WordPress at a glance
filter is not described

getimagesize_mimes_to_exts filter-hook . WP 3.0.0

Filters the list mapping image mime types to their respective extensions.

Usage

add_filter( 'getimagesize_mimes_to_exts', 'filter_function_name_6768' );
function filter_function_name_6768( $mime_to_ext ){
	// filter...

	return $mime_to_ext;
}
$mime_to_ext(array)
Array of image mime types and their matching extensions.

Where the hook is called

wp_check_filetype_and_ext()
wp-includes/functions.php 2317-2323
$mime_to_ext = apply_filters( 'getimagesize_mimes_to_exts', array(
	'image/jpeg' => 'jpg',
	'image/png'  => 'png',
	'image/gif'  => 'gif',
	'image/bmp'  => 'bmp',
	'image/tiff' => 'tif',
) );

Where the hook is used (in WP core)

Does not used.