Function filter2d 

pub fn filter2d<T, const CHANNELS: usize>(
    input: ImageView<'_, T, CHANNELS>,
    kernel: &Kernel2D,
    delta: f64,
    border: BorderMode<T, CHANNELS>,
) -> Result<Image<T, CHANNELS>, VisionError>
where
    T: PixelComponent,

Applies OpenCV-style correlation and converts the result back to the input dtype.