Add filter on certain thumbnail sizes only

Question

How to run this filter only on some specific registered thumbnail sizes '$size' ? like 'large' , 'medium' ....

add_filter( 'wp_get_attachment_image_attributes', 'wpse8170_add_lazyload_to_attachment_image', 10, 2 );
function wpse8170_add_lazyload_to_attachment_image( $attr, $attachment ) {
$attr['data-original'] = $attr['src'];
$attr['src'] = 'grey.gif';
return $attr;
}

Thanks

Answer 1

This is a hack, but I guess it should work...

add_filter( 'wp_get_attachment_image_attributes', 'wpse8170_add_lazyload_to_attachment_image', 10, 2 );
function wpse8170_add_lazyload_to_attachment_image( $attr, $attachment ) {
    //use your image size here with attachment
    if($attr['class'] == 'attachment-large'){
        //do your stuff
    }
    return $attr;
}