#! /bin/sh
# #############################################################################

       NAME_="pngoptim"
       HTML_="optimize png files"
    PURPOSE_="reduce the size of a PNG file if possible"
   SYNOPSIS_="$NAME_ [-hl] <file> [file...]"
   REQUIRES_="standard GNU commands, pngcrush"
    VERSION_="1.0"
       DATE_="2004-06-29; last update: 2004-12-30"
     AUTHOR_="Dawid Michalczyk <dm@eonworks.com>"
        URL_="www.comp.eonworks.com"
   CATEGORY_="gfx"
   PLATFORM_="Linux"
      SHELL_="bash"
 DISTRIBUTE_="yes"

# #############################################################################
# This program is distributed under the terms of the GNU General Public License

usage() {

echo >&2 "$NAME_ $VERSION_ - $PURPOSE_
Usage: $SYNOPSIS_
Requires: $REQUIRES_
Options:
     -h, usage and options (this help)
     -l, see this script"
exit 1
}

# tmp file set up
tmp_1=/tmp/tmp.${RANDOM}$$

# signal trapping and tmp file removal
trap 'rm -f $tmp_1 >/dev/null 2>&1' 0
trap "exit 1" 1 2 3 15

# var init
old_total=0
new_total=0

# arg handling and main execution
case "$1" in

    -h) usage ;;
    -l) more $0; exit 1 ;;
     *.*) # main execution

        # check if required command is in $PATH variable
        which pngcrush &> /dev/null
        [[ $? != 0 ]] && { echo >&2 required \"pngcrush\" command is not in your PATH; exit 1; }

        for a in "$@";do
            if [ -f $a ] && [[ ${a##*.} == [pP][nN][gG] ]]; then
                old_size=$(ls -l $a | { read b c d e f g; echo $f ;} )
                echo -n "${NAME_}: $a $old_size -> "
                pngcrush -q $a $tmp_1
                rm -f -- $a
                mv -- $tmp_1 $a
                new_size=$(ls -l $a | { read b c d e f g; echo $f ;} )
                echo $new_size bytes
                (( old_total += old_size ))
                (( new_total += new_size ))
            else
                echo ${NAME_}: file $a either does not exist or is not a png file
            fi
        done ;;

    *) echo ${NAME_}: skipping $1 ; continue ;;

esac

percentage=$(echo "scale = 2; ($new_total*100)/$old_total" | bc)
reduction=$(echo $(( old_total - new_total )) \
| sed '{ s/$/@/; : loop; s/\(...\)@/@.\1/; t loop; s/@//; s/^\.//; }')
echo "${NAME_}: total size reduction: $reduction bytes (total size reduced to ${percentage}%)"