Create a 1080p and a 2160p images from a starting image and apply a watermark

prepare_images.sh

#!/bin/bash

# iterates over all the .jpg files in a directory
# * creates a 1080p version with a 50% transparent signature (if not already present)
# * creates a 2160p version with a 8% transparent signature (if not already present)

FILE_sign_1080=signature_1080.png
FILE_sign_2160=signature_2160.png


# check parameters
if [ -z "$1" ]; then
        echo "Use: $0 <directory_containing_JPGs>"
        exit 1
fi

# remove trailing slash
target_dir="${1%/}"

# make sure it is a valid directory
if [ ! -d "$target_dir" ]; then
        echo "Use: $0 <directory_containing_JPGs>"
        exit 1
fi

# change the Input Field Separator to handle files with spaces
OLD_IFS=$IFS
IFS="$(printf '\n\t')"

# create the destination directories
mkdir "${target_dir}/1080px" "${target_dir}/2160px"

# iterate over the files
for target in ${target_dir}/*.jpg ; do
        echo "Working on $target ..."

        # we want to use a different command for portrait-oriented images
        imagesize=$(identify -format '%wx%h' "$target")
        orientation=""
        w=$(echo $imagesize|cut -dx -f1)
        h=$(echo $imagesize|cut -dx -f2)
        if [ $h -gt $w ]; then
                orientation="portrait"
        fi

        # we need this to build the resized file name
        target_name=$(basename "$target" .jpg)
        target_1080="${target_dir}/1080px/${target_name}_1080.jpg"
        target_2160="${target_dir}/2160px/${target_name}_2160.jpg"

        # create the 1080 pixel image
        if [ ! -f "${target_1080}" ]; then
                echo " - Creating the 1080 pixel image"
                if [ "x${orientation}" == "xportrait" ]; then
                        convert $target -filter lanczos2 -resize "x1080>" -quality 91 tempfile.jpg
                else
                        convert $target -filter lanczos2 -resize "1080^>" -quality 91 tempfile.jpg
                fi
                echo " - Signing the 1080 pixel image"
                composite -dissolve 50% -gravity SouthEast ${FILE_sign_1080} tempfile.jpg ${target_1080}
        fi

        sync

        # create the 2160 pixel image
        if [ ! -f "${target_2160}" ]; then
                echo " - Creating the 2160 pixel image"
                if [ "x${orientation}" == "xportrait" ]; then
                        convert $target -filter lanczos2 -resize "x2160>" -quality 96 tempfile.jpg
                else
                        convert $target -filter lanczos2 -resize "2160^>" -quality 96 tempfile.jpg
                fi
                echo " - Signing the 2160 pixel image"
                composite -dissolve 8% -gravity SouthEast ${FILE_sign_2160} tempfile.jpg ${target_2160}
        fi

        sync
done
IFS=$OLD_IFS

rm -f tempfile.jpg