Question

我正在使用android openCV，我想检测图像中的三角形，矩形和圆形。所以我这样做：Canny =＆gt; findContours =＆gt; approxPolyDP并获取此图片： Image Hosted by ImageShack.us http://imageshack.us/a/img839/8100/device20130114224716.png

然而，approxPolyDP的结果包含很多顶点，所以我无法确定它是哪个形状。为了消除顶点，我想检测每个轮廓中的线并找到它们的交点。如何为单个轮廓做到这一点？

Answer 1

对于圆圈检测，请使用HoughCircles。

然后在这里你只是寻找简化的多边形（三角形和正方形）。你试过在aptPolyDP中调整epsilon吗？

以下是openCV squares.cpp sample code的示例代码段 - 了解近似精度（epsilon，aboutPolyDP的第三个参数）是如何相对于轮廓的大小设置的。

C ++代码，但openCV接口应该是相同的，所以我确信它可以直接适应您的环境。

 // test each contour
  for( size_t i = 0; i < contours.size(); i++ )
      {
          // approximate contour with accuracy proportional
          // to the contour perimeter
      approxPolyDP(Mat(contours[i]), approx, 
                        arcLength(Mat(contours[i]), true)*0.02, true);

          // square contours should have 4 vertices after approximation
          // relatively large area (to filter out noisy contours)
          // and be convex.
          // Note: absolute value of an area is used because
          // area may be positive or negative - in accordance with the
          // contour orientation
      if( approx.size() == 4 &&
         fabs(contourArea(Mat(approx))) > 1000 &&
         isContourConvex(Mat(approx)) )
          {
          double maxCosine = 0;

          for( int j = 2; j < 5; j++ )
              {
                  // find the maximum cosine of the angle between joint edges
              double cosine = fabs(angle(approx[j%4], approx[j-2], approx[j-1]));
              maxCosine = MAX(maxCosine, cosine);
              }

              // if cosines of all angles are small
              // (all angles are ~90 degree) then write quandrange
              // vertices to resultant sequence

          if( maxCosine < 0.3 )
              squares.push_back(approx);
          }
      }

在轮廓openCV中找到直线

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