C#使用OpenCV剪切图像中的圆形和矩形的示例代码

using Emgu.CV;
using Emgu.CV.CvEnum;
using Emgu.CV.Structure;
using System.Drawing;
using System.Windows.Forms;

public void CutRectangleImage(string imagePath)
{
  Image<Bgr, Byte> src = new Image<Bgr, byte>(imagePath);
  int scale = 1;
  if (src.Width > 500)
  {
    scale = 2;
  }
  if (src.Width > 1000)
  {
    scale = 10;
  }
  if (src.Width > 10000)
  {
    scale = 100;
  }
  var size = new Size(src.Width / scale, src.Height / scale);
  Image<Bgr, Byte> srcNewSize = new Image<Bgr, byte>(size);
  CvInvoke.Resize(src, srcNewSize, size);
  //将图像转换为灰度
  UMat grayImage = new UMat();
  CvInvoke.CvtColor(srcNewSize, grayImage, ColorConversion.Bgr2Gray);
  //使用高斯滤波去除噪声
  CvInvoke.GaussianBlur(grayImage, grayImage, new Size(3, 3), 3);
  UMat cannyEdges = new UMat();
  CvInvoke.Canny(grayImage, cannyEdges, 60, 180);//通过边缘化，然后取出轮廓
   
  #region 取三角形和矩形的顶点坐标
  List<Triangle2DF> triangleList = new List<Triangle2DF>();
  List<RotatedRect> boxList = new List<RotatedRect>(); //旋转的矩形框
​
  using (VectorOfVectorOfPoint contours = new VectorOfVectorOfPoint())
  {
    CvInvoke.FindContours(cannyEdges, contours, null, RetrType.List, ChainApproxMethod.ChainApproxSimple);
    int count = contours.Size;
    for (int i = 0; i < count; i++)
    {
      using (VectorOfPoint contour = contours[i])
      using (VectorOfPoint approxContour = new VectorOfPoint())
      {
        CvInvoke.ApproxPolyDP(contour, approxContour, CvInvoke.ArcLength(contour, true) * 0.08, true);
        //仅考虑面积大于50的轮廓
        if (CvInvoke.ContourArea(approxContour, false) > 50)
        {
          if (approxContour.Size == 3) //轮廓有3个顶点：三角形
          {
            System.Drawing.Point[] pts = approxContour.ToArray();
            triangleList.Add(new Triangle2DF(pts[0], pts[1], pts[2]));
          }
          else if (approxContour.Size == 4) //轮廓有4个顶点
          {
            #region 检测角度，如果角度都在 [80, 100] 之间，则为矩形
            bool isRectangle = true;
            System.Drawing.Point[] pts = approxContour.ToArray();
            LineSegment2D[] edges = Emgu.CV.PointCollection.PolyLine(pts, true);
​
            for (int j = 0; j < edges.Length; j++)
            {
              double angle = Math.Abs(edges[(j + 1) % edges.Length].GetExteriorAngleDegree(edges[j]));
              if (angle < 80 || angle > 100)
              {
                isRectangle = false;
                break;
              }
            }
            #endregion
            if (isRectangle) boxList.Add(CvInvoke.MinAreaRect(approxContour));
          }
        }
      }
    }
  }
  #endregion
     
  #region 保存剪切的最大的矩形图片 
  Rectangle rectangle = new Rectangle(0, 0, src.Width, src.Height);
  int maxWidth = 0;
  //boxList = boxList.Where(p => p.Size.Width > 300).ToList();
  for (int i = 0; i < boxList.Count(); i++)
  {
    RotatedRect box = boxList[i];
    Rectangle rectangleTemp = box.MinAreaRect();
    //这里对取到的顶点坐标进行了加宽，因为矩形可能存在角度，这里没有进行角度旋转，所以加宽了取值范围就可以取到完整的图了
    rectangleTemp = new Rectangle(rectangleTemp.X * scale, rectangleTemp.Y * scale, rectangleTemp.Width * scale + scale, rectangleTemp.Height * scale + scale);
    
    //取最大的矩形图片
    if (rectangleTemp.Width > maxWidth)
    {
      maxWidth = rectangleTemp.Width;
      rectangle = rectangleTemp;
    }
  }
  src.Draw(rectangle, new Bgr(System.Drawing.Color.Red), 4);//在图片中画线
  CvInvoke.Imwrite("原始图片.bmp", src); //保存原始图片
  CvInvoke.cvSetImageROI(src.Ptr, rectangle);//设置兴趣点—ROI（region of interest ）
  var clone = src.Clone();
  CvInvoke.Imwrite("剪切的矩形图片.bmp", clone); //保存结果图 
  #endregion
  src.Dispose();
  srcNewSize.Dispose();
  grayImage.Dispose();
}

private void btnRectangle_Click(object sender, RoutedEventArgs e)
{
  System.Windows.Forms.OpenFileDialog frm = new System.Windows.Forms.OpenFileDialog();
  frm.Filter = "(*.jpg,*.png,*.jpeg,*.bmp,*.gif)|*.jgp;*.png;*.jpeg;*.bmp;*.gif|All files(*.*)|*.*";
  if (frm.ShowDialog() == System.Windows.Forms.DialogResult.OK)
  {
    CutRectangleImage(frm.FileName);
  }
}

public void CutCircleImage(string imagePath)
{
  Image<Bgr, Byte> src = new Image<Bgr, byte>(imagePath);
  
  int scale = 1;
  if (src.Width > 500)
  {
    scale = 2;
  }
  if (src.Width > 1000)
  {
    scale = 10;
  }
  if (src.Width > 10000)
  {
    scale = 100;
  }
  var size = new Size(src.Width / scale, src.Height / scale);
  Image<Bgr, Byte> srcNewSize = new Image<Bgr, byte>(size);
  CvInvoke.Resize(src, srcNewSize, size);
  //将图像转换为灰度
  UMat grayImage = new UMat();
  CvInvoke.CvtColor(srcNewSize, grayImage, ColorConversion.Bgr2Gray);
  //使用高斯滤波去除噪声
  CvInvoke.GaussianBlur(grayImage, grayImage, new Size(3, 3), 3);
  //霍夫圆检测
  CircleF[] circles = CvInvoke.HoughCircles(grayImage, HoughModes.Gradient, 2.0, 200.0, 100.0, 180.0, 5);
  
  Rectangle rectangle = new Rectangle();
  float maxRadius = 0;
  foreach (CircleF circle in circles)
  {
    var center = circle.Center;//圆心
    var radius = circle.Radius;//半径
    if (radius > maxRadius)
    {
      maxRadius = radius;
      rectangle = new Rectangle((int)(center.X - radius) * scale,
        (int)(center.Y - radius) * scale,
        (int)radius * 2 * scale + scale,
        (int)radius * 2 * scale + scale);
    }
    srcNewSize.Draw(circle, new Bgr(System.Drawing.Color.Blue), 4);
​
  }
  CvInvoke.Imwrite("原始图片.bmp", srcNewSize); //保存原始图片
  if (maxRadius == 0)
  {
    MessageBox.Show("没有圆形");
  }
  CvInvoke.cvSetImageROI(srcNewSize.Ptr, rectangle);//设置兴趣点—ROI（region of interest ）
  var clone = srcNewSize.Clone();
  CvInvoke.Imwrite("剪切的圆形图片.bmp", clone); //保存结果图 
  src.Dispose();
  srcNewSize.Dispose();
  grayImage.Dispose();
}