Could OpenCV detect the geometric shapes which is drawn by hand as below? The shape can be a rectangle, triangle, circle, curve, arc,polygon,... I am going to develop an android application which detect these shapes.
Well, I tried it in a harry. Normally you need to skeletonize the input. Anyway. You can reason about the shapes based on their points. Normally a square has 4, a triangle 3, etc. Effort results:
Canny results:
Polygonal approximation:
Console output:
contour points:11
contour points:6
contour points:4
contour points:5
Here is the code:
Mat src=imread("WyoKM.png");
Mat src_gray(src.size(),CV_8UC1);
if (src.empty()) exit(-10);
imshow("img",src);
/// Convert image to gray and blur it
cvtColor( src, src_gray, CV_BGR2GRAY );
threshold(src_gray,src_gray,100,255,src_gray.type());
imshow("img2",src_gray);
Mat canny_output;
vector<vector<Point> > contours;
vector<Vec4i> hierarchy;
/// Detect edges using canny
int thresh=100;
Canny( src_gray, canny_output, thresh, thresh*2, 3 );
imshow("canny",canny_output);
imwrite("canny.jpg",canny_output);
/// Find contours
findContours( canny_output, contours, hierarchy, CV_RETR_TREE, CV_CHAIN_APPROX_SIMPLE, Point(0, 0) );
// testing the approximate polygon
cv::Mat result(src_gray.size(),CV_8U,cv::Scalar(255));
for(int i=0;i<contours.size();i=i+4) //for testing reasons. Skeletonize input.
{
std::vector<cv::Point> poly;
poly.clear();
cv::approxPolyDP(cv::Mat(contours[i]),poly,
5, // accuracy of the approximation
true); // yes it is a closed shape
// Iterate over each segment and draw it
std::vector<cv::Point>::const_iterator itp= poly.begin();
cout<<"\ncontour points:"<<poly.size();
while (itp!=(poly.end()-1)) {
cv::line(result,*itp,*(itp+1),cv::Scalar(0),2);
++itp;
}
// last point linked to first point
cv::line(result,
*(poly.begin()),
*(poly.end()-1),cv::Scalar(20),2);
}
imshow("result",result);
imwrite("results.jpg",result);
cvWaitKey();
来源:https://stackoverflow.com/questions/16682840/opencv-detect-hand-drawing-shapes