Optimize JPEG, PNG and SVG images with one simple command.

optimag.sh

#!/bin/bash
set -euo pipefail
IFS=$'\n\t'

get_file_mime_type()
{
    local filename=$1

    file -b --mime-type "$filename"
}

get_files_in_working_directory()
{
    local files=''

    for filename in ./*; do
        case $(get_file_mime_type "$filename") in
            "image/png"|"image/jpeg"|"image/svg"|"image/svg+xml")
                files+="$filename\n"
            ;;
        esac
    done

    echo -ne "$files"
}

optimize_file()
{
    local filename=$1

    case $(get_file_mime_type "$filename") in
        "image/png")
            # http://www.kompresja-grafiki-rastrowej-png-gif.cba.pl/
            (set -x +e
                optipng -o7 -zm1-9 "$filename"
                pngcrush -brute -ow "$filename"
                pngout "$filename" "$filename" -y
                advpng -z4 "$filename"
            ) || true
        ;;
        "image/jpeg")
            # https://guides.wp-bullet.com/batch-optimize-jpg-lossy-linux-command-line-with-jpeg-recompress/
            (set -x +e
                jpegoptim --strip-all "$filename"
                jpeg-recompress --quality medium --method smallfry --accurate \
                    --min 80 --max 92 "$filename" "$filename"
            ) || true
        ;;
        "image/svg"|"image/svg+xml")
            (set -x +e
                svgo -i "$filename"
            ) || true
        ;;
    esac
}

main()
{
    for binary in "optipng" "advpng" "pngcrush" "pngout" "jpegoptim" "jpeg-recompress" "svgo"; do
        if ! command -v $binary > /dev/null; then
            echo "Error: there is no \"$binary\" binary."
            exit 1
        fi
    done

    if [[ -n "$@" ]]; then
        local files=("$@")
    else
        read -p "Are you sure you want to optimize all images in cwd? (yes/no) "
        if [[ $REPLY != "yes" ]]; then
            exit
        fi

        local files=$(get_files_in_working_directory)

        if [[ -z $files ]]; then
            echo "There is no images here."
            exit 1
        fi
    fi

    for filename in ${files[*]}; do
        echo -e "\n\033[1;33m→ $filename\e[0m\n"
        optimize_file "$filename"
    done
}

main $@