cvFindcontours提取的轮廓显示出来是断断续续的点

[ITSophia]

原图（待提取轮廓）

使用cvFindcontours提取的轮廓，可以看到轮廓上的点是断断续续的，想知道这是为什么？
代码如下：

int main()
{
	char * src_filename = "test//0.jpg";
	//读入原图
	IplImage *SrcImage = cvLoadImage(src_filename, CV_LOAD_IMAGE_ANYDEPTH);
	//显示原图
	cvNamedWindow("src", CV_WINDOW_AUTOSIZE);
	cvShowImage("src", SrcImage);

	//二值化
	cvThreshold(SrcImage, SrcImage, 200, 255, THRESH_BINARY_INV);
	CvMemStorage *src_storage = cvCreateMemStorage(0);  //开辟内存空间 
	CvSeq*      src_contour = NULL;
	cvFindContours(SrcImage, src_storage, &src_contour, sizeof(CvContour), CV_RETR_CCOMP, CV_CHAIN_APPROX_NONE);//这函数可选参数还有不少  
	
	
	//显示轮廓
	cvNamedWindow("src_img", CV_WINDOW_AUTOSIZE);
	cvShowImage("src_img", SrcImage);
	cvWaitKey(0);
	cvReleaseImage(&SrcImage);
	cvDestroyWindow("src_img");
	cvDestroyWindow("src");
	return 0;
}

[ITSophia]

使用cvDrawContours()把轮廓绘制出来就可以了。
添加以下代码：

cvZero(SrcImage);
	cvDrawContours(
		SrcImage,
		src_contour,
		cvScalar(100),
		cvScalar(100),
		1                       //#2 需更改区域      
		);

注意，如果图像是没有hole的，如：

这时，如果在cvFindcontours中的参数为CV_RETR_CCOMP，提取的结果是空的，因为对于CV_RETR_CCOMP，它是提取hole和最外框之间的外轮廓和内轮廓，如果是实心图像，即找不到hole，提取不到对应的轮廓，所以此时需要使用参数CV_RETR_LIST，就可以将轮廓提取出来

如果图像为：

用CV_RETR_LIST提取出的轮廓为：

用CV_RETR_CCOMP提取出的轮廓为：

[shiter]

Contour retrieval mode. CV_RETR_EXTERNAL retrieves only the extreme outer contours. It sets hierarchy[i][2]=hierarchy[i][3]=-1 for all the contours. CV_RETR_LIST retrieves all of the contours without establishing any hierarchical relationships. CV_RETR_CCOMP retrieves all of the contours and organizes them into a two-level hierarchy. At the top level, there are external boundaries of the components. At the second level, there are boundaries of the holes. If there is another contour inside a hole of a connected component, it is still put at the top level. CV_RETR_TREE retrieves all of the contours and reconstructs a full hierarchy of nested contours. This full hierarchy is built and shown in the OpenCV contours.c demo. method – Contour approximation method. CV_CHAIN_APPROX_NONE stores absolutely all the contour points. That is, any 2 subsequent points (x1,y1) and (x2,y2) of the contour will be either horizontal, vertical or diagonal neighbors, that is, max(abs(x1-x2),abs(y2-y1))==1. CV_CHAIN_APPROX_SIMPLE compresses horizontal, vertical, and diagonal segments and leaves only their end points. For example, an up-right rectangular contour is encoded with 4 points. CV_CHAIN_APPROX_TC89_L1,CV_CHAIN_APPROX_TC89_KCOS applies one of the flavors of the Teh-Chin chain approximation algorithm. See [TehChin89] for details.

[shiter]

这个主要是参照论文：[Suzuki85] Suzuki, S. and Abe, K., Topological Structural Analysis of Digitized Binary Images by Border Following. CVGIP 30 1, pp 32-46 (1985) 实现的，可以看看论文

[ssbqrm]

是不是显示的问题啊

[ID870177103]

不是这个函数的问题，这个函数不会改变srcimage，是二值化函数的问题，最近也在做opencv，opencv的二值化函数并不理想

[LXHappiness]

我也遇到了同样的问题，然后尝试修改了各项参数，发现改成这样就是连续的轮廓（我用的是java） Imgproc.findContours(cannyContour, contours, new Mat(), Imgproc.RETR_LIST, Imgproc.CHAIN_APPROX_NONE); 关键参数应该是最后一项