wordpress multiple post thumbnail hiding class attributes - php

Question

I'm using the multiple post thumbnails plugin for Wordpress and am trouble finding a way to remove the default html attributes wordpress seem to generate? When you view the html source it comes up with;
<img width="600" height="450" src="http://localhost/news/../media/news-specials/hotplate2thumb.jpg" class="attachment-post-thumbnail size-post-thumbnail" alt="hotplate2thumb" />
I want to remove the width and height because that's invalid code. And I want to remove the class too, to make the site look less wordpressy.
Ideally it should generate as:
<img src="http://localhost/news/../media/news-specials/hotplate2thumb.jpg" alt="hotplate2thumb" />
I've already got this in the functions.php
//remove class from the_post_thumbnail
function the_post_thumbnail_remove_class($output) {
$output = preg_replace('/class=".*?"/', '', $output);
return $output;
}
add_filter('post_thumbnail_html', 'the_post_thumbnail_remove_class');
add_filter( 'post_thumbnail_html', 'remove_width_attribute', 10 );
add_filter( 'image_send_to_editor', 'remove_width_attribute', 10 );
function remove_width_attribute( $html ) {
$html = preg_replace( '/(width|height)="\d*"\s/', "", $html );
return $html;
}
But that only works for wordpress' defult post thumbnails and not the multiple/secondary one.
I also tried implementing the code like so on the template:
<?php
if (class_exists('MultiPostThumbnails')):
echo "<img src=\"".MultiPostThumbnails::get_post_thumbnail_url(get_post_type(), 'secondary-image') . "\" alt=\"\" />";
endif; ?>
But that still renders a second image for all posts even if I don't have one set, so then I get broken images appearing in the theme. Not all my posts use a second image, only a few.
Thanks

Answer 1

Okay I solved it by adding
add_filter('post_secondary-image_thumbnail_html', 'the_post_thumbnail_remove_class');
add_filter( 'post_secondary-image_thumbnail_html', 'remove_width_attribute', 10 );
to this function
//remove class from the_post_thumbnail
function the_post_thumbnail_remove_class($output) {
$output = preg_replace('/class=".*?"/', '', $output);
return $output;
}
add_filter('post_thumbnail_html', 'the_post_thumbnail_remove_class');
add_filter('post_secondary-image_thumbnail_html', 'the_post_thumbnail_remove_class');
add_filter( 'post_secondary-image_thumbnail_html', 'remove_width_attribute', 10 );
add_filter( 'post_thumbnail_html', 'remove_width_attribute', 10 );
add_filter( 'image_send_to_editor', 'remove_width_attribute', 10 );
function remove_width_attribute( $html ) {
$html = preg_replace( '/(width|height)="\d*"\s/', "", $html );
return $html;
}