// in functions.php
if ( function_exists( 'add_image_size' ) ) {
        // set image size here
	add_image_size( 'homepage-thumb', 300, 9999 );
}

// in functions.php
if ( function_exists( 'add_image_size' ) ) {
        // set image size here
	add_image_size( 'homepage-thumb', 300, 9999 );
}