WordPress at a glance
filter is not described

image_editor_default_mime_type filter-hook . WP 3.5.0

Filters default mime type prior to getting the file extension.

Usage

add_filter( 'image_editor_default_mime_type', 'filter_function_name_822' );
function filter_function_name_822( $mime_type ){
	// filter...

	return $mime_type;
}
$mime_type(string)
Mime type string.

Where the hook is called

WP_Image_Editor::get_output_format()
image_editor_default_mime_type
wp-includes/class-wp-image-editor.php 329
$mime_type = apply_filters( 'image_editor_default_mime_type', $this->default_mime_type );

Where the hook is used (in WP core)

Does not used.