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 num_complex::Complex;

pub fn gaussian_kernel_1d(width: u32, sigma: f32) -> Vec<f32> {
    let mut sum_norm: f32 = 0.;
    let mut kernel: Vec<f32> = vec![0.; width as usize];
    let scale = 1f32 / (f32::sqrt(2. * std::f32::consts::PI) * sigma);
    let mean = (width / 2) as f32;

    for (x, item) in kernel.iter_mut().enumerate() {
        let dx = (x as f32 - mean) / sigma;
        let new_weight = f32::exp(-0.5 * dx * dx) * scale;
        *item = new_weight;
        sum_norm += new_weight;
    }

    if sum_norm != 0f32 {
        let sum_scale = 1f32 / sum_norm;
        for item in kernel.iter_mut() {
            *item *= sum_scale;
        }
    }

    kernel
}

pub fn gaussian_kernel_1d_f64(width: u32, sigma: f64) -> Vec<f64> {
    let mut sum_norm: f64 = 0.;
    let mut kernel: Vec<f64> = vec![0.; width as usize];
    let scale = 1. / (f64::sqrt(2. * std::f64::consts::PI) * sigma);
    let mean = (width / 2) as f64;

    for (x, item) in kernel.iter_mut().enumerate() {
        let dx = (x as f64 - mean) / sigma;
        let new_weight = f64::exp(-0.5 * dx * dx) * scale;
        *item = new_weight;
        sum_norm += new_weight;
    }

    if sum_norm != 0. {
        let sum_scale = 1. / sum_norm;
        for item in kernel.iter_mut() {
            *item *= sum_scale;
        }
    }

    kernel
}

/// Regular gaussian kernel with phase shift.
pub fn complex_gaussian_kernel(radius: f64, scale: f64, distortion: f64) -> Vec<Complex<f32>> {
    if radius < 1. {
        panic!("Radius cannot be less than 1");
    }
    let kernel_radius = radius.ceil() as usize;
    let mut kernel: Vec<Complex<f64>> = vec![Complex::new(0.0, 0.0); 1 + 2 * (kernel_radius)];

    for (x, dst) in kernel.iter_mut().enumerate() {
        let ax = (x as f64 - radius) * scale / radius;
        let ax2 = ax * ax;
        let exp_a = (-distortion * ax2).exp();
        let val = Complex::new(
            exp_a * (distortion * ax2).cos(),
            exp_a * (distortion * ax2).sin(),
        );
        *dst = val;
    }

    let sum: f64 = kernel.iter().map(|z| z.norm_sqr()).sum::<f64>();
    if sum != 0.0 {
        kernel
            .iter()
            .map(|z| Complex {
                re: (z.re / sum) as f32,
                im: (z.im / sum) as f32,
            })
            .collect::<Vec<_>>()
    } else {
        kernel
            .iter()
            .map(|x| Complex {
                re: x.re as f32,
                im: x.im as f32,
            })
            .collect()
    }
}