检测直线：cvHoughLines，cvHoughLines2
检测圆：cvHoughCircles
检测矩形：OpenCV中没有对应的函数，下面有段代码可以检测矩形，是通过先找直线，然后找到直线平行与垂直的四根线。
检测直线代码：
- /* 这是一个独立的程序。 传递图像名称作为程序的第一个参数.
- 通过将“#if 1”更改为“#if 0”并返回，在标准和概率霍夫变换之间切换 */
- #include <cv.h>
- #include <highgui.h>
- #include <math.h>
- int main(int argc, char** argv)
- {
- const char* filename = argc >= 2 ? argv[1] : "pic1.png";
- IplImage* src = cvLoadImage( filename, 0 );
- IplImage* dst;
- IplImage* color_dst;
- CvMemStorage* storage = cvCreateMemStorage(0);
- CvSeq* lines = 0;
- int i;
- if( !src )
- return -1;
- dst = cvCreateImage( cvGetSize(src), 8, 1 );
- color_dst = cvCreateImage( cvGetSize(src), 8, 3 );
- cvCanny( src, dst, 50, 200, 3 );
- cvCvtColor( dst, color_dst, CV_GRAY2BGR );
- #if 0
- lines = cvHoughLines2( dst, storage, CV_HOUGH_STANDARD, 1, CV_PI/180, 100, 0, 0 );
- for( i = 0; i < MIN(lines->total,100); i++ )
- {
- float* line = (float*)cvGetSeqElem(lines,i);
- float rho = line[0];
- float theta = line[1];
- CvPoint pt1, pt2;
- double a = cos(theta), b = sin(theta);
- double x0 = a*rho, y0 = b*rho;
- pt1.x = cvRound(x0 + 1000*(-b));
- pt1.y = cvRound(y0 + 1000*(a));
- pt2.x = cvRound(x0 - 1000*(-b));
- pt2.y = cvRound(y0 - 1000*(a));
- cvLine( color_dst, pt1, pt2, CV_RGB(255,0,0), 3, CV_AA, 0 );
- }
- #else
- lines = cvHoughLines2( dst, storage, CV_HOUGH_PROBABILISTIC, 1, CV_PI/180, 50, 50, 10 );
- for( i = 0; i < lines->total; i++ )
- {
- CvPoint* line = (CvPoint*)cvGetSeqElem(lines,i);
- cvLine( color_dst, line[0], line[1], CV_RGB(255,0,0), 3, CV_AA, 0 );
- }
- #endif
- cvNamedWindow( "Source", 1 );
- cvShowImage( "Source", src );
- cvNamedWindow( "Hough", 1 );
- cvShowImage( "Hough", color_dst );
- cvWaitKey(0);
- return 0;
- }
