pic-scale 0.7.8

High performance image scaling
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::math::consts::ConstPI;
use crate::math::mla;
use crate::math::sinc::Trigonometry;
use num_traits::{AsPrimitive, Float, MulAdd, Signed};
use std::ops::{Add, Div, Mul};

pub(crate) fn hann<
    V: Copy + ConstPI + Mul<Output = V> + Div<Output = V> + Signed + Float + 'static + Trigonometry,
>(
    x: V,
) -> V
where
    f32: AsPrimitive<V>,
{
    let length = 2.0f32.as_();
    let size = length * 2f32.as_();
    let size_scale = 1f32.as_() / size;
    if x.abs() > length {
        return 0f32.as_();
    }
    let r = (x * size_scale).f_cospi();
    let r = r * r;
    r * size_scale
}

pub(crate) fn hamming<
    V: Copy
        + ConstPI
        + Mul<Output = V>
        + Div<Output = V>
        + Signed
        + Float
        + Add<Output = V>
        + 'static
        + Trigonometry
        + MulAdd<V, Output = V>,
>(
    x: V,
) -> V
where
    f32: AsPrimitive<V>,
{
    let x = x.abs();
    if x == 0f32.as_() {
        1f32.as_()
    } else if x >= 1f32.as_() {
        0f32.as_()
    } else {
        mla(0.46f32.as_(), x.f_cospi(), 0.54f32.as_())
    }
}

pub(crate) fn hanning<
    V: Copy
        + ConstPI
        + Mul<Output = V>
        + Div<Output = V>
        + Signed
        + Float
        + Add<Output = V>
        + 'static
        + Trigonometry
        + MulAdd<V, Output = V>,
>(
    x: V,
) -> V
where
    f32: AsPrimitive<V>,
{
    let x = x.abs();
    if x == 0.0f32.as_() {
        1.0f32.as_()
    } else if x >= 1.0f32.as_() {
        0.0f32.as_()
    } else {
        mla(0.5f32.as_(), x.f_cospi(), 0.5f32.as_())
    }
}