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
|
import * as LineUtil from './LineUtil';
/*
* @namespace PolyUtil
* Various utility functions for polygon geometries.
*/
/* @function clipPolygon(points: Point[], bounds: Bounds, round?: Boolean): Point[]
* Clips the polygon geometry defined by the given `points` by the given bounds (using the [Sutherland-Hodgman algorithm](https://en.wikipedia.org/wiki/Sutherland%E2%80%93Hodgman_algorithm)).
* Used by Leaflet to only show polygon points that are on the screen or near, increasing
* performance. Note that polygon points needs different algorithm for clipping
* than polyline, so there's a separate method for it.
*/
export function clipPolygon(points, bounds, round) {
var clippedPoints,
edges = [1, 4, 2, 8],
i, j, k,
a, b,
len, edge, p;
for (i = 0, len = points.length; i < len; i++) {
points[i]._code = LineUtil._getBitCode(points[i], bounds);
}
// for each edge (left, bottom, right, top)
for (k = 0; k < 4; k++) {
edge = edges[k];
clippedPoints = [];
for (i = 0, len = points.length, j = len - 1; i < len; j = i++) {
a = points[i];
b = points[j];
// if a is inside the clip window
if (!(a._code & edge)) {
// if b is outside the clip window (a->b goes out of screen)
if (b._code & edge) {
p = LineUtil._getEdgeIntersection(b, a, edge, bounds, round);
p._code = LineUtil._getBitCode(p, bounds);
clippedPoints.push(p);
}
clippedPoints.push(a);
// else if b is inside the clip window (a->b enters the screen)
} else if (!(b._code & edge)) {
p = LineUtil._getEdgeIntersection(b, a, edge, bounds, round);
p._code = LineUtil._getBitCode(p, bounds);
clippedPoints.push(p);
}
}
points = clippedPoints;
}
return points;
}
|
