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.
 */

pub fn fft_next_good_size(mut n: usize) -> usize {
    if n <= 2 {
        return 2;
    }

    loop {
        let mut m = n;

        // Divide by 2 until it's no longer divisible
        while m.is_multiple_of(2) {
            m /= 2;
        }

        // Divide by 3 until it's no longer divisible
        while m.is_multiple_of(3) {
            m /= 3;
        }

        // Divide by 5 until it's no longer divisible
        while m.is_multiple_of(5) {
            m /= 5;
        }

        // If m is reduced to 1, n is a good FFT size
        if m <= 1 {
            return n;
        }

        // Otherwise, increment n and try again
        n += 1;
    }
}

pub(crate) fn fft_next_good_size_real(mut n: usize) -> usize {
    if n <= 2 {
        return 2;
    }

    loop {
        let mut m = n;

        // Divide by 2 until it's no longer divisible
        while m.is_multiple_of(2) {
            m /= 2;
        }

        // Divide by 3 until it's no longer divisible
        while m.is_multiple_of(3) {
            m /= 3;
        }

        // Divide by 5 until it's no longer divisible
        while m.is_multiple_of(5) {
            m /= 5;
        }

        // Divide by 7 until it's no longer divisible
        while m.is_multiple_of(7) {
            m /= 7;
        }

        // If m is reduced to 1, n is a good FFT size
        if m <= 1 {
            return n;
        }

        // Otherwise, increment n and try again
        n += 1;
    }
}