imageproc 0.27.0

Image processing operations
Documentation 
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#[cfg(feature = "rayon")]
use super::filter_clamped_parallel;
use super::{filter_clamped, gaussian_blur_f32};
use crate::{
    definitions::{Clamp, Image},
    kernel::Kernel,
    map::{map_pixels2, map_subpixels},
};
use image::{GrayImage, Luma};

/// Sharpens a grayscale image by applying a 3x3 approximation to the Laplacian.
#[must_use = "the function does not modify the original image"]
pub fn sharpen3x3(image: &GrayImage) -> GrayImage {
    let identity_minus_laplacian = Kernel::new(&[0, -1, 0, -1, 5, -1, 0, -1, 0], 3, 3);
    filter_clamped(image, identity_minus_laplacian)
}
#[must_use = "the function does not modify the original image"]
#[cfg(feature = "rayon")]
#[doc = generate_parallel_doc_comment!("sharpen3x3")]
pub fn sharpen3x3_parallel(image: &GrayImage) -> GrayImage {
    let identity_minus_laplacian = Kernel::new(&[0, -1, 0, -1, 5, -1, 0, -1, 0], 3, 3);
    filter_clamped_parallel(image, identity_minus_laplacian)
}

/// Sharpens a grayscale image using a Gaussian as a low-pass filter.
///
/// * `sigma` is the standard deviation of the Gaussian filter used.
/// * `amount` controls the level of sharpening. `output = input + amount * edges`.
// TODO: remove unnecessary allocations, support colour images
#[must_use = "the function does not modify the original image"]
pub fn sharpen_gaussian(image: &GrayImage, sigma: f32, amount: f32) -> GrayImage {
    let image = map_subpixels(image, |x| x as f32);
    let smooth: Image<Luma<f32>> = gaussian_blur_f32(&image, sigma);
    map_pixels2(&image, &smooth, |p, q| {
        let v = (1.0 + amount) * p[0] - amount * q[0];
        Luma([<u8 as Clamp<f32>>::clamp(v)])
    })
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    #[cfg(feature = "rayon")]
    fn test_sharpen3x3_parallel_matches_sharpen3x3() {
        let image = gray_image!(
            1, 2, 3;
            4, 5, 6;
            7, 8, 9);

        let expected = sharpen3x3(&image);
        let actual = sharpen3x3_parallel(&image);

        assert_pixels_eq!(actual, expected);
    }
}

#[cfg(not(miri))]
#[cfg(test)]
mod proptests {
    use super::*;
    use crate::proptest_utils::arbitrary_image;
    use proptest::prelude::*;

    proptest! {
        #[test]
        #[cfg(feature = "rayon")]
        fn proptest_sharpen3x3_parallel_matches_sharpen3x3(
            img in arbitrary_image::<Luma<u8>>(0..30, 0..30),
        ) {
            let expected = sharpen3x3(&img);
            let actual = sharpen3x3_parallel(&img);

            prop_assert_eq!(actual, expected);
        }
    }
}