optimag

#!/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 $@