#!/bin/bash

# compressJPG.sh: compress a JPG with mozjpeg if the savings are worthwhile.
# Author: Gwern Branwen
# Date: 2020-02-07
# When:  Time-stamp: "2025-09-30 17:36:48 gwern"
# License: CC-0

set -e

if [ $# -eq 0 ]; then
    echo "Error: No arguments given!"
    exit -1;
else

    command -v jpegtran > /dev/null
    command -v mogrify > /dev/null

    JPG="$(mktemp /tmp/XXXXXX-original.jpg)";
    TMP="$(mktemp /tmp/XXXXXX-temp.jpg)"
    cp "$1" "$JPG"
    jpegtran -copy none -progressive -optimize -outfile "$TMP" "$JPG"
    mogrify -quality 60 "$TMP"

    ORIGINAL=$(wc --chars < "$JPG")
    SMALL=$(wc --chars < "$TMP")
    RATIO=$(echo "$ORIGINAL / $SMALL" | bc --mathlib)
    echo "$1 : from $ORIGINAL to $SMALL ($RATIO)"

    if (( $(echo "$RATIO > 1.2" | bc --mathlib) ));
    then
        mv "$TMP" "$1"
    fi
    rm "$JPG" "$TMP" &> /dev/null || true

    shift;
    if [ $# -eq 0 ]; then exit 0; else compressJPG "$@"; fi;
fi