webpjpg.sh

#!/bin/bash

# ---------------------------------------------------------------------------
# webpjpg - Convert WebP images to lossless PNG first, then to JPEG, because
# neither imagemagick nor dwebp supports a direct converstion from WebP to JPEG.
#
# This script requires imagemagick <https://imagemagick.org> and
# libwebp <https://developers.google.com/speed/webp/download> to be installed.

# Copyright 2021, Ivan Boothe <git@rootwork.org>

# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU Affero General Public License as published
# by the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.

# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU Affero General Public License at <http://www.gnu.org/licenses/> for
# more details.

# USAGE
#
# $ ./webpjpg.sh <FILE>
# $ ./webpjpg.sh [-h|--help]

# Revision history:
# 2021-11-29  Updating license (1.2)
# 2021-10-15  Minor cleanup and standardization (1.1)
# 2021-10-11  Initial release (1.0)
# ---------------------------------------------------------------------------

# Standard variables
PROGNAME=${0##*/}
VERSION="1.2"
red=$(tput setaf 1)
green=$(tput setaf 2)
yellow=$(tput setaf 3)
cyan=$(tput setaf 6)
bold=$(tput bold)
reset=$(tput sgr0)

# Error handling
error_exit() {
  local error_message="${red}$1${reset}"

  printf "%s\n" "${PROGNAME}: ${error_message:-"Unknown Error"}" >&2
  exit 1
}

graceful_exit() {
  exit 0
}

signal_exit() {
  local signal="$1"

  case "$signal" in
    INT)
      error_exit "${yellow}Program interrupted by user.${reset}"
      ;;
    TERM)
      printf "\n%s\n" "${red}$PROGNAME: Program terminated.${reset}" >&2
      graceful_exit
      ;;
    *)
      error_exit "${red}$PROGNAME: Terminating on unknown signal.${reset}"
      ;;
  esac
}

# Usage: Separate lines for mutually exclusive options.
usage() {
  printf "%s\n" \
    "${bold}Usage:${reset} ${PROGNAME} <FILE>"
  printf "%s\n" \
    "       ${PROGNAME} [-h|--help]"
}

# Help message for --help
help_message() {
  cat <<-_EOF_

${bold}${PROGNAME} ${VERSION}${reset}
${cyan}
Convert WebP images to lossless PNG first, then to JPEG, because neither
imagemagick nor dwebp supports a direct converstion from WebP to JPEG.${reset}

$(usage)

${bold}Options:${reset}
-h, --help    Display this help message and exit.

_EOF_
}

# Options and flags from command line
while getopts :-:h OPT; do
  if [ "$OPT" = "-" ]; then
    OPT="${OPTARG%%=*}"     # extract long option name
    OPTARG="${OPTARG#$OPT}" # extract long option argument (may be empty)
    OPTARG="${OPTARG#=}"    # remove assigning `=`
  fi
  case "$OPT" in
    h | help)
      help_message
      graceful_exit
      ;;
    ??*) # bad long option
      usage >&2
      error_exit "Unknown option --$OPT"
      ;;
    ?) # bad short option
      usage >&2
      error_exit "Unknown option -$OPTARG"
      ;;
  esac
done
shift $((OPTIND - 1)) # remove parsed options and args from $@ list

# Program variables
file=$1
name="${1%.*}"
if [[ ! $file ]]; then
  usage >&2
  error_exit "Filename must be provided."
fi

# Dependencies
convert=$(command -v convert)
if [[ ! $convert ]]; then
  error_exit "Imagemagick must be installed. Aborting."
fi
dwebp=$(command -v dwebp)
if [[ ! $dwebp ]]; then
  error_exit "libwebp must be installed <https://developers.google.com/speed/webp/download>. Aborting."
fi

printf "%s\n" "${green}Converting webp to jpeg...${reset}"

if [ -f "${file}" ]; then # Make sure file exists
  "$dwebp" "$file" -quiet -o "$name".png
  "$convert" "$name".png "$name".jpg
  rm "$name".png
  printf "%s\n" "${cyan}Image converted to ${reset}${bold}${name}.jpg${reset}"
else
  error_exit "Image file '${file}' not found."
fi