comic_optimizer.sh

#!/bin/bash

##
# Author: Paul Martin <paul.a.martin@proton.me>
#
# Description: This script will take a CBR or CBZ
#              file and convery whatever's in it
#              to webp format, and re-package it.
#
# Usage: comic_optimizer.sh [DIRECTORY | FILE]
##

# Abort if no directory/file specified
if [ -z "$1" ]
then
    echo "No directory/file specified!"
    exit 1
fi

##
# Variable definitions
# (I tend to over-variablize things, I know)
##

# Programs
P7Z='' # 7z location
RAR='' # rar location
CWEBP='' # cwebp location

# Locations
TRASH_DIR=$(realpath "$HOME/.Trash/") # Where the original file goes when done
TEMP_DIR='' # Where we do the work, recommended to put in /tmp/
FINAL_DIR='' # Where the finished file goes

##
# If your version of `rar` isn't working or installed,
# you're gonna have a bad time.  This happens with macOS
# brew.  Unsure how to fix other than to re-install it
# or go to "Settings > Privacy & Security" and clicking
# the "Just run it anyway" button, whatver that is.
##

if ! "${RAR}" > /dev/null 2>&1;
then
    echo "RAR is missing or broken - fix it"
    IFS=$SAVEIFS
    exit 1
fi

SAVEIFS=$IFS
IFS=$(echo -en "\n\b")

FILES=$(find "$1" -maxdepth 1 -type f -iname "*.cbr" -o -iname "*.cbz")
for FILE in $FILES
do
    KIND=$(file -b "${FILE}")
    FILETYPE=$( echo "${KIND:0:3}" | tr "[:upper:]" "[:lower:]")
    FILENAME=$(basename "${FILE%.*}")
    mkdir "${TEMP_DIR}"

    case "${FILETYPE}" in
        "rar")
            echo "File is a CBR"
            # 7zip doesn't support v5 rar files, so we have to use rar here
            "${RAR}" e -y "${FILE}" "${TEMP_DIR}"
            ;;
        "zip")
            echo "File is a CBZ"
            "${P7Z}" e "${FILE}" -o"${TEMP_DIR}"
            ;;
    esac
    
    ##
    # Here's where the heavy lifting takes place.  Find all the image files,
    # and pipes them into xargs.  Here's an explanation of the flags:
    # -0: input is terminated with a null, used with find's -print0
    # -P0: run the command in an unlimited number of parallel processes
    # -I '{}': names the input
    # cwebp '{}': replaced with the previous input
    # -mt: multi-threaded
    # -short: cwebp can be noisy.  This helps.
    # -progress: should be self-explanatory
    # -o '{}'.webp: append 'webp' to the original filename
    ##

    find -s "${TEMP_DIR}" -type f \( -iname "*.jp*g" -o -iname "*.png" -o -iname "*.gif" \) -print0 | xargs -0 -P0 -I '{}' "${CWEBP}" '{}' -mt -short -progress -o '{}'.webp

    # Now we pack it back up into a CBZ
    "${P7Z}" a -tzip "${TEMP_DIR}"/"$FILENAME".cbz "${TEMP_DIR}"/*.xml "${TEMP_DIR}"/*.webp

    # OPTIONAL: Preserve file modification time
    #touch -r "$OLDFILE" "$NEWNAME"

    # Move it to its final destination
    mv "${TEMP_DIR}"/"$FILENAME".cbz "${FINAL_DIR}"

    # OPTIONAL: Delete the old file
    mv "${FILE}" "${TRASH_DIR}"

    # Delete the temporary directory
    rm -r "${TEMP_DIR}"
done

IFS=$SAVEIFS