#!/bin/sh

convert_size()
{
 echo -n "pattern for matching files (\"*\", \"*.jpg\" etc.): "
 read pattern

 echo -n "size of the new images (e.g. \"800x600\"): "
 read size

 for image in $pattern; do
	convert -verbose "$image" -geometry "$size" "$image"
 done
}

convert_format()
{
 echo -n "pattern for matching files (\"*\", \"*.jpg\" etc.): "
 read pattern

 echo -n "format of the new images (e.g. \"png\"): "
 read format

 for image in $pattern; do	# replace everything behind the last dot by $format
	convert -verbose "$image" $(echo $image | sed -r "s/\.[a-z]{2,4}$/.$format/")
 done
}

echo "[1] convert image size"
echo "[2] convert image format"
read choice

echo

case "$choice" in
  1)	convert_size;
  	;;
  2)	convert_format;
  	;;
esac