1 /* GIMP - The GNU Image Manipulation Program
2  * Copyright (C) 1995 Spencer Kimball and Peter Mattis
3  *
4  * gimpcoords.c
5  * Copyright (C) 2002 Simon Budig  <simon@gimp.org>
6  *
7  * This program is free software: you can redistribute it and/or modify
8  * it under the terms of the GNU General Public License as published by
9  * the Free Software Foundation; either version 3 of the License, or
10  * (at your option) any later version.
11  *
12  * This program is distributed in the hope that it will be useful,
13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
15  * GNU General Public License for more details.
16  *
17  * You should have received a copy of the GNU General Public License
18  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
19  */
20 
21 #include "config.h"
22 
23 #include <glib-object.h>
24 
25 #include "libgimpmath/gimpmath.h"
26 
27 #include "core-types.h"
28 
29 #include "gimpcoords.h"
30 
31 
32 #define INPUT_RESOLUTION 256
33 
34 
35 /*   amul * a + bmul * b = ret_val  */
36 
37 void
gimp_coords_mix(const gdouble amul,const GimpCoords * a,const gdouble bmul,const GimpCoords * b,GimpCoords * ret_val)38 gimp_coords_mix (const gdouble     amul,
39                  const GimpCoords *a,
40                  const gdouble     bmul,
41                  const GimpCoords *b,
42                  GimpCoords       *ret_val)
43 {
44   if (b)
45     {
46       ret_val->x         = amul * a->x         + bmul * b->x;
47       ret_val->y         = amul * a->y         + bmul * b->y;
48       ret_val->pressure  = amul * a->pressure  + bmul * b->pressure;
49       ret_val->xtilt     = amul * a->xtilt     + bmul * b->xtilt;
50       ret_val->ytilt     = amul * a->ytilt     + bmul * b->ytilt;
51       ret_val->wheel     = amul * a->wheel     + bmul * b->wheel;
52       ret_val->velocity  = amul * a->velocity  + bmul * b->velocity;
53       ret_val->direction = amul * a->direction + bmul * b->direction;
54       ret_val->extended  = b->extended || a->extended;
55     }
56   else
57     {
58       ret_val->x         = amul * a->x;
59       ret_val->y         = amul * a->y;
60       ret_val->pressure  = amul * a->pressure;
61       ret_val->xtilt     = amul * a->xtilt;
62       ret_val->ytilt     = amul * a->ytilt;
63       ret_val->wheel     = amul * a->wheel;
64       ret_val->velocity  = amul * a->velocity;
65       ret_val->direction = amul * a->direction;
66       ret_val->extended  = a->extended;
67     }
68 }
69 
70 
71 /*    (a+b)/2 = ret_average  */
72 
73 void
gimp_coords_average(const GimpCoords * a,const GimpCoords * b,GimpCoords * ret_average)74 gimp_coords_average (const GimpCoords *a,
75                      const GimpCoords *b,
76                      GimpCoords       *ret_average)
77 {
78   gimp_coords_mix (0.5, a, 0.5, b, ret_average);
79 }
80 
81 
82 /* a + b = ret_add  */
83 
84 void
gimp_coords_add(const GimpCoords * a,const GimpCoords * b,GimpCoords * ret_add)85 gimp_coords_add (const GimpCoords *a,
86                  const GimpCoords *b,
87                  GimpCoords       *ret_add)
88 {
89   gimp_coords_mix (1.0, a, 1.0, b, ret_add);
90 }
91 
92 
93 /* a - b = ret_difference */
94 
95 void
gimp_coords_difference(const GimpCoords * a,const GimpCoords * b,GimpCoords * ret_difference)96 gimp_coords_difference (const GimpCoords *a,
97                         const GimpCoords *b,
98                         GimpCoords       *ret_difference)
99 {
100   gimp_coords_mix (1.0, a, -1.0, b, ret_difference);
101 }
102 
103 
104 /* a * f = ret_product  */
105 
106 void
gimp_coords_scale(const gdouble f,const GimpCoords * a,GimpCoords * ret_product)107 gimp_coords_scale (const gdouble     f,
108                    const GimpCoords *a,
109                    GimpCoords       *ret_product)
110 {
111   gimp_coords_mix (f, a, 0.0, NULL, ret_product);
112 }
113 
114 
115 /* local helper for measuring the scalarproduct of two gimpcoords. */
116 
117 gdouble
gimp_coords_scalarprod(const GimpCoords * a,const GimpCoords * b)118 gimp_coords_scalarprod (const GimpCoords *a,
119                         const GimpCoords *b)
120 {
121   return (a->x         * b->x        +
122           a->y         * b->y        +
123           a->pressure  * b->pressure +
124           a->xtilt     * b->xtilt    +
125           a->ytilt     * b->ytilt    +
126           a->wheel     * b->wheel    +
127           a->velocity  * b->velocity +
128           a->direction * b->direction);
129 }
130 
131 
132 /*
133  * The "length" of the gimpcoord.
134  * Applies a metric that increases the weight on the
135  * pressure/xtilt/ytilt/wheel to ensure proper interpolation
136  */
137 
138 gdouble
gimp_coords_length_squared(const GimpCoords * a)139 gimp_coords_length_squared (const GimpCoords *a)
140 {
141   GimpCoords upscaled_a;
142 
143   upscaled_a.x         = a->x;
144   upscaled_a.y         = a->y;
145   upscaled_a.pressure  = a->pressure  * INPUT_RESOLUTION;
146   upscaled_a.xtilt     = a->xtilt     * INPUT_RESOLUTION;
147   upscaled_a.ytilt     = a->ytilt     * INPUT_RESOLUTION;
148   upscaled_a.wheel     = a->wheel     * INPUT_RESOLUTION;
149   upscaled_a.velocity  = a->velocity  * INPUT_RESOLUTION;
150   upscaled_a.direction = a->direction * INPUT_RESOLUTION;
151 
152   return gimp_coords_scalarprod (&upscaled_a, &upscaled_a);
153 }
154 
155 
156 gdouble
gimp_coords_length(const GimpCoords * a)157 gimp_coords_length (const GimpCoords *a)
158 {
159   return sqrt (gimp_coords_length_squared (a));
160 }
161 
162 /*
163  * Distance via manhattan metric, an upper bound for the eucledian metric.
164  * used for e.g. bezier approximation
165  */
166 
167 gdouble
gimp_coords_manhattan_dist(const GimpCoords * a,const GimpCoords * b)168 gimp_coords_manhattan_dist (const GimpCoords *a,
169                             const GimpCoords *b)
170 {
171   gdouble dist = 0;
172 
173   dist += ABS (a->pressure - b->pressure);
174   dist += ABS (a->xtilt - b->xtilt);
175   dist += ABS (a->ytilt - b->ytilt);
176   dist += ABS (a->wheel - b->wheel);
177   dist += ABS (a->velocity - b->velocity);
178   dist += ABS (a->direction - b->direction);
179 
180   dist *= INPUT_RESOLUTION;
181 
182   dist += ABS (a->x - b->x);
183   dist += ABS (a->y - b->y);
184 
185   return dist;
186 }
187 
188 gboolean
gimp_coords_equal(const GimpCoords * a,const GimpCoords * b)189 gimp_coords_equal (const GimpCoords *a,
190                    const GimpCoords *b)
191 {
192   return (a->x         == b->x        &&
193           a->y         == b->y        &&
194           a->pressure  == b->pressure &&
195           a->xtilt     == b->xtilt    &&
196           a->ytilt     == b->ytilt    &&
197           a->wheel     == b->wheel    &&
198           a->velocity  == b->velocity &&
199           a->direction == b->direction);
200 
201   /* Extended attribute was omitted from this comparison deliberately,
202    * it describes the events origin, not its value
203    */
204 }
205 
206 /* helper for calculating direction of two gimpcoords. */
207 
208 gdouble
gimp_coords_direction(const GimpCoords * a,const GimpCoords * b)209 gimp_coords_direction (const GimpCoords *a,
210                        const GimpCoords *b)
211 {
212   gdouble direction;
213   gdouble delta_x, delta_y;
214 
215   delta_x = a->x - b->x;
216   delta_y = a->y - b->y;
217 
218   if ((delta_x == 0) && (delta_y == 0))
219     {
220       direction = a->direction;
221     }
222   else if (delta_x == 0)
223     {
224       if (delta_y > 0)
225         direction = 0.25;
226       else
227         direction = 0.75;
228     }
229   else if (delta_y == 0)
230     {
231       if (delta_x < 0)
232         direction = 0.0;
233       else
234         direction = 0.5;
235     }
236   else
237     {
238       direction = atan ((- 1.0 * delta_y) / delta_x) / (2 * G_PI);
239 
240       if (delta_x > 0.0)
241         direction = direction + 0.5;
242 
243       if (direction < 0.0)
244         direction = direction + 1.0;
245     }
246 
247   return direction;
248 }
249