How to disable generation of default image sizes for some custom post types?

Question

I used custom post type, where 'thumbnail', 'medium' and 'large' sized not required. I need to disable this sizes and create function or plugin, where i can set, which image size is required for each custom post type.

My first step is hooking of get_intermediate_image_sizes function from wp-includes/media.php. I have added this code to functions.php but it not working :(

add_filter('get_intermediate_image_sizes', 'get_intermediate_image_sizes_fixed');
function get_intermediate_image_sizes_fixed() {
    global $_wp_additional_image_sizes;
    //$image_sizes = array('thumbnail', 'medium', 'large'); // Standard sizes
    $image_sizes = array();
    if ( isset( $_wp_additional_image_sizes ) && count( $_wp_additional_image_sizes ) )
        $image_sizes = array_merge( $image_sizes, array_keys( $_wp_additional_image_sizes ) );
return apply_filters( 'intermediate_image_sizes', $image_sizes );
}   

UPD: Editing this line in media.php is working. Default types after changes not generating.

$image_sizes = array('thumbnail', 'medium', 'large');

But how to make work my hook?

Answer 1

I think the only solution you have at the moment is to disable all intermediate image sizes:

add_filter( 'intermediate_image_sizes', '__return_empty_array', 99 );

And then manually generate them, depending on the post type, by hooking into 'wp_generate_attachment_metadata', where you do have access to the attachment id (and therefore to it's parent post):

function do_your_stuff( $data, $attachment_id ) {
  // generate intermediate images

  return $data;
}

add_filter( 'wp_generate_attachment_metadata', 'do_your_stuff', 10, 2 );