opencv --检测直线、圆、矩形
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：
/* This is a standalone program. Pass an image name as a first parameter of the program.
Switch between standard and probabilistic Hough transform by changing "#if 1" to "#if 0" and back */
#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;
}
检测圆代码：
#include <cv.h>
#include <highgui.h>
#include <math.h>
int main(int argc, char** argv)
{
IplImage* img;
if( argc == 2 && (img=cvLoadImage(argv[1], 1))!= 0)
{
IplImage* gray = cvCreateImage( cvGetSize(img), 8, 1 );
CvMemStorage* storage = cvCreateMemStorage(0);
cvCvtColor( img, gray, CV_BGR2GRAY );
cvSmooth( gray, gray, CV_GAUSSIAN, 9, 9 ); // smooth it, otherwise a lot of false circles may be detected
CvSeq* circles = cvHoughCircles( gray, storage, CV_HOUGH_GRADIENT, 2, gray->height/4, 200, 100 );
int i;
for( i = 0; i < circles->total; i++ )
{
float* p = (float*)cvGetSeqElem( circles, i );
cvCircle( img, cvPoint(cvRound(p[0]),cvRound(p[1])), 3, CV_RGB(0,255,0), -1, 8, 0 );
cvCircle( img, cvPoint(cvRound(p[0]),cvRound(p[1])), cvRound(p[2]), CV_RGB(255,0,0), 3, 8, 0 );
}
cvNamedWindow( "circles", 1 );
cvShowImage( "circles", img );
}
return 0;
}
检测矩形代码：
/*在程序里找寻矩形*/#ifdef _CH_#pragma package <opencv>#endif #ifndef _EiC#include "cv.h"#include "highgui.h"#include <stdio.h>#include <math.h>#include <string.h>#endif int thresh = 50;IplImage* img = 0;IplImage* img0 = 0;CvMemStorage* storage = 0;CvPoint pt[4];const char* wndname = "Square Detection Demo"; // helper function:// finds a cosine of angle between vectors// from pt0->pt1 and from pt0->pt2 double angle( CvPoint* pt1, CvPoint* pt2, CvPoint* pt0 ){ double dx1 = pt1->x - pt0->x; double dy1 = pt1->y - pt0->y; double dx2 = pt2->x - pt0->x; double dy2 = pt2->y - pt0->y; return (dx1*dx2 + dy1*dy2)/sqrt((dx1*dx1 + dy1*dy1)*(dx2*dx2 + dy2*dy2) + 1e-10);} // returns sequence of squares detected on the image.// the sequence is stored in the specified memory storageCvSeq* findSquares4( IplImage* img, CvMemStorage* storage ){ CvSeq* contours; int i, c, l, N = 11; CvSize sz = cvSize( img->width & -2, img->height & -2 ); IplImage* timg = cvCloneImage( img ); // make a copy of input image IplImage* gray = cvCreateImage( sz, 8, 1 ); IplImage* pyr = cvCreateImage( cvSize(sz.width/2, sz.height/2), 8, 3 ); IplImage* tgray; CvSeq* result; double s, t; // create empty sequence that will contain points - // 4 points per square (the square's vertices) CvSeq* squares = cvCreateSeq( 0, sizeof(CvSeq), sizeof(CvPoint), storage ); // select the maximum ROI in the image // with the width and height divisible by 2 cvSetImageROI( timg, cvRect( 0, 0, sz.width, sz.height )); // down-scale and upscale the image to filter out the noise cvPyrDown( timg, pyr, 7 ); cvPyrUp( pyr, timg, 7 ); tgray = cvCreateImage( sz, 8, 1 ); // find squares in every color plane of the image for( c = 0; c < 3; c++ ) { // extract the c-th color plane cvSetImageCOI( timg, c+1 ); cvCopy( timg, tgray, 0 ); // try several threshold levels for( l = 0; l < N; l++ ) { // hack: use Canny instead of zero threshold level. // Canny helps to catch squares with gradient shading if( l == 0 ) { // apply Canny. Take the upper threshold from slider // and set the lower to 0 (which forces edges merging) cvCanny( tgray, gray, 0, thresh, 5 ); // dilate canny output to remove potential // holes between edge segments cvDilate( gray, gray, 0, 1 ); } else { // apply threshold if l!=0: // tgray(x,y) = gray(x,y) < (l+1)*255/N ? 255 : 0 cvThreshold( tgray, gray, (l+1)*255/N, 255, CV_THRESH_BINARY ); } // find contours and store them all as a list cvFindContours( gray, storage, &contours, sizeof(CvContour), CV_RETR_LIST, CV_CHAIN_APPROX_SIMPLE, cvPoint(0,0) ); // test each contour while( contours ) { // approximate contour with accuracy proportional // to the contour perimeter result = cvApproxPoly( contours, sizeof(CvContour), storage, CV_POLY_APPROX_DP, cvContourPerimeter(contours)*0.02, 0 ); // square contours should have 4 vertices after approximation // relatively large area (to filter out noisy contours) // and be convex. // Note: absolute value of an area is used because // area may be positive or negative - in accordance with the // contour orientation if( result->total == 4 && fabs(cvContourArea(result,CV_WHOLE_SEQ)) > 1000 && cvCheckContourConvexity(result) ) { s = 0; for( i = 0; i < 5; i++ ) { // find minimum angle between joint // edges (maximum of cosine) if( i >= 2 ) { t = fabs(angle( (CvPoint*)cvGetSeqElem( result, i ), (CvPoint*)cvGetSeqElem( result, i-2 ), (CvPoint*)cvGetSeqElem( result, i-1 ))); s = s > t ? s : t; } } // if cosines of all angles are small // (all angles are ~90 degree) then write quandrange // vertices to resultant sequence if( s < 0.3 ) for( i = 0; i < 4; i++ ) cvSeqPush( squares, (CvPoint*)cvGetSeqElem( result, i )); } // take the next contour contours = contours->h_next; } } } // release all the temporary images cvReleaseImage( &gray ); cvReleaseImage( &pyr ); cvReleaseImage( &tgray ); cvReleaseImage( &timg ); return squares;} // the function draws all the squares in the imagevoid drawSquares( IplImage* img, CvSeq* squares ){ CvSeqReader reader; IplImage* cpy = cvCloneImage( img ); int i; // initialize reader of the sequence cvStartReadSeq( squares, &reader, 0 ); // read 4 sequence elements at a time (all vertices of a square) for( i = 0; i < squares->total; i += 4 ) { CvPoint* rect = pt; int count = 4; // read 4 vertices memcpy( pt, reader.ptr, squares->elem_size ); CV_NEXT_SEQ_ELEM( squares->elem_size, reader ); memcpy( pt + 1, reader.ptr, squares->elem_size ); CV_NEXT_SEQ_ELEM( squares->elem_size, reader ); memcpy( pt + 2, reader.ptr, squares->elem_size ); CV_NEXT_SEQ_ELEM( squares->elem_size, reader ); memcpy( pt + 3, reader.ptr, squares->elem_size ); CV_NEXT_SEQ_ELEM( squares->elem_size, reader ); // draw the square as a closed polyline cvPolyLine( cpy, &rect, &count, 1, 1, CV_RGB(0,255,0), 3, CV_AA, 0 ); } // show the resultant image cvShowImage( wndname, cpy ); cvReleaseImage( &cpy );} void on_trackbar( int a ){ if( img ) drawSquares( img, findSquares4( img, storage ) );} char* names[] = { "pic1.png", "pic2.png", "pic3.png", "pic4.png", "pic5.png", "pic6.png", 0 }; int main(int argc, char** argv){ int i, c; // create memory storage that will contain all the dynamic data storage = cvCreateMemStorage(0); for( i = 0; names[i] != 0; i++ ) { // load i-th image img0 = cvLoadImage( names[i], 1 ); if( !img0 ) { printf("Couldn't load %s\n", names[i] ); continue; } img = cvCloneImage( img0 ); // create window and a trackbar (slider) with parent "image" and set callback // (the slider regulates upper threshold, passed to Canny edge detector) cvNamedWindow( wndname, 1 ); cvCreateTrackbar( "canny thresh", wndname, &thresh, 1000, on_trackbar ); // force the image processing on_trackbar(0); // wait for key. // Also the function cvWaitKey takes care of event processing c = cvWaitKey(0); // release both images cvReleaseImage( &img ); cvReleaseImage( &img0 ); // clear memory storage - reset free space position cvClearMemStorage( storage ); if( c == 27 ) break; } cvDestroyWindow( wndname ); return 0;} #ifdef _EiCmain(1,"squares.c");#endif