WordPress at a glance
filter is not described

get_image_tag_class filter-hook . WP 2.6.0

Filters the value of the attachment's image tag class attribute.

Usage

add_filter( 'get_image_tag_class', 'filter_function_name_2945', 10, 4 );
function filter_function_name_2945( $class, $id, $align, $size ){
	// filter...

	return $class;
}
$class(string)
CSS class name or space-separated list of classes.
$id(int)
Attachment ID.
$align(string)
Part of the class name for aligning the image.
$size(string/array)
Size of image. Image size or array of width and height values (in that order).
Default: 'medium'

Where the hook is called

get_image_tag()
wp-includes/media.php 380
$class = apply_filters( 'get_image_tag_class', $class, $id, $align, $size );

Where the hook is used (in WP core)

Does not used.