C++ 在 OpenCV 中绘制多边形？
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Drawing Polygons in OpenCV?
提问by fdh
What am I doing wrong here?
我在这里做错了什么？
vector <vector<Point> > contourElement;
for (int counter = 0; counter < contours -> size (); counter ++)
{
contourElement.push_back (contours -> at (counter));
const Point *elementPoints [1] = {contourElement.at (0)};
int numberOfPoints [] = {contourElement.at (0).size ()};
fillPoly (contourMask, elementPoints, numberOfPoints, 1, Scalar (0, 0, 0), 8);
I keep getting an error on the const Point part. The compiler says
我在 const Point 部分不断收到错误消息。编译器说
error: cannot convert 'std::vector<cv::Point_<int>, std::allocator<cv::Point_<int> > >' to 'const cv::Point*' in initialization
What am I doing wrong? (PS: Obviously ignore the missing bracket at the end of the for loop due to this being only part of my code)
我究竟做错了什么？（PS：显然忽略for循环末尾缺少的括号，因为这只是我代码的一部分）
回答by Oliver Zendel
Just for the record (and because the opencv docu is very sparse here) a more reduced snippet using the c++ API:
只是为了记录（并且因为这里的 opencv 文档非常稀疏）使用 c++ API 的更简化的片段：
std::vector<cv::Point> fillContSingle;
[...]
//add all points of the contour to the vector
fillContSingle.push_back(cv::Point(x_coord,y_coord));
[...]
std::vector<std::vector<cv::Point> > fillContAll;
//fill the single contour
//(one could add multiple other similar contours to the vector)
fillContAll.push_back(fillContSingle);
cv::fillPoly( image, fillContAll, cv::Scalar(128));
回答by karlphillip
Let's analyse the offending line:
让我们分析违规行：
const Point *elementPoints [1] = { contourElement.at(0) };
You declared contourElementas vector <vector<Point> >, which means that contourElement.at(0)returns a vector<Point>and not a const cv::Point*. So that's the first error.
您声明contourElement为vector <vector<Point> >，这意味着contourElement.at(0)返回 avector<Point>而不是 a const cv::Point*。所以这是第一个错误。
In the end, you need to do something like:
最后，您需要执行以下操作：
vector<Point> tmp = contourElement.at(0);
const Point* elementPoints[1] = { &tmp[0] };
int numberOfPoints = (int)tmp.size();
Later, call it as:
后来，称之为：
fillPoly (contourMask, elementPoints, &numberOfPoints, 1, Scalar (0, 0, 0), 8);
回答by nikola-miljkovic
contourElement is vector of vector<Point>and not Point :)
so instead of:
contourElement 是向量vector<Point>而不是 Point :) 所以而不是：
const Point *elementPoints
put
放
const vector<Point> *elementPoints
