Function sobel_gradient_map

pub fn sobel_gradient_map<P, F, Q>(image: &Image<P>, f: F) -> Image<Q>
where
    P: Pixel<Subpixel = u8> + WithChannel<u16> + WithChannel<i16>,
    Q: Pixel,
    ChannelMap<P, u16>: HasBlack,
    F: Fn(ChannelMap<P, u16>) -> Q,

Computes per-channel gradients using Sobel filters and calls f to compute each output pixel.

Examples

use imageproc::gradients::{sobel_gradient_map};
use image::Luma;
use std::cmp;

// A shallow horizontal gradient in the red
// channel, a steeper vertical gradient in the
// blue channel, constant in the green channel.
let input = rgb_image!(
    [0, 5, 0], [1, 5, 0], [2, 5, 0];
    [0, 5, 2], [1, 5, 2], [2, 5, 2];
    [0, 5, 4], [1, 5, 4], [2, 5, 4]
);

// Computing independent per-channel gradients.
let channel_gradient = rgb_image!(type: u16,
    [ 4,  0,  8], [ 8,  0,  8], [ 4,  0,  8];
    [ 4,  0, 16], [ 8,  0, 16], [ 4,  0, 16];
    [ 4,  0,  8], [ 8,  0,  8], [ 4,  0,  8]
);

assert_pixels_eq!(
    sobel_gradient_map(&input, |p| p),
    channel_gradient
);

// Defining the gradient of an RGB image to be the
// mean of its per-channel gradients.
let mean_gradient = gray_image!(type: u16,
    4, 5, 4;
    6, 8, 6;
    4, 5, 4
);

assert_pixels_eq!(
    sobel_gradient_map(&input, |p| {
        let mean = (p[0] + p[1] + p[2]) / 3;
        Luma([mean])
    }),
    mean_gradient
);

// Defining the gradient of an RGB image to be the pixelwise
// maximum of its per-channel gradients.
let max_gradient = gray_image!(type: u16,
     8,  8,  8;
    16, 16, 16;
     8,  8,  8
);

assert_pixels_eq!(
    sobel_gradient_map(&input, |p| {
        let max = cmp::max(cmp::max(p[0], p[1]), p[2]);
        Luma([max])
    }),
    max_gradient
);