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42#include "precomp.hpp"
43
44void cv::cornerSubPix( InputArray _image, InputOutputArray _corners,
45 Size win, Size zeroZone, TermCriteria criteria )
46{
47 CV_INSTRUMENT_REGION();
48
49 const int MAX_ITERS = 100;
50 int win_w = win.width * 2 + 1, win_h = win.height * 2 + 1;
51 int i, j, k;
52 int max_iters = (criteria.type & TermCriteria::MAX_ITER) ? MIN(MAX(criteria.maxCount, 1), MAX_ITERS) : MAX_ITERS;
53 double eps = (criteria.type & TermCriteria::EPS) ? MAX(criteria.epsilon, 0.) : 0;
54 eps *= eps; // use square of error in comparison operations
55
56 cv::Mat src = _image.getMat(), cornersmat = _corners.getMat();
57 int count = cornersmat.checkVector(elemChannels: 2, CV_32F);
58 CV_Assert( count >= 0 );
59 Point2f* corners = cornersmat.ptr<Point2f>();
60
61 if( count == 0 )
62 return;
63
64 CV_Assert( win.width > 0 && win.height > 0 );
65 CV_Assert( src.cols >= win.width*2 + 5 && src.rows >= win.height*2 + 5 );
66 CV_Assert( src.channels() == 1 );
67
68 Mat maskm(win_h, win_w, CV_32F), subpix_buf(win_h+2, win_w+2, CV_32F);
69 float* mask = maskm.ptr<float>();
70
71 for( i = 0; i < win_h; i++ )
72 {
73 float y = (float)(i - win.height)/win.height;
74 float vy = std::exp(x: -y*y);
75 for( j = 0; j < win_w; j++ )
76 {
77 float x = (float)(j - win.width)/win.width;
78 mask[i * win_w + j] = (float)(vy*std::exp(x: -x*x));
79 }
80 }
81
82 // make zero_zone
83 if( zeroZone.width >= 0 && zeroZone.height >= 0 &&
84 zeroZone.width * 2 + 1 < win_w && zeroZone.height * 2 + 1 < win_h )
85 {
86 for( i = win.height - zeroZone.height; i <= win.height + zeroZone.height; i++ )
87 {
88 for( j = win.width - zeroZone.width; j <= win.width + zeroZone.width; j++ )
89 {
90 mask[i * win_w + j] = 0;
91 }
92 }
93 }
94
95 // do optimization loop for all the points
96 for( int pt_i = 0; pt_i < count; pt_i++ )
97 {
98 Point2f cT = corners[pt_i], cI = cT;
99 CV_Assert( Rect(0, 0, src.cols, src.rows).contains(cT) );
100 int iter = 0;
101 double err = 0;
102
103 do
104 {
105 Point2f cI2;
106 double a = 0, b = 0, c = 0, bb1 = 0, bb2 = 0;
107
108 getRectSubPix(image: src, patchSize: Size(win_w+2, win_h+2), center: cI, patch: subpix_buf, patchType: subpix_buf.type());
109 const float* subpix = &subpix_buf.at<float>(i0: 1,i1: 1);
110
111 // process gradient
112 for( i = 0, k = 0; i < win_h; i++, subpix += win_w + 2 )
113 {
114 double py = i - win.height;
115
116 for( j = 0; j < win_w; j++, k++ )
117 {
118 double m = mask[k];
119 double tgx = subpix[j+1] - subpix[j-1];
120 double tgy = subpix[j+win_w+2] - subpix[j-win_w-2];
121 double gxx = tgx * tgx * m;
122 double gxy = tgx * tgy * m;
123 double gyy = tgy * tgy * m;
124 double px = j - win.width;
125
126 a += gxx;
127 b += gxy;
128 c += gyy;
129
130 bb1 += gxx * px + gxy * py;
131 bb2 += gxy * px + gyy * py;
132 }
133 }
134
135 double det=a*c-b*b;
136 if( fabs( x: det ) <= DBL_EPSILON*DBL_EPSILON )
137 break;
138
139 // 2x2 matrix inversion
140 double scale=1.0/det;
141 cI2.x = (float)(cI.x + c*scale*bb1 - b*scale*bb2);
142 cI2.y = (float)(cI.y - b*scale*bb1 + a*scale*bb2);
143 err = (cI2.x - cI.x) * (cI2.x - cI.x) + (cI2.y - cI.y) * (cI2.y - cI.y);
144 // if new point is out of image, leave previous point as the result
145 if( !Rect(0, 0, src.cols, src.rows).contains(pt: cI2) )
146 break;
147 cI = cI2;
148 }
149 while( ++iter < max_iters && err > eps );
150
151 // if new point is too far from initial, it means poor convergence.
152 // leave initial point as the result
153 if( fabs( x: cI.x - cT.x ) > win.width || fabs( x: cI.y - cT.y ) > win.height )
154 cI = cT;
155
156 corners[pt_i] = cI;
157 }
158}
159
160
161CV_IMPL void
162cvFindCornerSubPix( const void* srcarr, CvPoint2D32f* _corners,
163 int count, CvSize win, CvSize zeroZone,
164 CvTermCriteria criteria )
165{
166 if(!_corners || count <= 0)
167 return;
168
169 cv::Mat src = cv::cvarrToMat(arr: srcarr), corners(count, 1, CV_32FC2, _corners);
170 cv::cornerSubPix(image: src, corners: corners, win, zeroZone, criteria);
171}
172
173/* End of file. */
174

source code of opencv/modules/imgproc/src/cornersubpix.cpp