imageproc/drawing/
polygon.rs

1use crate::definitions::Image;
2use crate::drawing::line::draw_line_segment_mut;
3use crate::drawing::Canvas;
4use crate::point::Point;
5use image::{GenericImage, ImageBuffer};
6use std::cmp::{max, min};
7use std::f32;
8use std::i32;
9
10/// Draws a polygon and its contents on a new copy of an image.
11///
12/// Draws as much of a filled polygon as lies within image bounds. The provided
13/// list of points should be an open path, i.e. the first and last points must not be equal.
14/// An implicit edge is added from the last to the first point in the slice.
15#[must_use = "the function does not modify the original image"]
16pub fn draw_polygon<I>(image: &I, poly: &[Point<i32>], color: I::Pixel) -> Image<I::Pixel>
17where
18    I: GenericImage,
19{
20    let mut out = ImageBuffer::new(image.width(), image.height());
21    out.copy_from(image, 0, 0).unwrap();
22    draw_polygon_mut(&mut out, poly, color);
23    out
24}
25
26/// Draws a polygon and its contents on an image in place.
27///
28/// Draws as much of a filled polygon as lies within image bounds. The provided
29/// list of points should be an open path, i.e. the first and last points must not be equal.
30/// An implicit edge is added from the last to the first point in the slice.
31pub fn draw_polygon_mut<C>(canvas: &mut C, poly: &[Point<i32>], color: C::Pixel)
32where
33    C: Canvas,
34{
35    if poly.is_empty() {
36        return;
37    }
38    if poly[0] == poly[poly.len() - 1] {
39        panic!(
40            "First point {:?} == last point {:?}",
41            poly[0],
42            poly[poly.len() - 1]
43        );
44    }
45
46    let mut y_min = i32::MAX;
47    let mut y_max = i32::MIN;
48    for p in poly {
49        y_min = min(y_min, p.y);
50        y_max = max(y_max, p.y);
51    }
52
53    let (width, height) = canvas.dimensions();
54
55    // Intersect polygon vertical range with image bounds
56    y_min = max(0, min(y_min, height as i32 - 1));
57    y_max = max(0, min(y_max, height as i32 - 1));
58
59    let mut closed: Vec<Point<i32>> = poly.to_vec();
60    closed.push(poly[0]);
61
62    let edges: Vec<&[Point<i32>]> = closed.windows(2).collect();
63    let mut intersections = Vec::new();
64
65    for y in y_min..y_max + 1 {
66        for edge in &edges {
67            let p0 = edge[0];
68            let p1 = edge[1];
69
70            if p0.y <= y && p1.y >= y || p1.y <= y && p0.y >= y {
71                if p0.y == p1.y {
72                    // Need to handle horizontal lines specially
73                    intersections.push(p0.x);
74                    intersections.push(p1.x);
75                } else if p0.y == y || p1.y == y {
76                    if p1.y > y {
77                        intersections.push(p0.x);
78                    }
79                    if p0.y > y {
80                        intersections.push(p1.x);
81                    }
82                } else {
83                    let fraction = (y - p0.y) as f32 / (p1.y - p0.y) as f32;
84                    let inter = p0.x as f32 + fraction * (p1.x - p0.x) as f32;
85                    intersections.push(inter.round() as i32);
86                }
87            }
88        }
89
90        intersections.sort_unstable();
91        intersections.chunks(2).for_each(|range| {
92            let mut from = min(range[0], width as i32);
93            let mut to = min(range[1], width as i32 - 1);
94            if from < width as i32 && to >= 0 {
95                // draw only if range appears on the canvas
96                from = max(0, from);
97                to = max(0, to);
98
99                for x in from..to + 1 {
100                    canvas.draw_pixel(x as u32, y as u32, color);
101                }
102            }
103        });
104
105        intersections.clear();
106    }
107
108    for edge in &edges {
109        let start = (edge[0].x as f32, edge[0].y as f32);
110        let end = (edge[1].x as f32, edge[1].y as f32);
111        draw_line_segment_mut(canvas, start, end, color);
112    }
113}
imageproc/drawing/polygon.rs

imageproc/drawing/
polygon.rs
