Batch Convert Images to webp Using BASH

webp is very common nowadays but usually screenshots and other images are available in a different format, e.g. jpg or png. Converting a single image is easy using cwebp. If all files in a folder should be converted, a shell script or command is needed.

Inline it could be done using the following:

for file in *.png; do if [ -f "$file" ]; then cwebp -lossless $file -o "${file%.*}.webp" -quiet ; fi; done

for file in *.jpg; do if [ -f "$file" ]; then cwebp -q 90 $file -o "${file%.*}.webp" -quiet ; fi; done

If a bit more control is needed, a proper bash script is the solution:

#!/bin/bash

image_quality=90
valid_img_file_extensions=("png" "tif" "tiff" "jpg" "jpeg")
folder_path=""
lossless_mode=false

for i in "$@"
do
    case $i in
        -p=*|--folderpath=*)
            folder_path="${i#*=}"
            ;;
        -ext=*|--file-extension=*)
	    valid_img_file_extensions=("${i#*=}")
            ;;
        -q=*|--compression-quality=*)
	    image_quality="${i#*=}"
	    ;;
	-l*|--lossless*)
	    lossless_mode=true
	    ;;
    esac
done

for file in "$folder_path"*
do
    if [ -f $file ]
    then
	    ext=${file#*.}
	    if [[ $valid_img_file_extensions =~ (^|[[:space:]])"$ext"($|[[:space:]]) ]]
	    then
	        output_fn="${file%.*}.webp"
	        if  $lossless_mode
            then
		        cwebp -lossless $file -o $output_fn -quiet
	        else
		        cwebp -q $image_quality $file -o $output_fn -quiet
	        fi
	    fi
    fi
done

The shell script can also be found here.