plotters_backend/rasterizer/
line.rs

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1use crate::{BackendCoord, BackendStyle, DrawingBackend, DrawingErrorKind};
2
3pub fn draw_line<DB: DrawingBackend, S: BackendStyle>(
4    back: &mut DB,
5    mut from: BackendCoord,
6    mut to: BackendCoord,
7    style: &S,
8) -> Result<(), DrawingErrorKind<DB::ErrorType>> {
9    if style.color().alpha == 0.0 || style.stroke_width() == 0 {
10        return Ok(());
11    }
12
13    if style.stroke_width() != 1 {
14        // If the line is wider than 1px, then we need to make it a polygon
15        let v = (i64::from(to.0 - from.0), i64::from(to.1 - from.1));
16        let l = ((v.0 * v.0 + v.1 * v.1) as f64).sqrt();
17
18        if l < 1e-5 {
19            return Ok(());
20        }
21
22        let v = (v.0 as f64 / l, v.1 as f64 / l);
23
24        let r = f64::from(style.stroke_width()) / 2.0;
25        let mut trans = [(v.1 * r, -v.0 * r), (-v.1 * r, v.0 * r)];
26        let mut vertices = vec![];
27
28        for point in [from, to].iter() {
29            for t in trans.iter() {
30                vertices.push((
31                    (f64::from(point.0) + t.0) as i32,
32                    (f64::from(point.1) + t.1) as i32,
33                ))
34            }
35
36            trans.swap(0, 1);
37        }
38
39        return back.fill_polygon(vertices, style);
40    }
41
42    if from.0 == to.0 {
43        if from.1 > to.1 {
44            std::mem::swap(&mut from, &mut to);
45        }
46        for y in from.1..=to.1 {
47            check_result!(back.draw_pixel((from.0, y), style.color()));
48        }
49        return Ok(());
50    }
51
52    if from.1 == to.1 {
53        if from.0 > to.0 {
54            std::mem::swap(&mut from, &mut to);
55        }
56        for x in from.0..=to.0 {
57            check_result!(back.draw_pixel((x, from.1), style.color()));
58        }
59        return Ok(());
60    }
61
62    let steep = (from.0 - to.0).abs() < (from.1 - to.1).abs();
63
64    if steep {
65        from = (from.1, from.0);
66        to = (to.1, to.0);
67    }
68
69    let (from, to) = if from.0 > to.0 {
70        (to, from)
71    } else {
72        (from, to)
73    };
74
75    let mut size_limit = back.get_size();
76
77    if steep {
78        size_limit = (size_limit.1, size_limit.0);
79    }
80
81    let grad = f64::from(to.1 - from.1) / f64::from(to.0 - from.0);
82
83    let mut put_pixel = |(x, y): BackendCoord, b: f64| {
84        if steep {
85            back.draw_pixel((y, x), style.color().mix(b))
86        } else {
87            back.draw_pixel((x, y), style.color().mix(b))
88        }
89    };
90
91    let y_step_limit =
92        (f64::from(to.1.min(size_limit.1 as i32 - 1).max(0) - from.1) / grad).floor() as i32;
93
94    let batch_start = (f64::from(from.1.min(size_limit.1 as i32 - 2).max(0) - from.1) / grad)
95        .abs()
96        .ceil() as i32
97        + from.0;
98
99    let batch_limit =
100        to.0.min(size_limit.0 as i32 - 2)
101            .min(from.0 + y_step_limit - 1);
102
103    let mut y = f64::from(from.1) + f64::from(batch_start - from.0) * grad;
104
105    for x in batch_start..=batch_limit {
106        check_result!(put_pixel((x, y as i32), 1.0 + y.floor() - y));
107        check_result!(put_pixel((x, y as i32 + 1), y - y.floor()));
108
109        y += grad;
110    }
111
112    if to.0 >= batch_limit + 1 && y < f64::from(to.1) {
113        let x = batch_limit as i32 + 1;
114        if 1.0 + y.floor() - y > 1e-5 {
115            check_result!(put_pixel((x, y as i32), 1.0 + y.floor() - y));
116        }
117        if y - y.floor() > 1e-5 && y + 1.0 < f64::from(to.1) {
118            check_result!(put_pixel((x, y as i32 + 1), y - y.floor()));
119        }
120    }
121
122    Ok(())
123}
plotters_backend/rasterizer/line.rs

plotters_backend/rasterizer/
line.rs
