puny2d 0.0.2

Rusty 2d graphics software renderer library.
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308

// Imports
use crate::{
    math::{FloatExt,RangeExt},
    vector::{
        types::Coordinate,
        point::ORIGIN_POINT,
        path::{PathBase,FlatPath,FlatPathSegment}
    }
};
use std::{
    mem::replace as memory_replace,
    ops::Range,
    collections::{HashMap,BTreeMap}
};


// Path to scanlines
pub fn scanlines_from_path(path: &FlatPath, area_width: u16, area_height: u16) -> HashMap<u16,Vec<Range<u16>>> {
    // Scanlines buffer
    let mut scanlines = HashMap::with_capacity(1);
    struct ScanlineStop {
        x: Coordinate,
        winding: i8
    }
    // Path to lines
    let (mut last_point, mut last_move) = (&ORIGIN_POINT, &ORIGIN_POINT);
    path.segments().iter()
    .filter_map(|segment| match segment {
        FlatPathSegment::MoveTo(point) => {
            last_move = point;
            last_point = last_move;
            None
        }
        FlatPathSegment::Close => {
            let line = if last_point != last_move {Some( (last_point, last_move) )} else {None};
            last_move = &ORIGIN_POINT;
            last_point = last_move;
            line
        }
        FlatPathSegment::LineTo(point) =>
            Some((
                memory_replace(&mut last_point, point),
                point
            ))
    })
    // Discard unwanted lines
    .filter(|line|
        !line.0.y.eq_close(line.1.y)  && // Horizontal / zero-length
        !(line.0.y < 0.0 && line.1.y < 0.0) &&  // Top-outside
        !(line.0.y >= area_height as Coordinate && line.1.y >= area_height as Coordinate)   // Bottom-outside
    )
    // Generate scanlines
    .for_each(|line| {
        // Scan range
        let (mut cur_y, last_y) = (
            (line.0.y.min(line.1.y).round_half_down() + 0.5).max(0.5),
            (line.0.y.max(line.1.y).round_half_down() - 0.5).min(area_height as Coordinate - 0.5)
        );
        // Line direction as winding rule
        let winding = (line.1.y - line.0.y).signum() as i8;
        // Straight vertical line
        if line.0.x.eq_close(line.1.x) {
            while cur_y <= last_y {
                scanlines.entry(cur_y.floor() as u16).or_insert_with(|| Vec::with_capacity(2) ).push(ScanlineStop {
                    x: line.0.x,
                    winding
                });
                cur_y += 1.0;
            }
        }
        // Diagonal line
        else {
            let slope_x_by_y = {let line_vector = *line.1 - *line.0; line_vector.x / line_vector.y};
            while cur_y <= last_y {
                scanlines.entry(cur_y.floor() as u16).or_insert_with(|| Vec::with_capacity(2) ).push(ScanlineStop {
                    x: line.0.x + (cur_y - line.0.y) * slope_x_by_y,
                    winding
                });
                cur_y += 1.0;
            }
        }
    });
    // Convert scanline stops to ranges
    scanlines.into_iter()
    .map(|(row,mut scanline)| (
        row,
        {
            // Sort scanline stops
            scanline.sort_by(|stop1, stop2| stop1.x.partial_cmp(&stop2.x).expect("There isn't a NAN. Stop twitting me!") );
            // Pair & trim scanline stops to ranges
            let (mut coverage, mut range_start_option) = (0, None as Option<Coordinate>);
            scanline.into_iter()
            .filter_map(|stop| {
                let range = match range_start_option {
                    // Complete range
                    Some(range_start) if coverage + stop.winding as i16 == 0 => {
                        range_start_option = None;
                        Some(
                            FloatExt::clamp(range_start.round_half_down(), 0.0, area_width as Coordinate) as u16
                            ..
                            FloatExt::clamp(stop.x.round(), 0.0, area_width as Coordinate) as u16
                        )
                    }
                    // Save range start
                    None if coverage == 0 => {
                        range_start_option = Some(stop.x);
                        None
                    }
                    // Ignore over-coverage
                    _ => None
                };
                coverage += stop.winding as i16;
                range
            })
            // Discard empty scanline ranges
            .filter(|stop_range| !RangeExt::is_empty(stop_range) )
            // Return ranges
            .collect::<Vec<_>>()
        }
    ))
    // Discard empty scanlines after stops cleaning
    .filter(|(_,scanline)| !scanline.is_empty() )
    // Return optimized scanlines
    .collect()
}

// Merge scanlines from different samples and sort everything
pub fn merge_and_order_scanlines(mut scanlines_samples: Vec<HashMap<u16,Vec<Range<u16>>>>) -> BTreeMap<u16,Vec<Range<u16>>> {
    // Anything to do?
    if let Some((scanlines, other_scanlines_samples)) = scanlines_samples.split_first_mut() {
        // Merge all scanlines into first sample
        for (row, other_scanline_ranges) in other_scanlines_samples.iter_mut().flatten() {
            if let Some(scanline_ranges) = scanlines.get_mut(row) {
                scanline_ranges.append(other_scanline_ranges);
            } else {
                scanlines.insert(*row, other_scanline_ranges.drain(..).collect());
            }
        }
        // Convert scanlines to sorted map with sorted ranges
        scanlines.drain()
        .map(|mut scanline| {
            scanline.1.sort_by(|range1, range2| range1.start.cmp(&range2.start) );
            scanline
        })
        .collect::<BTreeMap<_,_>>()
    } else {
        BTreeMap::new()
    }
}


// Tests
#[cfg(test)]
mod tests {
    use crate::vector::{
        point::Point,
        path::{PathBase,FlatPath}
    };
    use super::{scanlines_from_path,HashMap,merge_and_order_scanlines};

    #[test]
    fn scanlines_unclosed() {
        // Path
        let mut path = FlatPath::default();
        path.move_to(Point {x: 1.0, y: 0.0})
            .line_to(Point {x: 1.0, y: 3.0})
            .line_to(Point {x: 4.0, y: 3.0});
        // Test
        assert_eq!(
            scanlines_from_path(&path, 4, 3),
            HashMap::new()
        );
    }

    #[test]
    fn scanlines_quad_trimmed() {
        // Path
        let mut path = FlatPath::default();
        path.move_to(Point {x: 1.0, y: 1.0})
            .line_to(Point {x: 6.0, y: 1.0})
            .line_to(Point {x: 6.0, y: 4.0})
            .line_to(Point {x: 1.0, y: 4.0})
            .close();
        // Test
        assert_eq!(
            scanlines_from_path(&path, 5, 5),
            [
                (1, vec![1..5]),
                (2, vec![1..5]),
                (3, vec![1..5])
            ].iter().cloned().collect()    // To map for comparison
        );
    }

    #[test]
    fn scanlines_hole() {
        // Path
        let mut path = FlatPath::default();
        path.move_to(Point {x: 0.0, y: 0.0})
            .line_to(Point {x: 9.0, y: 0.0})
            .line_to(Point {x: 9.0, y: 10.0})
            .line_to(Point {x: 0.0, y: 10.0})
            .close()
            .move_to(Point {x: 2.0, y: 2.0})
            .line_to(Point {x: 2.0, y: 5.0})
            .line_to(Point {x: 7.0, y: 5.0})
            .line_to(Point {x: 7.0, y: 2.0})
            .close();
        // Test
        assert_eq!(
            scanlines_from_path(&path, 10, 10),
            [
                (0, vec![0..9]),
                (1, vec![0..9]),
                (2, vec![0..2, 7..9]),
                (3, vec![0..2, 7..9]),
                (4, vec![0..2, 7..9]),
                (5, vec![0..9]),
                (6, vec![0..9]),
                (7, vec![0..9]),
                (8, vec![0..9]),
                (9, vec![0..9])
            ].iter().cloned().collect()    // To map for comparison
        );
    }

    #[test]
    fn scanlines_winding() {
        // Path
        let mut path = FlatPath::default();
        path.move_to(Point {x: 0.0, y: 0.0})
            .line_to(Point {x: 9.0, y: 0.0})
            .line_to(Point {x: 9.0, y: 10.0})
            .line_to(Point {x: 0.0, y: 10.0})
            .close()
            .move_to(Point {x: 2.0, y: 2.0})
            .line_to(Point {x: 7.0, y: 2.0})
            .line_to(Point {x: 7.0, y: 5.0})
            .line_to(Point {x: 2.0, y: 5.0})
            .close();
        // Test
        assert_eq!(
            scanlines_from_path(&path, 10, 10),
            [
                (0, vec![0..9]),
                (1, vec![0..9]),
                (2, vec![0..9]),
                (3, vec![0..9]),
                (4, vec![0..9]),
                (5, vec![0..9]),
                (6, vec![0..9]),
                (7, vec![0..9]),
                (8, vec![0..9]),
                (9, vec![0..9])
            ].iter().cloned().collect()    // To map for comparison
        );
    }

    #[test]
    fn scanlines_subpixels() {
        // Path
        let mut path = FlatPath::default();
        path.move_to(Point {x: 1.0, y: 1.0})
            .line_to(Point {x: 4.5, y: 1.0})
            .line_to(Point {x: 6.0, y: 1.7})
            .line_to(Point {x: 8.0, y: 1.0})
            .line_to(Point {x: 9.5, y: 1.0})
            .line_to(Point {x: 9.5, y: 7.0})
            .line_to(Point {x: 2.0, y: 7.0})
            .close();
        // Test
        assert_eq!(
            scanlines_from_path(&path, 10, 10),
            [
                (1, vec![1..6, 7..10]),
                (2, vec![1..10]),
                (3, vec![1..10]),
                (4, vec![2..10]),
                (5, vec![2..10]),
                (6, vec![2..10])
            ].iter().cloned().collect()    // To map for comparison
        );
    }

    #[test]
    fn scanlines_merge() {
        assert_eq!(
            merge_and_order_scanlines(vec![
                [
                    (0, vec![0..33]),
                    (1, vec![1..5]),
                    (3, vec![0..50, 4..7])
                ].iter().cloned().collect(),
                [
                    (1, vec![0..6]),
                    (2, vec![2..8]),
                    (3, vec![1..20, 1..3])
                ].iter().cloned().collect()
            ]),
            [
                (0, vec![0..33]),
                (1, vec![0..6, 1..5]),
                (2, vec![2..8]),
                (3, vec![0..50, 1..20, 1..3, 4..7])
            ].iter().cloned().collect()
        );
    }
}