Ability to edit Canonical for attachment.php

Hmm that would require a custom filter at this point, there is a filter called wpseo_canonical that you can use to do that.

Thanks for the response. How do I get the post url that the attachment is assigned to outside the loop since I will need to do this before the loop.

Alright, I got it to work but it is outputting the canonical <link > tag twice.

This is the code I used I just need to know what extra step(s) I need to take to keep it from duplicating

function attachment_wpseo_canonical ($can) {
 global $wp_query;
 $attachment_page_id = $wp_query->post->ID;
 $parent_post = get_post($attachment_page_id);
 $parent_post_id = $parent_post->post_parent;

 $parent_post_permalink = get_permalink($parent_post_id);
 echo "<link rel=\"canonical\" href=\"$parent_post_permalink\" />";
 }
 add_filter('wpseo_canonical','attachment_wpseo_canonical');

you need to do return instead of echo

oh and btw the code is wrong too, as it would now do this on all pages. It should be:

function wpseo_attachment_canonical_parent( $canonical ) {
	if ( is_attachment() ) {
		global $post;
		$attachment = get_post( $post->ID );
		$parent_post_id = $attachment->post_parent;
		$canonical = get_permalink( $parent_post_id );
	}
	return $canonical;
}
add_filter( 'wpseo_canonical', 'wpseo_attachment_canonical_parent' );

Awesome, that works perfectly. Thank you!

Glad it works, resolving topic.