#!/bin/sh

maxwd=200
targetwd=170

find "$1" -type d  | while read dir ; do

  firstimg=`ls -1 "$dir"/*.{png,jpg,jpeg,gif} 2> /dev/null | head -1`

  if [ -n "$firstimg" ]; then

    size=`identify "$firstimg" | sed -e 's/.*\(\<[0-9]\+x[0-9]\+\>\).*/\1/'`
    width="${size//[^0-9]*/}"
    height="${size//*[^0-9]/}"

    if [ "$width" -gt $maxwd ]; then

      targetht=$(( $height * $targetwd / $width ))

      destname="${firstimg##*/}"
      destname="00thumb_${destname%.*}.jpg"
      destpath=`dirname "$firstimg"`

      convert "$firstimg" -thumbnail ${targetwd}x$targht -antialias "$destpath/$destname"

    fi

  fi

done