*** UPDATE: Unfortunately, this method no longer works with the new media uploader introduced in WordPress 3.5 ***

Usually when an image thumbnail is inserted into a post, I would like the thumbnail to link to the large version of the image, not the full-size version. Often the original full-size version is straight from a user’s high-megapixel camera and takes a while to load, while the large version has been automatically downsized by WordPress according to its media settings and works beautifully with a lightbox plugin or script.

WordPress automatically creates a large version of the image, but unfortunately it does not support linking to the large version very easily at all from the Add Media window.

Thanks to this code from SergeyBiryukov, I created a simple plugin that adds the option to link to either the Full Size Image or the Large Image from the Add Media window:

Much better!

You may install the following plugin on WordPress 3.4.2 or drop it directly into the mu-plugins directory of your multisite installation: add-link-to-large-image.php

Here’s the code:

[fancy_code_box]

function add_link_to_large_image( $form_fields, $post ) {
$file = wp_get_attachment_url( $post->ID );
$link = get_attachment_link( $post->ID );

$url_type = get_option( ‘image_default_link_type’ );
if ( empty( $url_type ) )
$url_type = get_user_setting( ‘urlbutton’, ‘post’ );

$url = ”;
if ( $url_type == ‘file’ )
$url = $file;
elseif ( $url_type == ‘post’ )
$url = $link;

if ( substr( $post->post_mime_type, 0, 5 ) == ‘image’ ) {
$large_image_array = wp_get_attachment_image_src( $post->ID, ‘large’ );
$file_large = $large_image_array[0];
$url = $file_large;
}

$form_fields[‘url’][‘html’] = ”

” . __( ‘None’ ) . “
“;
if ( ! empty( $file_large ) )
$form_fields[‘url’][‘html’] .= ”
” . __( ‘Large Image’ ) . “
“;
$form_fields[‘url’][‘html’] .= ”
” . __( ‘File URL’ ) . “
” . __( ‘Attachment Post URL’ ) . “
“;

return $form_fields;
}
add_filter( ‘attachment_fields_to_edit’, ‘add_link_to_large_image’, 10, 2 );

[/fancy_code_box]