Wordpress - set custom image size in Media Library #wordpress

custom-image-size.php

/* Custom image sizes to Media Library */
function wp_70048_remove_image_sizes( $sizes ) {
	unset( $sizes['thumbnail'] );
	unset( $sizes['medium'] );
	unset( $sizes['large'] );
	unset( $sizes['full'] );

	return $sizes;
}

add_filter( 'image_size_names_choose', 'wp_70048_remove_image_sizes' );

add_filter( 'image_size_names_choose', 'my_image_sizes' );
function my_image_sizes( $sizes ) {
	$addsizes = array(
		"singleinside"   => __( "Inside Wide Image" ),
		"singlesixteen"  => __( "Inside Normal Image" ),
		"singleportrait" => __( "Inside Portrait Image" ),
		"medium"         => __( "Small Square Image" )
	);
	$newsizes = array_merge( $sizes, $addsizes );

	return $newsizes;
}