resvg 0.49.0

An SVG rendering library.
Documentation 
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// Copyright 2020 the Resvg Authors
// SPDX-License-Identifier: Apache-2.0 OR MIT

use super::ImageRefMut;
use rgb::RGBA8;
use usvg::filter::MorphologyOperator;

/// Applies a morphology filter.
///
/// `src` pixels should have a **premultiplied alpha**.
///
/// # Allocations
///
/// This method will allocate a copy of the `src` image as a back buffer.
pub fn apply(operator: MorphologyOperator, rx: f32, ry: f32, src: ImageRefMut) {
    let width_max = src.width - 1;
    let height_max = src.height - 1;
    let rx = (rx.round() as u32).min(width_max);
    let ry = (ry.round() as u32).min(height_max);

    let mut buf = vec![RGBA8::default(); src.data.len()];
    let mut buf = ImageRefMut::new(src.width, src.height, &mut buf);
    let mut x: u32 = 0;
    let mut y: u32 = 0;
    for _ in src.data.iter() {
        let mut new_p = RGBA8::default();
        if operator == MorphologyOperator::Erode {
            new_p.r = 255;
            new_p.g = 255;
            new_p.b = 255;
            new_p.a = 255;
        }

        let x_range = x.saturating_sub(rx)..=(x + rx).min(width_max);
        let y_range = y.saturating_sub(ry)..=(y + ry).min(height_max);

        for ty in y_range {
            for tx in x_range.clone() {
                let p = src.pixel_at(tx, ty);
                if operator == MorphologyOperator::Erode {
                    new_p.r = p.r.min(new_p.r);
                    new_p.g = p.g.min(new_p.g);
                    new_p.b = p.b.min(new_p.b);
                    new_p.a = p.a.min(new_p.a);
                } else {
                    new_p.r = p.r.max(new_p.r);
                    new_p.g = p.g.max(new_p.g);
                    new_p.b = p.b.max(new_p.b);
                    new_p.a = p.a.max(new_p.a);
                }
            }
        }

        *buf.pixel_at_mut(x, y) = new_p;

        x += 1;
        if x == src.width {
            x = 0;
            y += 1;
        }
    }

    // Do not use `mem::swap` because `data` referenced via FFI.
    src.data.copy_from_slice(buf.data);
}