Losslessly convert all JPGs in current folder to JPEG-XL preserving EXIF and mtime. (Bash script)

convert_jpg_to_jxl.sh

#!/bin/bash

# Check files with `jpg` extension
if [[ -n $(shopt -s nullglob; echo *.jpg) ]]; then
    # Create a directory to work in
    mkdir -p wrk
    # Move all files with `jpg` extension, as well as XMP sidecars to the working directory
    mv ./*.jpg wrk
    if [[ -n $(shopt -s nullglob; echo *.jpg.xmp) ]]; then
        mv ./*.jpg.xmp wrk
    fi
    cd wrk || exit

    # Convert all JPEG files to JPEG-XL format losslessly
    parallel 'cjxl --num_threads 1 -j 1 -e 10 {} {.}.jxl' ::: *.jpg

    # For each JPEG-XL file, copy metadata from the original JPEG file, and then delete the original JPEG file
    if [[ -n $(shopt -s nullglob; echo *.jxl) ]]; then
        parallel 'exiftool -m -overwrite_original -api compress=1 -tagsfromfile {.}.jpg {}; touch -r {.}.jpg {}; rm {.}.jpg' ::: *.jxl
    fi

    # If there are still non converted JPEG files
    if [[ -n $(shopt -s nullglob; echo *.jpg) ]]; then
        mkdir -p out

        # Transform then, without changes, this usually remakes the Huffman tables, that is the most common source of errors when converting to JPEG-XL (commonly found in WhatsApp images)
        parallel 'echo {}; jpegtran -copy all -optimize -perfect -strict -outfile out/{} {}' ::: *.jpg

        # For each JPEG-XL file, copy metadata from the original JPEG file, and then delete the original JPEG file
        if [[ -n $(shopt -s nullglob; echo out/*.jpg) ]]; then
            parallel 'cjxl --num_threads 1 -j 1 -e 10 out/{} {.}.jxl; exiftool -m -overwrite_original -api compress=1 -tagsfromfile {} {.}.jxl; touch -r {} {.}.jxl; rm {} out/{}' ::: *.jpg
        fi

        rmdir out
    fi

    # Rename XMP sidecars to match the new JPEG-XL files, if any
    if [[ -n $(shopt -s nullglob; echo *.jpg.xmp) ]]; then
        for i in *.jpg.xmp
            do k="${i%.jpg.xmp}.jxl.xmp"
            if [[ -f "${i%.jpg.xmp}.jxl" ]]; then
                mv "$i" "$k"
            fi
        done
    fi

    # Move all files back to the parent directory
    find . -empty -delete
    mv ./* ..
    cd ..
    rmdir wrk
fi

# Check files with `JPG` extension
if [[ -n $(shopt -s nullglob; echo *.JPG) ]]; then
    # Create a directory to work in
    mkdir -p wrk
    # Move all files with `JPG` extension, as well as XMP sidecars to the working directory
    mv ./*.JPG wrk
    if [[ -n $(shopt -s nullglob; echo *.JPG.xmp) ]]; then
        mv ./*.JPG.xmp wrk
    fi
    if [[ -n $(shopt -s nullglob; echo *.JPG.XMP) ]]; then
        mv ./*.JPG.XMP wrk
    fi
    cd wrk || exit

    # Convert all JPEG files to JPEG-XL format losslessly
    parallel 'cjxl --num_threads 1 -j 1 -e 10 {} {.}.JXL' ::: *.JPG

    # For each JPEG-XL file, copy metadata from the original JPEG file, and then delete the original JPEG file
    if [[ -n $(shopt -s nullglob; echo *.JXL) ]]; then
        parallel 'exiftool -m -overwrite_original -api compress=1 -tagsfromfile {.}.JPG {}; touch -r {.}.JPG {}; rm {.}.JPG' ::: *.JXL
    fi

    # If there are still non converted JPEG files
    if [[ -n $(shopt -s nullglob; echo *.JPG) ]]; then
        mkdir -p out

        # Transform then, without changes, this usually remakes the Huffman tables, that is the most common source of errors when converting to JPEG-XL (commonly found in WhatsApp images)
        parallel 'echo {}; jpegtran -copy all -optimize -perfect -strict -outfile out/{} {}' ::: *.JPG

        # For each JPEG-XL file, copy metadata from the original JPEG file, and then delete the original JPEG file
        if [[ -n $(shopt -s nullglob; echo out/*.JPG) ]]; then
            parallel 'cjxl --num_threads 1 -j 1 -e 10 out/{} {.}.JXL; exiftool -m -overwrite_original -api compress=1 -tagsfromfile {} {.}.JXL; touch -r {} {.}.JXL; rm {} out/{}' ::: *.JPG
        fi

        rmdir out
    fi

    # Rename XMP sidecars to match the new JPEG-XL files, if any
    if [[ -n $(shopt -s nullglob; echo *.JPG.xmp) ]]; then
        for i in *.JPG.xmp
            do k="${i%.JPG.xmp}.JXL.xmp"
            if [[ -f "${i%.JPG.xmp}.JXL" ]]; then
                mv "$i" "$k"
            fi
        done
    fi

    if [[ -n $(shopt -s nullglob; echo *.JPG.XMP) ]]; then
        for i in *.JPG.XMP
            do k="${i%.JPG.XMP}.JXL.XMP"
            if [[ -f "${i%.JPG.XMP}.JXL" ]]; then
                mv "$i" "$k"
            fi
        done
    fi

    # Move all files back to the parent directory
    find . -empty -delete
    mv ./* ..
    cd ..
    rmdir wrk
fi

# Check files with `jpeg` extension
if [[ -n $(shopt -s nullglob; echo *.jpeg) ]]; then
    # Create a directory to work in
    mkdir -p wrk
    # Move all files with `jpeg` extension, as well as XMP sidecars to the working directory
    mv ./*.jpeg wrk
    if [[ -n $(shopt -s nullglob; echo *.jpeg.xmp) ]]; then
        mv ./*.jpeg.xmp wrk
    fi
    cd wrk || exit

    # Convert all JPEG files to JPEG-XL format losslessly
    parallel 'cjxl --num_threads 1 -j 1 -e 10 {} {.}.jxl' ::: *.jpeg

    # For each JPEG-XL file, copy metadata from the original JPEG file, and then delete the original JPEG file
    if [[ -n $(shopt -s nullglob; echo *.jxl) ]]; then
        parallel 'exiftool -m -overwrite_original -api compress=1 -tagsfromfile {.}.jpeg {}; touch -r {.}.jpeg {}; rm {.}.jpeg' ::: *.jxl
    fi

    # If there are still non converted JPEG files
    if [[ -n $(shopt -s nullglob; echo *.jpeg) ]]; then
        mkdir -p out

        # Transform then, without changes, this usually remakes the Huffman tables, that is the most common source of errors when converting to JPEG-XL (commonly found in WhatsApp images)
        parallel 'echo {}; jpegtran -copy all -optimize -perfect -strict -outfile out/{} {}' ::: *.jpeg

        # For each JPEG-XL file, copy metadata from the original JPEG file, and then delete the original JPEG file
        if [[ -n $(shopt -s nullglob; echo out/*.jpeg) ]]; then
            parallel 'cjxl --num_threads 1 -j 1 -e 10 out/{} {.}.jxl; exiftool -m -overwrite_original -api compress=1 -tagsfromfile {} {.}.jxl; touch -r {} {.}.jxl; rm {} out/{}' ::: *.jpeg
        fi

        rmdir out
    fi

    # Rename XMP sidecars to match the new JPEG-XL files, if any
    if [[ -n $(shopt -s nullglob; echo *.jpeg.xmp) ]]; then
        for i in *.jpeg.xmp
            do k="${i%.jpeg.xmp}.jxl.xmp"
            if [[ -f "${i%.jpeg.xmp}.jxl" ]]; then
                mv "$i" "$k"
            fi
        done
    fi

    # Move all files back to the parent directory
    find . -empty -delete
    mv ./* ..
    cd ..
    rmdir wrk
fi

# Check files with `JPEG` extension
if [[ -n $(shopt -s nullglob; echo *.JPEG) ]]; then
    # Create a directory to work in
    mkdir -p wrk
    # Move all files with `JPEG` extension, as well as XMP sidecars to the working directory
    mv ./*.JPEG wrk
    if [[ -n $(shopt -s nullglob; echo *.JPEG.xmp) ]]; then
        mv ./*.JPEG.xmp wrk
    fi
    if [[ -n $(shopt -s nullglob; echo *.JPEG.XMP) ]]; then
        mv ./*.JPEG.XMP wrk
    fi
    cd wrk || exit

    # Convert all JPEG files to JPEG-XL format losslessly
    parallel 'cjxl --num_threads 1 -j 1 -e 10 {} {.}.JXL' ::: *.JPEG

    # For each JPEG-XL file, copy metadata from the original JPEG file, and then delete the original JPEG file
    if [[ -n $(shopt -s nullglob; echo *.JXL) ]]; then
        parallel 'exiftool -m -overwrite_original -api compress=1 -tagsfromfile {.}.JPEG {}; touch -r {.}.JPEG {}; rm {.}.JPEG' ::: *.JXL
    fi

    # If there are still non converted JPEG files
    if [[ -n $(shopt -s nullglob; echo *.JPEG) ]]; then
        mkdir -p out

        # Transform then, without changes, this usually remakes the Huffman tables, that is the most common source of errors when converting to JPEG-XL (commonly found in WhatsApp images)
        parallel 'echo {}; jpegtran -copy all -optimize -perfect -strict -outfile out/{} {}' ::: *.JPEG

        # For each JPEG-XL file, copy metadata from the original JPEG file, and then delete the original JPEG file
        if [[ -n $(shopt -s nullglob; echo out/*.JPEG) ]]; then
            parallel 'cjxl --num_threads 1 -j 1 -e 10 out/{} {.}.JXL; exiftool -m -overwrite_original -api compress=1 -tagsfromfile {} {.}.JXL; touch -r {} {.}.JXL; rm {} out/{}' ::: *.JPEG
        fi

        rmdir out
    fi

    # Rename XMP sidecars to match the new JPEG-XL files, if any
    if [[ -n $(shopt -s nullglob; echo *.JPEG.xmp) ]]; then
        for i in *.JPEG.xmp
            do k="${i%.JPEG.xmp}.JXL.xmp"
            if [[ -f "${i%.JPEG.xmp}.JXL" ]]; then
                mv "$i" "$k"
            fi
        done
    fi

    if [[ -n $(shopt -s nullglob; echo *.JPEG.XMP) ]]; then
        for i in *.JPEG.XMP
            do k="${i%.JPEG.XMP}.JXL.XMP"
            if [[ -f "${i%.JPEG.XMP}.JXL" ]]; then
                mv "$i" "$k"
            fi
        done
    fi

    # Move all files back to the parent directory
    find . -empty -delete
    mv ./* ..
    cd ..
    rmdir wrk
fi