1 /* Copyright (C) 2001-2017 Peter Selinger.
2 This file is part of Potrace. It is free software and it is covered
3 by the GNU General Public License. See the file COPYING for details. */
4
5 /* calculations with coordinate transformations and bounding boxes */
6
7 #ifdef HAVE_CONFIG_H
8 #include <config.h>
9 #endif
10
11 #include <math.h>
12 #include <string.h>
13
14 #include "trans.h"
15 #include "bbox.h"
16
17 /* rotate the coordinate system counterclockwise by alpha degrees. The
18 new bounding box will be the smallest box containing the rotated
19 old bounding box */
trans_rotate(trans_t * r,double alpha)20 void trans_rotate(trans_t *r, double alpha) {
21 double s, c, x0, x1, y0, y1, o0, o1;
22 trans_t t_struct;
23 trans_t *t = &t_struct;
24
25 memcpy(t, r, sizeof(trans_t));
26
27 s = sin(alpha/180*M_PI);
28 c = cos(alpha/180*M_PI);
29
30 /* apply the transformation matrix to the sides of the bounding box */
31 x0 = c * t->bb[0];
32 x1 = s * t->bb[0];
33 y0 = -s * t->bb[1];
34 y1 = c * t->bb[1];
35
36 /* determine new bounding box, and origin of old bb within new bb */
37 r->bb[0] = fabs(x0) + fabs(y0);
38 r->bb[1] = fabs(x1) + fabs(y1);
39 o0 = - min(x0,0) - min(y0,0);
40 o1 = - min(x1,0) - min(y1,0);
41
42 r->orig[0] = o0 + c * t->orig[0] - s * t->orig[1];
43 r->orig[1] = o1 + s * t->orig[0] + c * t->orig[1];
44 r->x[0] = c * t->x[0] - s * t->x[1];
45 r->x[1] = s * t->x[0] + c * t->x[1];
46 r->y[0] = c * t->y[0] - s * t->y[1];
47 r->y[1] = s * t->y[0] + c * t->y[1];
48 }
49
50 /* return the standard cartesian coordinate system for an w x h rectangle. */
trans_from_rect(trans_t * r,double w,double h)51 void trans_from_rect(trans_t *r, double w, double h) {
52 r->bb[0] = w;
53 r->bb[1] = h;
54 r->orig[0] = 0.0;
55 r->orig[1] = 0.0;
56 r->x[0] = 1.0;
57 r->x[1] = 0.0;
58 r->y[0] = 0.0;
59 r->y[1] = 1.0;
60 r->scalex = 1.0;
61 r->scaley = 1.0;
62 }
63
64 /* rescale the coordinate system r by factor sc >= 0. */
trans_rescale(trans_t * r,double sc)65 void trans_rescale(trans_t *r, double sc) {
66 r->bb[0] *= sc;
67 r->bb[1] *= sc;
68 r->orig[0] *= sc;
69 r->orig[1] *= sc;
70 r->x[0] *= sc;
71 r->x[1] *= sc;
72 r->y[0] *= sc;
73 r->y[1] *= sc;
74 r->scalex *= sc;
75 r->scaley *= sc;
76 }
77
78 /* rescale the coordinate system to size w x h */
trans_scale_to_size(trans_t * r,double w,double h)79 void trans_scale_to_size(trans_t *r, double w, double h) {
80 double xsc = w/r->bb[0];
81 double ysc = h/r->bb[1];
82
83 r->bb[0] = w;
84 r->bb[1] = h;
85 r->orig[0] *= xsc;
86 r->orig[1] *= ysc;
87 r->x[0] *= xsc;
88 r->x[1] *= ysc;
89 r->y[0] *= xsc;
90 r->y[1] *= ysc;
91 r->scalex *= xsc;
92 r->scaley *= ysc;
93
94 if (w<0) {
95 r->orig[0] -= w;
96 r->bb[0] = -w;
97 }
98 if (h<0) {
99 r->orig[1] -= h;
100 r->bb[1] = -h;
101 }
102 }
103
104 /* adjust the bounding box to the actual vector outline */
trans_tighten(trans_t * r,potrace_path_t * plist)105 void trans_tighten(trans_t *r, potrace_path_t *plist) {
106 interval_t i;
107 dpoint_t dir;
108 int j;
109
110 /* if pathlist is empty, do nothing */
111 if (!plist) {
112 return;
113 }
114
115 for (j=0; j<2; j++) {
116 dir.x = r->x[j];
117 dir.y = r->y[j];
118 path_limits(plist, dir, &i);
119 if (i.min == i.max) {
120 /* make the extent non-zero to avoid later division by zero errors */
121 i.max = i.min+0.5;
122 i.min = i.min-0.5;
123 }
124 r->bb[j] = i.max - i.min;
125 r->orig[j] = -i.min;
126 }
127 }
128