1 /*
2 * Copyright (C) 2011 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17 /* $Id: db_image_homography.h,v 1.2 2011/06/17 14:03:31 mbansal Exp $ */
18
19 #ifndef DB_IMAGE_HOMOGRAPHY
20 #define DB_IMAGE_HOMOGRAPHY
21
22
23
24 /*****************************************************************
25 * Lean and mean begins here *
26 *****************************************************************/
27
28 #include "db_framestitching.h"
29 /*!
30 * \defgroup LMImageHomography (LM) Image Homography Estimation (feature based)
31 */
32 /*\{*/
33 /*!
34 Solve for projective H such that xp~Hx. Prior normalization is not necessary,
35 although desirable for numerical conditioning
36 \param H image projective (out)
37 \param x1 image 1 point 1
38 \param x2 image 1 point 2
39 \param x3 image 1 point 3
40 \param x4 image 1 point 4
41 \param xp1 image 2 point 1
42 \param xp2 image 2 point 2
43 \param xp3 image 2 point 3
44 \param xp4 image 2 point 4
45 */
46 DB_API void db_StitchProjective2D_4Points(double H[9],
47 double x1[3],double x2[3],double x3[3],double x4[3],
48 double xp1[3],double xp2[3],double xp3[3],double xp4[3]);
49
50 /*!
51 Solve for affine H such that xp~Hx. Prior normalization is not necessary,
52 although desirable for numerical conditioning
53 \param H image projective (out)
54 \param x1 image 1 point 1
55 \param x2 image 1 point 2
56 \param x3 image 1 point 3
57 \param xp1 image 2 point 1
58 \param xp2 image 2 point 2
59 \param xp3 image 2 point 3
60 */
61 DB_API void db_StitchAffine2D_3Points(double H[9],
62 double x1[3],double x2[3],double x3[3],
63 double xp1[3],double xp2[3],double xp3[3]);
64
65 /*!
66 Solve for rotation R such that xp~Rx.
67 Image points have to be of unit norm for the least squares to be meaningful.
68 \param R image rotation (out)
69 \param x1 image 1 point 1
70 \param x2 image 1 point 2
71 \param xp1 image 2 point 1
72 \param xp2 image 2 point 2
73 */
db_StitchCameraRotation_2Points(double R[9],double x1[3],double x2[3],double xp1[3],double xp2[3])74 inline void db_StitchCameraRotation_2Points(double R[9],
75 /*Image points have to be of unit norm
76 for the least squares to be meaningful*/
77 double x1[3],double x2[3],
78 double xp1[3],double xp2[3])
79 {
80 double* x[2];
81 double* xp[2];
82 double scale,t[3];
83
84 x[0]=x1;
85 x[1]=x2;
86 xp[0]=xp1;
87 xp[1]=xp2;
88 db_StitchSimilarity3DRaw(&scale,R,t,xp,x,2,1,0,1,0);
89 }
90
91 /*!
92 Solve for a homography H generated by a rotation R with a common unknown focal length f, i.e.
93 H=diag(f,f,1)*R*diag(1/f,1/f,1) such that xp~Hx.
94 If signed_disambiguation is true, the points are
95 required to be in front of the camera. No specific normalization of the homogenous points
96 is required, although it could be desirable to keep x1,x2,xp1 and xp2 of reasonable magnitude.
97 If a solution is obtained the function returns 1, otherwise 0. If the focal length is desired
98 a valid pointer should be passed in f
99 */
100 DB_API int db_StitchRotationCommonFocalLength_3Points(double H[9],double x1[3],double x2[3],double x3[3],
101 double xp1[3],double xp2[3],double xp3[3],double *f=0,int signed_disambiguation=1);
102
103 /*!
104 Find scale, rotation and translation of the similarity that
105 takes the nr_points inhomogenous 2D points X to Xp,
106 i.e. for the homogenous equivalents
107 Xp and X we would have
108 \code
109 Xp~
110 [sR t]*X
111 [0 1]
112 \endcode
113 If orientation_preserving is true, R is restricted such that det(R)>0.
114 allow_scaling, allow_rotation and allow_translation allow s,R and t
115 to differ from 1,Identity and 0
116
117 Full similarity takes the following on 550MHz:
118 \code
119 0.9 microseconds with 2 points
120 1.0 microseconds with 3 points
121 1.1 microseconds with 4 points
122 1.3 microseconds with 5 points
123 1.4 microseconds with 6 points
124 1.7 microseconds with 10 points
125 9 microseconds with 100 points
126 130 microseconds with 1000 points
127 1.3 milliseconds with 10000 points
128 35 milliseconds with 100000 points
129 350 milliseconds with 1000000 points
130 \endcode
131
132 Without orientation_preserving:
133 \code
134 3 points is minimal for (s,R,t) (R,t)
135 2 points is minimal for (s,t) (s,R) (R)
136 1 point is minimal for (s) (t)
137 \endcode
138
139 With orientation_preserving:
140 \code
141 2 points is minimal for (s,R,t) (R,t) (s,t)
142 1 point is minimal for (s,R) (R) (s) (t)
143 \endcode
144 \param scale (out)
145 \param R 2D rotation (out)
146 \param t 2D translation (out)
147 \param Xp (nr_points x 2) pointer to array of image points
148 \param X (nr_points x 2 ) pointer to array of image points
149 \param nr_points number of points
150 \param orientation_preserving
151 \param allow_scaling compute scale (if 0, scale=1)
152 \param allow_rotation compute rotation (if 0, R=[I])
153 \param allow_translation compute translation (if 0 t = [0,0]')
154 */
155 DB_API void db_StitchSimilarity2DRaw(double *scale,double R[4],double t[2],
156 double **Xp,double **X,int nr_points,int orientation_preserving=1,
157 int allow_scaling=1,int allow_rotation=1,int allow_translation=1);
158 /*!
159 See db_StitchRotationCommonFocalLength_3Points().
160 \param H Image similarity transformation (out)
161 \param Xp (nr_points x 2) pointer to array of image points
162 \param X (nr_points x 2) pointer to array of image points
163 \param nr_points number of points
164 \param orientation_preserving
165 \param allow_scaling compute scale (if 0, scale=1)
166 \param allow_rotation compute rotation (if 0, R=[I])
167 \param allow_translation compute translation (if 0 t = [0,0]')
168 */
169 inline void db_StitchSimilarity2D(double H[9],double **Xp,double **X,int nr_points,int orientation_preserving=1,
170 int allow_scaling=1,int allow_rotation=1,int allow_translation=1)
171 {
172 double s,R[4],t[2];
173
174 db_StitchSimilarity2DRaw(&s,R,t,Xp,X,nr_points,orientation_preserving,
175 allow_scaling,allow_rotation,allow_translation);
176
177 H[0]=s*R[0]; H[1]=s*R[1]; H[2]=t[0];
178 H[3]=s*R[2]; H[4]=s*R[3]; H[5]=t[1];
179 db_Zero2(H+6);
180 H[8]=1.0;
181 }
182 /*\}*/
183 #endif /* DB_IMAGE_HOMOGRAPHY */
184