Using webp format

From EE's documentation, it's unclear if the manipulations would work with the {exp:file:entries} tag or not. If the on-the-fly manipulations do work with that tag, then you should be able to do it something a little like this (untested):

{exp:channel:entries channel="my_channel"}
    {some_ansel_field}
        {exp:file:entries limit="1" file_id="{img:file_id}"}
            <img src="{url:webp}">
        {/exp:file:entries}
    {/some_ansel_field}
{/exp:channel:entries}

As I say, I have no idea if that will work, but that's the only possibility since EE's docs only list the on-the-fly manipulation as part of the native file field-type and I have no way to test at the moment.