Function box_blur 

pub fn box_blur<T, const CHANNELS: usize>(
    input: ImageView<'_, T, CHANNELS>,
    kernel_width: usize,
    kernel_height: usize,
    border: BorderMode<T, CHANNELS>,
) -> Result<Image<T, CHANNELS>, VisionError>
where
    T: PixelComponent,

Applies a normalized rectangular box filter.