用实例分析opencv查找连通区域最大面积-创新互联

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今天在弄一个查找连通的大面积的问题。

要把图像弄成黑底，白字，这样才可以正确找到。

然后调用下边的方法：

RETR_CCOMP:提取所有轮廓，并将轮廓组织成双层结构(two-level hierarchy),顶层为连通域的外围边界，次层位内层边界

#include 
#include 
 
using namespace cv;
using namespace std;
 
int main( int argc, char** argv )
{
  Mat src = imread( argv[1] );
 
  int largest_area=0;
  int largest_contour_index=0;
  Rect bounding_rect;
 
  Mat thr;
  cvtColor( src, thr, COLOR_BGR2GRAY ); //Convert to gray
  threshold( thr, thr, 125, 255, THRESH_BINARY ); //Threshold the gray
  bitwise_not(thr,thr); //这里先变反转颜色
 
  vector > contours; // Vector for storing contours
 
  findContours( thr, contours, RETR_CCOMP, CHAIN_APPROX_SIMPLE ); // Find the contours in the image
 
  for( size_t i = 0; i< contours.size(); i++ ) // iterate through each contour.
  {
    double area = contourArea( contours[i] ); // Find the area of contour
 
    if( area > largest_area )
    {
      largest_area = area;
      largest_contour_index = i;        //Store the index of largest contour
      bounding_rect = boundingRect( contours[i] ); // Find the bounding rectangle for biggest contour
    }
  }
 
  drawContours( src, contours,largest_contour_index, Scalar( 0, 255, 0 ), 2 ); // Draw the largest contour using previously stored index.
 
  imshow( "result", src );
  waitKey();
  return 0;
}