pic-scale 0.7.5

High performance image scaling
Documentation 
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/*
 * Copyright (c) Radzivon Bartoshyk 3/2026. 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::convolution::ColumnFilter;
use crate::filter_weights::{FilterBounds, FilterWeights};
use crate::{ImageSize, ImageStore, ImageStoreMut, ThreadingPolicy};
use novtb::{ParallelZonedIterator, TbSliceMut};

pub(crate) struct VerticalFiltering<T, F, const N: usize> {
    pub(crate) filter_row: fn(usize, &FilterBounds, &[T], &mut [T], usize, &[F], u32),
    pub(crate) filter_weights: FilterWeights<F>,
    pub(crate) threading_policy: ThreadingPolicy,
}

impl<T: Send + Sync, F: Send + Sync, const N: usize> ColumnFilter<T, N>
    for VerticalFiltering<T, F, N>
where
    [T]: ToOwned<Owned = Vec<T>>,
{
    fn filter(&self, source: &ImageStore<'_, T, N>, destination: &mut ImageStoreMut<T, N>) {
        let pool = self
            .threading_policy
            .get_nova_pool(ImageSize::new(destination.width, destination.height));
        let src_stride = source.stride();
        let dst_stride = destination.stride();

        let dst_width = destination.width;

        let row_filter = self.filter_row;

        let dst_bit_depth = destination.bit_depth as u32;
        let dst_buffer = destination.projected();

        let source_buffer = source.projected();

        dst_buffer
            .tb_par_chunks_mut(dst_stride)
            .for_each_enumerated(&pool, |y, row| {
                if row.is_empty() {
                    return;
                }
                let bounds = self.filter_weights.bounds[y];
                let filter_offset = y * self.filter_weights.aligned_size;
                let weights = &self.filter_weights.weights[filter_offset..];
                row_filter(
                    dst_width,
                    &bounds,
                    source_buffer,
                    &mut row[..dst_width * N],
                    src_stride,
                    weights,
                    dst_bit_depth,
                );
            });
    }

    fn run_on_row(
        &self,
        src: &[T],
        dst: &mut [T],
        dst_width: usize,
        src_stride: usize,
        y: usize,
        bit_depth: u32,
    ) {
        let bounds = self.filter_weights.bounds[y];
        let filter_offset = y * self.filter_weights.aligned_size;
        let weights = &self.filter_weights.weights[filter_offset..];
        let row_filter = self.filter_row;
        row_filter(
            dst_width,
            &bounds,
            src,
            &mut dst[..dst_width * N],
            src_stride,
            weights,
            bit_depth,
        );
    }
}