使用OpenCV 2.4在c ++中计算凸度缺陷 [英] Calculating convexityDefects using OpenCV 2.4 in c++

问题描述

我使用OpenCV 2.4来计算图像的凸包。

我也在做一些处理，以从图像中移除一些噪音，这与问题并不真正相关。

计算convexHull的代码如下：

  ... 
 cv :: Mat sourceImage ; //假设某项已经在这里请
 cv :: vector< cv :: Vec4i>层次; 
 std :: vector< std :: vector< cv :: Point> >轮廓; 
 
 cv :: findContours（sourceImage，contour，hierarchy，CV_RETR_TREE，CV_CHAIN_APPROX_SIMPLE，cv :: Point（0，0））; 
 
 //为每个轮廓找到凸包对象
向量< cv :: vector< cv :: Point> > hull（contours.size（））; 
 
 for（int i = 0; i  {
 convexHull（contoururs [i]，hull [i]，false）; 
} 
 ... 
  

现在拥有convexhull和轮廓想要计算船体的凸度缺陷，通过查看opencv文档，我认为这将是这样：

  cv :: Vec4i缺陷; 
 convexityDefects（cv :: Mat（contour），hull，defects）; 
  

这样做时出现错误：

  OpenCV错误：在convexityDefects中的断言失败（ptnum> 3），文件./opencv/opencv/modules/imgproc/src/contours.cpp，行1969 
  

使用convexityDefects时，我在做什么错误的任何想法？

Opencv convexityDefects文档

提前感谢。

UPDATE

感谢Innuendo回答，我将主循环代码更新为：

  std :: vector< Vec4i>缺陷; 
 vector< cv :: vector< cv :: Point> > hull（contours.size（））; 
 
 for（int i = 0; i  {
 convexHull（contoururs [i]，hull [i]，false）; 
 convexityDefects（contour [i]，hull [i]，defects [i]）;使用这个，我现在得到的错误是：
 
 
 
 
 b 
 $ b  OpenCV错误：无效（hull.checkVector（1，CV_32S）> 2）在convexityDefects 
  
 
 
解决方案
从openCV wiki：
 
 
找到轮廓的凸性缺陷。
 
 
所以你应该把它包含在你的循环中。
  std :: vector< Vec4i>缺陷; 
 vector< cv :: vector< int> > hull（contours.size（））; 
 
 for（int i = 0; i< contours.size（）; i ++）
 {
 convexHull（contoururs [i]，hull [i]，false）; 
 convexityDefects（contour [i]，hull [i]，defects [i]）; 
} 
  
此外，正如你所说，在wiki中说：
 
 
 船体  - 输出凸包。它是索引的整数向量
或点的向量。在第一种情况下，船体元素是原始数组中的凸包点的基于0的
索引（因为凸包点的集合
是原始点集的子集）。在
第二种情况下，外壳元素是凸包本身。
 
 
 
I'm using OpenCV 2.4 to calculate the convex hull of a image. 

I'm also doing some processing to remove some noise from the image, which is not really relevant to the question.

The code to calculate the convexHull is the following:
...
cv::Mat sourceImage; // assume something is already here please
cv::vector<cv::Vec4i> hierarchy;    
std::vector<std::vector<cv::Point> > contours;

cv::findContours( sourceImage, contours, hierarchy, CV_RETR_TREE, CV_CHAIN_APPROX_SIMPLE,cv::Point(0, 0));

// Find the convex hull object for each contour
vector<cv::vector<cv::Point> >hull( contours.size() );

for (int i = 0; i < contours.size(); i++)
{
    convexHull( contours[i], hull[i], false );
}
...
Having both the convexHull and the contours I now want to calculate the convexityDefects of the hull(s), which by looking at opencv documentation I thought it would be like this:
cv::Vec4i defects;  
convexityDefects(cv::Mat(contours),  hull, defects);
Doing this I get this error:
OpenCV Error: Assertion failed (ptnum > 3) in convexityDefects, file ./opencv/opencv/modules/imgproc/src/contours.cpp, line 1969
Any ideas on what I'm doing wrong when using convexityDefects? 

Opencv convexityDefects documentation

Thanks in advance.

UPDATE

Thanks to Innuendo answer I updated the main loop code to:
std::vector<Vec4i> defects; 
vector<cv::vector<cv::Point> >hull( contours.size() );

for (int i = 0; i < contours.size(); i++)
{  
    convexHull( contours[i], hull[i], false );
    convexityDefects(contours[i], hull[i], defects[i]);
}
Using this, the error that I now get is:
OpenCV Error: Assertion failed (hull.checkVector(1, CV_32S) > 2) in convexityDefects

解决方案
From openCV wiki : 

  
Finds the convexity defects of a contour.
So you should include it in your loop.
std::vector<Vec4i> defects; 
vector<cv::vector<int> >hull( contours.size() );

for (int i = 0; i < contours.size(); i++)
{  
    convexHull( contours[i], hull[i], false );
    convexityDefects(contours[i], hull[i], defects[i]);
}
Also, as you mentioned, in wiki is said:

  
hull – Output convex hull. It is either an integer vector of indices
  or vector of points. In the first case, the hull elements are 0-based
  indices of the convex hull points in the original array (since the set
  of convex hull points is a subset of the original point set). In the
  second case, hull elements are the convex hull points themselves.


                        
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