fn compare_to_truth_image<P>(actual: &Image<P>, truth_file_name: &str)
where
    P: Pixel<Subpixel = u8> + PixelWithColorType,
    Image<P>: FromDynamic,
{
    compare_to_truth_image_with_tolerance(actual, truth_file_name, 0u8);
}
Checks that an image matches a 'truth' image.
tests/regression.rs