cvFindContours/findContours提取轮廓

opencv在提取轮廓时，C/C++有两种方式，有些许不同，结合查找的资料和补充，做个小笔记；

功能，提取满足一定面积阈值和宽高比例的轮廓；

主函数

static int getContoursByC(char* Imgname, double minarea = 100, double whRatio = 1);
static int getContoursByCplus(char* Imgname, double minarea=0, double whRatio=1);
int main()
{
	char* filename = new char[50];
	strcpy(filename, "../image/rl_4.jpg");
	getContoursByCplus(filename);
	delete[] filename;
	return 0;
}

API实现

cvFindContours形式

/*采用cvFindContours提取轮廓，并过滤掉小面积轮廓，最后将轮廓保存*/
static int getContoursByC(char* Imgname, double minarea, double whRatio)
{
	IplImage* src = cvLoadImage(Imgname, CV_LOAD_IMAGE_GRAYSCALE);
	if (!src)
	{
		printf("read data error!\n");
		return -1;
	}
	IplImage* dst = cvCreateImage(cvGetSize(src), 8, 3);
	
	//the parm. for cvFindContours
	CvMemStorage* storage = cvCreateMemStorage(0);
	CvSeq* contour = 0;
	double maxarea = 0;

	//for display
	cvNamedWindow("Source", CV_WINDOW_NORMAL);
	cvShowImage("Source", src);

	//二值化
	cvThreshold(src, src, 120, 255, CV_THRESH_BINARY);
	
	//提取轮廓
	cvFindContours(src, storage, &contour, sizeof(CvContour), CV_RETR_CCOMP, CV_CHAIN_APPROX_SIMPLE);
	cvZero(dst);//清空数组

	/*CvSeq* _contour为了保存轮廓的首指针位置，因为随后contour将用来迭代*/
	CvSeq* _contour = contour;
	

	int maxAreaIdx = -1, iteratorIdx = 0;//n为面积最大轮廓索引，m为迭代索引
	for (int iteratorIdx = 0; contour != 0; contour = contour->h_next, iteratorIdx++/*更新迭代索引*/)
	{

		double tmparea = fabs(cvContourArea(contour));
		if (tmparea > maxarea)
		{
			maxarea = tmparea;
			maxAreaIdx = iteratorIdx;
			continue;
		}
		if (tmparea < minarea)
		{
			//删除面积小于设定值的轮廓
			cvSeqRemove(contour, 0); 
			continue;
		}
		CvRect aRect = cvBoundingRect(contour, 0);
		if ((aRect.width / aRect.height)h_next)
	{
		count++;
		double tmparea = fabs(cvContourArea(contour));
		if (tmparea == maxarea /*k==n*/)
		{
			CvScalar color = CV_RGB(255, 0, 0);
			cvDrawContours(dst, contour, color, color, -1, 1, 8);
		}
		/*k++;*/
	}
	printf("The total number of contours is:%d", count);
	cvNamedWindow("Components", CV_WINDOW_NORMAL);
	cvShowImage("Components", dst);
	cvSaveImage("dst.jpg", dst);
	//roateProcess(dst);
	cvWaitKey(0);
	//销毁窗口和图像存储
	cvDestroyWindow("Source");
	cvReleaseImage(&src);
	cvDestroyWindow("Components");
	cvReleaseImage(&dst);
	return 0;
}

findContours形式

static int getContoursByCplus(char* Imgname, double minarea, double whRatio)
{
	cv::Mat src, dst, canny_output;
	/// Load source image and convert it to gray
	src = imread(Imgname, 0);

	if (!src.data)
	{
		std::cout << "read data error!" << std::endl;
		return -1;
	}
	blur(src, src, Size(3, 3));

	
	//the pram. for findContours,
	vector > contours;
	vector hierarchy;

	/// Detect edges using canny
	Canny(src, canny_output, 80, 255, 3);
	/// Find contours
	findContours(canny_output, contours, hierarchy, CV_RETR_TREE, CV_CHAIN_APPROX_SIMPLE, Point(0, 0));
	//CV_RETR_CCOMP, CV_CHAIN_APPROX_SIMPLE

	double maxarea = 0;
	int maxAreaIdx = 0;

	for (int i = 0; imaxarea)
		{
			maxarea = tmparea;
			maxAreaIdx = i;
			continue;
		}
		
		if (tmparea < minarea)
		{
			//删除面积小于设定值的轮廓
			contours.erase(contours.begin() + i); 
			std::wcout << "delete a small area" << std::endl;
			continue;
		}
		//计算轮廓的直径宽高
		Rect aRect =boundingRect(contours[i]);
		if ((aRect.width / aRect.height)

之后

over!