opencv 查詢連通區域 最大面積例項
阿新 • • 發佈:2020-06-05
今天在弄一個查詢連通的最大面積的問題。
要把影象弄成黑底,白字,這樣才可以正確找到。
然後呼叫下邊的方法:
RETR_CCOMP:提取所有輪廓,並將輪廓組織成雙層結構(two-level hierarchy),頂層為連通域的外圍邊界,次層位內層邊界
#include <opencv2/imgproc.hpp> #include <opencv2/highgui.hpp> using namespace cv; using namespace std; int main( int argc,char** argv ) { Mat src = imread( argv[1] ); int largest_area=0; int largest_contour_index=0; Rect bounding_rect; Mat thr; cvtColor( src,thr,COLOR_BGR2GRAY ); //Convert to gray threshold( thr,125,255,THRESH_BINARY ); //Threshold the gray bitwise_not(thr,thr); //這裡先變反轉顏色 vector<vector<Point> > contours; // Vector for storing contours findContours( thr,contours,RETR_CCOMP,CHAIN_APPROX_SIMPLE ); // Find the contours in the image for( size_t i = 0; i< contours.size(); i++ ) // iterate through each contour. { double area = contourArea( contours[i] ); // Find the area of contour if( area > largest_area ) { largest_area = area; largest_contour_index = i; //Store the index of largest contour bounding_rect = boundingRect( contours[i] ); // Find the bounding rectangle for biggest contour } } drawContours( src,largest_contour_index,Scalar( 0,0 ),2 ); // Draw the largest contour using previously stored index. imshow( "result",src ); waitKey(); return 0; }
方法二: connectedComponentsWithStats
std::pair< int,int > MaxAreaFromSource(Mat srcImage,Mat &dstImage,int index) { /* vector<vector<cv::Point> > contours; // Vector for storing contours int largest_area=0; size_t largest_contour_index=0; Rect bounding_rect; findContours( srcImage,CHAIN_APPROX_SIMPLE ); // Find the contours in the image for( size_t i = 0; i< contours.size(); i++ ) // iterate through each contour. { double area = contourArea( contours[i] ); // Find the area of contour if( area > largest_area ) { largest_area = area; largest_contour_index = i; //Store the index of largest contour bounding_rect = boundingRect( contours[i] ); // Find the bounding rectangle for biggest contour } } Mat dst; cvtColor(srcImage,dst,CV_GRAY2RGB); drawContours( dst,2 ); // Draw the largest contour using previously stored index. imshow( "result",dst ); waitKey(); printf("%%%%%%%%%%%max area:%d\n",largest_area); return make_pair( largest_area,index); */ cv::Mat img_bool,labels,stats,centroids,img_color,img_gray; //連通域計算 int nccomps = cv::connectedComponentsWithStats ( srcImage,//二值影象 labels,//和原圖一樣大的標記圖 stats,//nccomps×5的矩陣 表示每個連通區域的外接矩形和麵積(pixel) centroids //nccomps×2的矩陣 表示每個連通區域的質心 ); //cv::imshow("labels",labels); //cv::waitKey(); vector<cv::Vec3b> colors(nccomps); colors[0] = cv::Vec3b(0,0); // background pixels remain black. printf( "index:%d==================\n",index ); vector< int >vec_width,vec_area,vec_height; for(int label = 1; label < nccomps; ++label) { colors[label] = cv::Vec3b( (std::rand()&255),(std::rand()&255),(std::rand()&255) ); std::cout << "Component "<< label << std::endl; std::cout << "CC_STAT_LEFT = " << stats.at<int>(label,cv::CC_STAT_LEFT) << std::endl; std::cout << "CC_STAT_TOP = " << stats.at<int>(label,cv::CC_STAT_TOP) << std::endl; std::cout << "CC_STAT_WIDTH = " << stats.at<int>(label,cv::CC_STAT_WIDTH) << std::endl; std::cout << "CC_STAT_HEIGHT = " << stats.at<int>(label,cv::CC_STAT_HEIGHT) << std::endl; std::cout << "CC_STAT_AREA = " << stats.at<int>(label,cv::CC_STAT_AREA) << std::endl; std::cout << "CENTER = (" << centroids.at<double>(label,0) <<","<< centroids.at<double>(label,1) << ")"<< std::endl << std::endl; int area = stats.at<int>(label,cv::CC_STAT_AREA); int left = stats.at<int>(label,cv::CC_STAT_LEFT); int top = stats.at<int>(label,cv::CC_STAT_TOP); int width = stats.at<int>(label,cv::CC_STAT_WIDTH); int height = stats.at<int>(label,cv::CC_STAT_HEIGHT); vec_area.push_back(area); vec_width.push_back(width); vec_height.push_back(height); } vector<int>::iterator bigwidth = std::max_element(std::begin(vec_width),std::end(vec_width)); vector<int>::iterator bigheight = std::max_element(std::begin(vec_height),std::end(vec_height)); vector<int>::iterator bigarea = std::max_element(std::begin(vec_area),std::end(vec_area)); //printf( "area:%d------------width:%d height:%d \n",*bigarea,*bigwidth,*bigheight ); //按照label值,對不同的連通域進行著色 img_color = cv::Mat::zeros(srcImage.size(),CV_8UC3); for( int y = 0; y < img_color.rows; y++ ) for( int x = 0; x < img_color.cols; x++ ) { int label = labels.at<int>(y,x); CV_Assert(0 <= label && label <= nccomps); img_color.at<cv::Vec3b>(y,x) = colors[label]; } cv::imshow("color",img_color); cv::waitKey(); return make_pair( *bigarea,index ); }
我先用這個函式實現了一下,效果正確,還是opencv demo 是正確的,網上找了個例子,害死我了。
說明一下:方法一 比 第二種方法 執行速度快很多哦! 這一點很重要。
以上這篇opencv 查詢連通區域 最大面積例項就是小編分享給大家的全部內容了,希望能給大家一個參考,也希望大家多多支援我們。