WordPress at a glance
filter is not described

image_add_caption_shortcode filter-hook . WP 2.6.0

Filters the image HTML markup including the caption shortcode.

Usage

add_filter( 'image_add_caption_shortcode', 'filter_function_name_8351', 10, 2 );
function filter_function_name_8351( $shcode, $html ){
	// filter...

	return $shcode;
}
$shcode(string)
The image HTML markup with caption shortcode.
$html(string)
The image HTML markup.

Where the hook is called

image_add_caption()
image_add_caption_shortcode
wp-admin/includes/media.php 230
return apply_filters( 'image_add_caption_shortcode', $shcode, $html );

Where the hook is used (in WP core)

Does not used.