How can I use wp_save_image_editor_file filter?

The filter inside ~/wp-admin/includes/image.edit.php looks like this:

apply_filters('wp_save_image_editor_file', null, $filename, $image, $mime_type, $post_id);

So a callback would look like the following:

add_filter( 'wp_save_image_editor_file', 'wpse91038_saved_image_editor_file', 10, 5 );
function wpse91038_saved_image_editor_file( $saved, $filename, $image, $mime_type, $post_id )
{
    var_dump( $saved );
    var_dump( $filename );
    var_dump( $image );
    var_dump( $mime_type );
    var_dump( $post_id );
    return $saved;
}

Right above the core filter, there’s another filter:

apply_filters('image_editor_save_pre', $image, $post_id);

The result of this filter, is then used as the 3rd argument inside the wp_save_image_editor_file-filter.

Then there’s another important thing to note: If your custom wp_save_image_editor_file callback/function returns anything that is not NULL, then the core function will abort:

if ( null !== $saved )
    return $saved;

return $image->save( $filename, $mime_type );

So you either do the $image->save( $filename, $mime_type ); inside your callback, or you will be left with an image that doesn’t get saved. And if you want to do so, then better don’t return the $saved with no value/NULL.

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