一、程序
private void button2_Click(object sender, EventArgs e)
{
Mat src = src_img.Clone();
//转化为灰度图
Cv2.CvtColor(src, src, ColorConversionCodes.BGR2GRAY);
InputArray kernel = Cv2.GetStructuringElement(MorphShapes.Rect, new OpenCvSharp.Size(3, 3));
Cv2.MorphologyEx(src, src, MorphTypes.Close, kernel, new OpenCvSharp.Point(-1, -1), 3); //
Cv2.ImShow("MorphologyEx", src);
/*ksize，高斯内核大小，ksize.width和ksize.height必须是正奇数，两者可以不相同，值越大越模糊
sigmaX，Y轴方向的标准差，值越大越模糊
sigmaY，X轴方向的标准差，值越大越模糊 */
Cv2.GaussianBlur(src, src, new OpenCvSharp.Size(11, 11), 2, 2);
Cv2.ImShow("Gaussian", src);
Mat canny_img = new Mat();
Cv2.Canny(src, canny_img, 18, 3, 3, false);
OpenCvSharp.Point[][] contours;
HierarchyIndex[] hierarchly;
/*
findContours找到轮廓
第一个参数:单通道图像矩阵，可以是灰度图，但更常用的是二值图像，一般是经过Canny、拉普拉斯等
第二个参数: contours
第三个参数: hierarchy
第四个参数:轮廓的检索模式
取值一:CV_RETR_EXTERNAL 只检测最外围轮廓，包含在外围轮廓内的内围轮廓被忽略
取值二: CV_RETR_LIST 所有的轮廓，包括内围、外围轮检测廓，但是检测到的轮廓不建立
取值三: CV_RETR_CCOMP 检测所有的轮廓，但所有轮廓只建立两个等级关系，外围为顶层，
取值四: CV_RETR_TREE检测所有轮廓，所有轮廓建立一个等级树结构。外层轮廓包含内层:内层嵌套；
第五个参数:轮廓的近似方法
保存物体边界上所有连续的轮廓点到contours向量内
取值一: CV_CHAIN_APPROX_NONE
取值二:CV_CHAIN APPROX_SIMPLE 仅保存轮廓的拐点信息，把所有轮廓拐点处的点保存入coni
取值三和四: CV_CHAIN_APPROX TC89 L1，CV CHAIN APPROX TC89 KCOS使用teh-Chinl cha
第六个参数:Point偏移量，所有的轮廓信息相对于原始图像对应点的偏移量，相当于在每一个检测出的
*/
Cv2.FindContours(canny_img, out contours, out hierarchly, RetrievalModes.External,
ContourApproximationModes.ApproxSimple, new OpenCvSharp.Point(0, 0));
if (contours.Length == 0)
{
MessageBox.Show("边缘检测失败");
return;
}
Random rnd = new Random();
Scalar color;
color = new Scalar(0, 255,0 );
for (int i = 0; i < contours.Length; i++)
{
color = new Scalar(rnd.Next(0, 255), rnd.Next(8, 255), rnd.Next(8, 255));
Cv2.DrawContours(src, contours, i, color,2, LineTypes.Link4);
}
Cv2.ImShow("contours", src);
//求出面积最大的轮廓
double max_area = 0.0;
double currentArea = 0.0;
OpenCvSharp.Point[] max_contour = null;
for (int i = 0; i < contours.Length; i++)
{
currentArea = Cv2.ContourArea(contours[i]);
if (currentArea > max_area)
{
max_area = currentArea;
max_contour = contours[i];
}
}
//多边形拟合凸包的四个顶点
OpenCvSharp.Point[] hull = Cv2.ConvexHull(max_contour);
double epsilon = 0.02 * Cv2.ArcLength(max_contour, true);
OpenCvSharp.Point[] approx = Cv2.ApproxPolyDP(hull, epsilon, true);
if (approx.Length != 4)
{
MessageBox.Show("拟合凸包的四个顶点失败");
return;
}
Scalar scalar2 = new Scalar(8, 255,255);
Cv2.Line(src, approx[0], approx[1], scalar2, 1, LineTypes.Link4);
Cv2.Line(src, approx[1], approx[2], scalar2,1, LineTypes.Link4);
Cv2.Line(src, approx[2], approx[3], scalar2,1, LineTypes.Link4);
Cv2.Line(src, approx[3], approx[0], scalar2,1, LineTypes.Link4);
//排序
Array.Sort(approx, (cs1, cs2) =>
{
if (cs1 != null && cs1 != null)
{
if (cs1.Y > cs2.Y)
return 1;
else if (cs1.Y == cs2.Y)
{
if (cs1.X < cs2.X)
return 1;
else return -1;
}
else
return -1;
}
return 0;
});
//算法找出的角点
OpenCvSharp.Point2f[] srcpt = new OpenCvSharp.Point2f[4];
srcpt[0] = approx[0];
srcpt[1] = approx[1];
srcpt[2] = approx[3];
srcpt[3] = approx[2];
//最小外接矩形
RotatedRect rect = Cv2.MinAreaRect(srcpt);
Rect box = rect.BoundingRect();
OpenCvSharp.Point2f[] dstpt = new OpenCvSharp.Point2f[4];
dstpt[0].X = box.X; dstpt[0].Y = box.Y;
dstpt[1].X = box.X + box.Width; dstpt[1].Y = box.Y;
dstpt[2].X = box.X + box.Width; dstpt[2].Y = box.Y + box.Height;
dstpt[3].X = box.X; dstpt[3].Y = box.Y + box.Height;
Mat src2 = src_img.Clone();
Mat final = new Mat();
Mat warpmatrix = Cv2.GetPerspectiveTransform(srcpt,dstpt); //获得变换矩阵
Cv2.WarpPerspective(src2,final,warpmatrix,src.Size());//投射变换，将结果赋给final
Bitmap temp = BitmapConverter.ToBitmap(final);
pictureBox2.Image = temp;
DrawLine(srcpt,dstpt);
}
void DrawLine(OpenCvSharp.Point2f[] srcpt, OpenCvSharp.Point2f[] dstpt)
{
Bitmap bmp = new Bitmap(image);
Graphics g = Graphics.FromImage(bmp);
Pen pen = new Pen(Color.Red, 3);
Pen pen2 = new Pen(Color.Blue, 3);
g.DrawLine(pen, srcpt[0].X,srcpt[0].Y,srcpt[1].X,srcpt[1].Y);
g.DrawLine(pen, srcpt[1].X,srcpt[1].Y, srcpt[2].X,srcpt[2].Y);
g.DrawLine(pen, srcpt[2].X,srcpt[2].Y,srcpt[3].X,srcpt[3].Y);
g.DrawLine(pen, srcpt[3].X,srcpt[3].Y,srcpt[0].X, srcpt[0].Y);
g.DrawLine(pen2, dstpt[0].X, dstpt[0].Y, dstpt[1].X,dstpt[1].Y);
g.DrawLine(pen2,dstpt[1].X, dstpt[1].Y, dstpt[2].X, dstpt[2].Y);
g.DrawLine(pen2,dstpt[2].X,dstpt[2].Y, dstpt[3].X, dstpt[3].Y);
g.DrawLine(pen2, dstpt[3].X, dstpt[3].Y, dstpt[0].X, dstpt[0].Y);
pictureBox1.Image = bmp;
}
}
二、运行结果
结果成镜像了
三、资料
[lw112190]的博客：
https://blog.51cto.com/lw112190/6598260?articleABtest=0
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