cpng

cpng.sh

#!/bin/sh

IFS=$'\n'
FORCE=0

compress_png () {
    more_args=""

    # Note: I use an "og_" prefix on a file to indicate "opaque and grayscale",
    # "g_" for grayscale, and "o_" for opaque.
    if [[ $1 = og_* ]]; then
        more_args="-c 0"
    elif [[ $1 = g_* ]]; then
        more_args="-c 4"
    elif [[ $1 = o_* ]]; then
        more_args="-c 2"
    fi

    # Add a "[[cpng]]" text tag to the file so we don't spend time 
    pngcrush $more_args -rem alla -text b "[[cpng]]" "[[cpng]]" -e ".png_tmp" "$1"
    optipng -o7 "$f"_tmp
    mv "$f"_tmp "$f"
}


for f in $*
do
    if [ "$f" == "-f" ]; then
        FORCE=1
        continue
    fi

    pngcheck -q -t "$f" | grep -q "[[cpng]]"

    if [ $? -ne 0 ] || [ $FORCE -eq 1 ]; then
        compress_png "$f"
    else
        echo "$f" "already compressed"
    fi
done