Turn @2x images into @1x on the command line.

README.md

This is a simple Bash function that will (should?) turn any @2x image into a non-retina version.

Usage

Place the contents of deretinize.sh in your .bashrc, .bash_profile, or any other file that will get executed when you load your shell. Then,

$ deretinize xyz@2x.png

This will output a file named xyz.png in the same directory. If the original image has odd dimensions, the script will resize it appropriately.

deretinize.sh

function deretinize() {
    INPUT=$1
    DIMENSIONS=`dimensions $INPUT`
    GRAVITY=""
    UPDATED_DIMENSIONS=""
    HALF_DIMENSIONS=""
    INDEX=0
    for VALUE in `echo $DIMENSIONS | tr "x" "\n"`; do
        if [ $INDEX -eq 0 ]; then
            DIRECTION="west";
        else
            DIRECTION="south";
            UPDATED_DIMENSIONS+="x"
            HALF_DIMENSIONS+="x"
        fi

        if [ $(( VALUE % 2 )) -eq 1 ]; then
            GRAVITY+=$DIRECTION
            UPDATED_DIMENSIONS+=$((VALUE+1))
            HALF_DIMENSIONS+=$(((VALUE+1) / 2))
        else
            UPDATED_DIMENSIONS+=$((VALUE))
            HALF_DIMENSIONS+=$((VALUE/2))
        fi

        INDEX=$((INDEX+1))
    done

    if [ -z "$GRAVITY" ]; then
        GRAVITY="center"
    fi

    if [ "$UPDATED_DIMENSIONS" != "$DIMENSIONS" ]; then
        convert $INPUT -background transparent -gravity $GRAVITY -extent $UPDATED_DIMENSIONS $INPUT
    fi

    OUTPUT=`echo $INPUT | sed -E "s/@2x\.(\w*)/.\1/g"`
    convert $INPUT -resize $HALF_DIMENSIONS $OUTPUT
}