${newy}" \
        "${output_file}"