Generate webp images from png and jpg files recursively in any web folder (uses webp command line tool)

generate-webp-images

#!/bin/bash

# ---------------------------------------------------------------------------
# Generate WebP Images - Uses cwebp command line tool for Linux
# This will generate / re-generate all webp images for all JPG and PNG files
# Being command line based it is incredibly fast
# If you don't want to re-generate existing files set generateall=0
# If you want to re-generate everything set generateall=1
# USE this script at your own risk and Only if you know what you are doing
# Written by Mitchell Krog - mitchellkrog@gmail.com
# https://github.com/mitchellkrogza
# ---------------------------------------------------------------------------


# -------- #
# SETTINGS #
# -------- #

generateall=0 # <--- Set to 1 to re-generate all webp files / 0 will only generate missing webp files
mydomain="mydomain.com" # <--- Enter your domain / folder name here
directory="/srv/http/${mydomain}/wp-content/uploads/" # <--- Some servers use /var/www change if necessary - Change folder structure as needed
quality=80

# ------------ #
# END SETTINGS #
# ------------ #


if [[ "${generateall}" == 1 ]]
then
    for file in $(find ${directory} -type f \( -name "*.jpg" -o -name "*.png" \))
    do
        echo "converting ${file}"
        cwebp -q ${quality} -lossless ${file} -o "${file%.*}.webp"
    done
else
    for file in $(find ${directory} -type f \( -name "*.jpg" -o -name "*.png" \))
    do
        if test -f "${file%.*}.webp"
        then
            echo "file exists - skipping"
        else
            echo "convert ${file}"
            cwebp -q ${quality} -lossless ${file} -o "${file%.*}.webp"
        fi
    done
fi


exit 0

This is great, I notice you do a lot of WordPress Gists, is there an easy way to have WordPress use the WEBP files instead of the original JPG/PNG files?

Hi @andyg2 it can be done through an .htaccess rewrite or an Nginx rule but I would recommend against it as any non webp compliant browsers would not be able to see any images on the site. The proper way it to use a vary method of serving the images

For apache / htaccess

<IfModule mod_rewrite.c>
	RewriteEngine On
	RewriteCond %{HTTP_ACCEPT} image/webp
	RewriteCond %{REQUEST_FILENAME} (.*)\.(jpe?g|png|gif)$
	RewriteCond %{REQUEST_FILENAME}\.webp -f
	RewriteCond %{QUERY_STRING} !type=original
	RewriteRule (.+)\.(jpe?g|png|gif)$ %{REQUEST_URI}.webp [T=image/webp,L]
</IfModule>
<IfModule mod_headers.c>
	<FilesMatch "\.(jpe?g|png|gif)$">
		Header append Vary Accept
	</FilesMatch>
</IfModule>
AddType image/webp .webp

for Nginx

# WebP rules
# --------------------
location ~* ^.+\.(png|jpe?g)$ {
  add_header Vary Accept;
  	expires 365d;
    access_log off;
    add_header Cache-Control "max-age=31536000, public";
  if ($http_accept !~* "webp"){
    break;
  }
  # Server webp or fallback to jpeg
  try_files $uri$webp_suffix $uri =404;
  }
# ------------------- (WebP rules ends here)

Hi @andyg2 it can be done through an .htaccess rewrite or an Nginx rule. The proper way it to use a vary method of serving the images.

Ooh, I'd never head of Vary Accept, I'll be using this for sure, thanks!

Hi @andyg2 it can be done through an .htaccess rewrite or an Nginx rule. The proper way it to use a vary method of serving the images.

Ooh, I'd never head of Vary Accept, I'll be using this for sure, thanks!

This is essentially what plugins do for you but you only need this short bit of code at server level and no plugins are required to serve webp to appropriate devices.