Function imageproc::utils::significant_pixel_diff_summary

pub fn significant_pixel_diff_summary<I, J, F, P>(
    actual: &I, 
    expected: &J, 
    is_significant_diff: F
) -> Option<String> where
    P: Pixel,
    P::Subpixel: Debug,
    I: GenericImage<Pixel = P>,
    J: GenericImage<Pixel = P>,
    F: Fn((u32, u32, I::Pixel), (u32, u32, J::Pixel)) -> bool, 

Human readable description of some of the pixels that differ signifcantly (according to provided function) between left and right, or None if all pixels match.