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
|
/*
* This file is subject to the terms of the GFX License. If a copy of
* the license was not distributed with this file, you can obtain one at:
*
* http://ugfx.org/license.html
*/
#include "../../gfx.h"
#if GFX_USE_GMISC
#if GMISC_NEED_HITTEST_POLY
/* This function is used by gmiscHittestPoly()
*
* This function projects the point c on an horizontal line to the right.
* If the projection cuts the segment formed by the points a and b,
* the function returns 1. If the point c is on the segment, the function
* returns 0. If they don't intersect, it returns 2.
*/
static char _pointCrossingSegment(const point *a, const point *b, const point *c) {
/* If both points are left from our point, it won't intersect */
if (a->x < c->x && b->x < c->x) {
return -1;
}
/* Check if there is a point above and a point below, else
* it won't intersect.
*/
if (c->y <= a->y && c->y >= b->y) {
coord_t crossProduct;
/* If the line is parallel */
if (a->y == b->y) {
/* Point on the segment */
if ((c->x >= a->x && c->x <= b->x) || (c->x <= a->x && c->x >= b->x)) {
return 0;
} else {
return -1;
}
}
/* If the point is on the same horizontal line as one of the segment point,
* allow to add the intersection once
*/
if (c->y == b->y) {
return -1;
}
/* Matrix cross product to find if the point is left or right from the segment*/
crossProduct = (b->x - a->x) * (c->y - a->y) - (b->y - a->y) * (c->x - a->x);
/* Point left of the segment */
if (crossProduct < 0) {
return 1;
}
/* Point on the segment */
if (crossProduct == 0) {
return 0;
}
}
return -1;
}
bool_t gmiscHittestPoly(const point *pntarray, unsigned cnt, const point *p) {
unsigned i = 0;
uint8_t nbrIntersection = 0;
int8_t crossResult;
// For each pair of points
for (i = 0; i < cnt-1; i++) {
/* Order the two points from top to bottom to simplify the function */
if (pntarray[i].y >= pntarray[i+1].y) {
crossResult = _pointCrossingSegment(&pntarray[i], &pntarray[i+1], p);
} else {
crossResult = _pointCrossingSegment(&pntarray[i+1], &pntarray[i], p);
}
/* Point on the edge of the polygon */
if (crossResult == 0) {
return TRUE;
}
/* Point crossing the polygon */
else if(crossResult == 1) {
nbrIntersection++;
}
}
/* Last pair of points, can't be done in the loops
* Same as before
*/
if (pntarray[cnt-1].y >= pntarray[0].y) {
crossResult = _pointCrossingSegment(&pntarray[cnt-1], &pntarray[0], p);
} else {
crossResult = _pointCrossingSegment(&pntarray[0], &pntarray[cnt-1], p);
}
if (crossResult == 0) {
return TRUE;
} else if(crossResult == 1) {
nbrIntersection++;
}
/* If we cross an even pair of segments, we are outside */
if (nbrIntersection % 2 == 0) {
return FALSE;
}
/* Else we are inside the polygon */
return TRUE;
}
#endif // GMISC_NEED_HITTEST_POLY
#endif // GFX_USE_GMISC
|
