libblur 0.24.0

Fast image blurring in pure Rust
Documentation 
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/*
 * Copyright (c) Radzivon Bartoshyk. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without modification,
 * are permitted provided that the following conditions are met:
 *
 * 1.  Redistributions of source code must retain the above copyright notice, this
 * list of conditions and the following disclaimer.
 *
 * 2.  Redistributions in binary form must reproduce the above copyright notice,
 * this list of conditions and the following disclaimer in the documentation
 * and/or other materials provided with the distribution.
 *
 * 3.  Neither the name of the copyright holder nor the names of its
 * contributors may be used to endorse or promote products derived from
 * this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

use crate::{
    BlurError, BlurImage, BlurImageMut, EdgeMode2D, KernelShape, Scalar, ThreadingPolicy,
    filter_2d, sigma_size,
};

pub fn laplacian_kernel(size: usize) -> Vec<f32> {
    if size & 1 == 0 {
        panic!("Kernel size must be odd in 'get_laplacian_kernel'!");
    }
    let center_x = (size / 2) as f32;
    let center_y = (size / 2) as f32;
    let sigma = sigma_size(size as f32);

    let mut kernel = vec![f32::default(); size * size];

    let sigma_p_2 = sigma * sigma;

    let scale = -1. / (std::f32::consts::PI * sigma_p_2 * sigma_p_2);

    let mut sum = 0f32;

    for y in 0..size {
        for x in 0..size {
            let dx = x as f32 - center_x;
            let dy = y as f32 - center_y;
            let der = -((dx * dx + dy * dy) / (2. * sigma_p_2));
            let v = scale * (1. + der) * f32::exp(der);
            kernel[y * size + x] = v;
            sum += v;
        }
    }

    if sum != 0. {
        let scale = 1. / sum;

        for item in kernel.iter_mut() {
            *item *= scale;
        }
    }
    kernel
}

/// Performs laplacian of gaussian on the image
///
/// # Arguments
///
/// * `image`: Source image.
/// * `destination`: Destination image.
/// * `edge_modes`: Border handling mode see [EdgeMode] and [EdgeMode2D] for more info.
/// * `border_constant`: If [EdgeMode::Constant] border will be replaced with this provided [Scalar] value.
/// * `threading_policy`: see [ThreadingPolicy] for more info.
///
/// returns: ()
pub fn laplacian(
    image: &BlurImage<u8>,
    destination: &mut BlurImageMut<u8>,
    edge_modes: EdgeMode2D,
    border_constant: Scalar,
    threading_policy: ThreadingPolicy,
) -> Result<(), BlurError> {
    image.check_layout()?;
    destination.check_layout(Some(image))?;
    image.size_matches_mut(destination)?;
    let kernel = [-1, -1, -1, -1, 8, -1, -1, -1, -1];
    filter_2d::<u8, i16>(
        image,
        destination,
        &kernel,
        KernelShape::new(3, 3),
        edge_modes,
        border_constant,
        threading_policy,
    )
}