Add image URL automatically to custom field?

Question

Does anyone know how I automatically add the URL of the uploaded image to a custom field?

In other words, When I upload a image I want the url to the image to get a custom field variable automatically so I dont have to add the URL manually to the custom field all the time.

I need a seamless integration to make is user-friendly. I want to use scripts like timthumb instead of the built in WP functionality.

-----UPDATE:

Here is some code I have. Just missing the thumbnail variable in the custom value field.

add_action('wp_insert_post', 'mk_set_default_custom_fields');

function mk_set_default_custom_fields($post_id)
{
    if ( $_GET['post_type'] != 'post' ) {

        add_post_meta($post_id, 'Image', 'I WANT THE THUMBNAIL HERE', true);

    }

    return true;
}

Answer 1

There's no need to store the URL in a custom field, the thumbnail id is already stored in a custom field under the key _thumbnail_id. You can fetch the ID via get_post_meta and use wp_get_attachment_image_src to get the URL.

Answer 2

Here is the final code that adds the thumbnail url to a custom field named Image.

function w_thumbnail_src() {
    if (has_post_thumbnail()) {
        $thumb = wp_get_attachment_image_src(get_post_thumbnail_id(), 'emphasis');
        return $thumb[0]; // thumbnail url
    } else {
        return '';  // or a default thumbnail url
    }
}


add_action('publish_page', 'add_custom_field_automatically', 'w_thumbnail_src');
add_action('publish_post', 'add_custom_field_automatically');
function add_custom_field_automatically($post_id) {
global $wpdb;
if(!wp_is_post_revision($post_id)) {
add_post_meta($post_id, 'Image', w_thumbnail_src(), true);
}
}