Digging through several sites and partial answers to dynamically changing the image format of requested resources, I found the following answer worked for detection and delivery of webp images.
Adding the following to a .htaccess file should detect if the requesting browser accepts webp. Then it checks the server to see if a webp version of the requested image is available on the server. If both statements are true, the server delivers the webp image in place of the requested png, jpg or jpeg file.
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteCond %{HTTP_ACCEPT} image/webp
RewriteCond %{REQUEST_FILENAME} (.*).(jpe?g|png)$
RewriteCond %1.webp -f
RewriteRule (.+).(jpe?g|png)$ $1.webp [T=image/webp,E=accept:1]
</IfModule>
The net savings on load times is excellent. Now if Google will just decide to support this format in the structured data model, we will be set!
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