# include <opencv2/opencv.hpp> # include <opencv2/highgui.hpp> # include <opencv2/imgproc.hpp> # include <vector> using namespace cv; using namespace std ; * @brief 找出面积最大的轮廓, 保存在max_contour里 void find_max_area (InputArray contour) ; _InputArray max_contour; void find_max_area (InputArray contour) { static double area = -UINT_MAX; double now = contourArea(contour); if (now >= area) { area = now; max_contour = contour; int main ( int argc, const char * argv[]) { Mat barcode; Mat gray, grayX, grayY; Mat gradient; Mat blurred; Mat thresh, kernel, closed; vector < vector <Point>> contours; vector <Point> c; vector < vector <Point>> barcode_area; // 读取图像, 转为灰度图 barcode = imread( "barcode.jpg" ); if (!barcode.data) { fprintf ( stderr , "imread failed!\n" ); exit (EXIT_FAILURE); cvtColor(barcode, gray, COLOR_BGR2GRAY); // 分别计算X, Y方向上的梯度 Sobel(gray, grayX, CV_32F, 1 , 0 , -1 ); Sobel(gray, grayY, CV_32F, 0 , 1 , -1 ); // 从X中减去Y subtract(grayX, grayY, gradient); convertScaleAbs(gradient, gradient); // 模糊 blur(gradient, blurred, Size_< int >( 9 , 9 )); // 主要留下白色 threshold(blurred, thresh, 225 , 255 , THRESH_BINARY); // 建立闭区域 kernel = getStructuringElement(MORPH_RECT, Size_< int >( 21 , 7 )); morphologyEx(thresh, closed, MORPH_CLOSE, kernel); // 腐蚀并扩大范围 erode(closed, closed, NULL , Point( -1 , -1 ), 4 ); dilate(closed, closed, NULL , Point( -1 , -1 ), 4 ); // 查找轮廓 findContours(closed, contours, RETR_EXTERNAL, CHAIN_APPROX_SIMPLE); // 找出最大的那个 for_each(contours.begin(), contours.end(), find_max_area); // 取rect RotatedRect rect = minAreaRect(max_contour); vector < vector <Point> > barcode_area; Point2f vertices[ 4 ]; vector <Point> c1; rect.points(vertices); c1.push_back(vertices[ 0 ]); c1.push_back(vertices[ 1 ]); c1.push_back(vertices[ 2 ]); c1.push_back(vertices[ 3 ]); barcode_area.push_back(c1); // 在barcode上画出轮廓 drawContours(barcode, barcode_area, -1 , Scalar( 0 , 255 , 0 ), 3 ); // 在Window中显示 namedWindow( "Barcode" , CV_WINDOW_AUTOSIZE); imshow( "Barcode" , barcode); waitKey( 0 ); return 0 ;