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<?php

/**
 * Remove standard image sizes so that these sizes are not created during the Media Upload process
 *
 * @param $sizes, array of default images
 * @return $sizes, new array of images
 */
function cn_image_sizes( $sizes) {
		
	unset( $sizes['thumbnail']);
	unset( $sizes['medium']);
	unset( $sizes['large']);
	
	return $sizes;
}
add_filter('intermediate_image_sizes_advanced', 'cn_image_sizes');

?>