c#中WinForm用OpencvSharp实现ROI区域提取的示例
时间：2022-09-11 11:25:54 | 栏目：.NET代码 | 点击：次
已经自学OpencvSharp一段时间了(目前工作用的是C#，就学了Opencvsharp了,vs2015，opencvsharp3)，收获也有一些，现在就将我在学习过程中的收获分享出来吧。
图像处理，很常见的问题，但对于大多数时候而言，我们往往不需要去处理整张图片，而是只需要处理一部分，这就涉及到了ROI(Region of interest)的提取了。我目前提取ROI的方法是采用掩膜Mask的方法。具体的思路就是：在图像操作的时候，定义一张同等大小的空的Mask，也就是全部是0，然后将我们想要的ROI轮廓画在Mask上，并填充内部，就会得到新的Mask，这个新的Mask就只有在ROI区域非0，其余地方元素都是0，再把用Cv2.BoundingRect()将包含ROI区域的轮廓的最小矩形找出来，分别将原图与Mask这两幅图像的这个最小矩形部分提出来 ，最后再调用Cv2.BitwiseAnd()这个方法，通常情况而言，一副图像与自己本身进行与运算,输出的还是本身图像，带上掩膜Mask后，就只会输出图像在Mask非0区域部分(也就是我们所需要的ROI)的图像了，这样就实现了我们的ROI提取了。
接下来，就分享几种常见ROI区域提取吧。
部分代码如下：
主要使用的变量
/// 放在yVars.ImgOptions中
public struct ROIMatt
{
public static string Image;//原图
public static bool IsSelectRegion = false;
public static int step; //ROI区域移动步长
public static int angel; // 旋转一次 angel±=step; 旋转角度
public static yDirections direct = yDirections.NULL;
public static yROIRegionType ROIType = yROIRegionType.Rectangle;
// 矩形ROI
// 矩形四个点坐标 都是相对于图像的坐标 而不是相对于picturebox的坐标
// 矩形四个点相对位置 刚开始确定矩形时就这样 经过旋转后位置变 但相对位置还是这样
// 1 2 // 按顺时针数的点 1-->2-->4-->3-->1-->2-->4-->3-->1
// 3 4
public static OpenCvSharp.Point rectFirstPoint = new OpenCvSharp.Point();
public static OpenCvSharp.Point rectSecondPoint = new OpenCvSharp.Point();
public static OpenCvSharp.Point rectThirdPoint = new OpenCvSharp.Point();
public static OpenCvSharp.Point rectFourthPoint = new OpenCvSharp.Point();
public static double rectWidth = 0;
public static double rectHeight = 0;
// 圆形ROI
public static OpenCvSharp.Point cirCenter = new OpenCvSharp.Point(0.0,0.0); // 圆心
public static int cirRadious = 0; // 半径
// 椭圆ROI
public static OpenCvSharp.Point elpCenter = new OpenCvSharp.Point(0.0,0.0); // 椭圆中心点
public static double elpAngel = 0.0;//椭圆倾斜角度
public static double elpLongAxis = 0.0; // 长轴
public static double elpShortAxis = 0.0; // 短轴
}
我的picturebox的SizeMode是StretchImage的，可能看起来跟想要的结果有点差异，但是实际上是一样的。
首先是最常见的矩形。
对于正矩形而言，我们可以直接定义出图像的ROI区域
public Mat(Mat m, Rect roi);
这样定义的图像就是原图m的指定区域了。但对于倾斜的矩阵，RotatedRect，而言，就得需要使用掩膜了，提取ROI的方法以及结果如下：
public static void ImgMattingRect()
{
Mat pic = new Mat(yVars.ImgOptions.ROIMatt.Image);
Mat mask = Mat.Zeros(pic.Size(), MatType.CV_8UC1);
OpenCvSharp.Point2f[] coutours = new OpenCvSharp.Point2f[4];
coutours[0] = yVars.ImgOptions.ROIMatt.rectFirstPoint;
coutours[1] = yVars.ImgOptions.ROIMatt.rectSecondPoint;
coutours[2] = yVars.ImgOptions.ROIMatt.rectFourthPoint;
coutours[3] = yVars.ImgOptions.ROIMatt.rectThirdPoint;
List<OpenCvSharp.Point> listt = new List<OpenCvSharp.Point>();
for (int i = 0; i < coutours.Count(); i++)
{
listt.Add(new OpenCvSharp.Point(coutours[i].X, coutours[i].Y));
}
List<List<OpenCvSharp.Point>> pp = new List<List<OpenCvSharp.Point>>() { listt };
Cv2.FillPoly(mask, pp, new Scalar(255, 255, 255));
OpenCvSharp.Rect rect = Cv2.BoundingRect(coutours);
Mat src = new Mat(pic, rect);
Mat maskROI = new Mat(mask, rect);
Mat picOut = new Mat();
Cv2.BitwiseAnd(src, src, picOut, maskROI);
Form1.Instance.pbxMattImage.Image = yImgConvert.MatToBitmap(picOut);
yVars.ImgOptions.ROIMatt.rectFirstPoint = new OpenCvSharp.Point(0, 0);
yVars.ImgOptions.ROIMatt.rectSecondPoint = new OpenCvSharp.Point(0, 0);
yVars.ImgOptions.ROIMatt.rectThirdPoint = new OpenCvSharp.Point(0, 0);
yVars.ImgOptions.ROIMatt.rectFourthPoint = new OpenCvSharp.Point(0, 0);
}
缩放平移和旋转就只要改变矩形的四个顶点坐标就行了。方法都一样就不赘述了。
圆形ROI区域,
方法如下：
public static void ImgMattingCircle()
{
Mat mm = new Mat(yVars.ImgOptions.ROIMatt.Image);
Mat mask = Mat.Zeros(mm.Size(), MatType.CV_8UC3);
Cv2.Circle(mask, yVars.ImgOptions.ROIMatt.cirCenter, yVars.ImgOptions.ROIMatt.cirRadious, Scalar.Red, 1, LineTypes.AntiAlias);
Cv2.FloodFill(mask, yVars.ImgOptions.ROIMatt.cirCenter, Scalar.Red);
mask.ConvertTo(mask, MatType.CV_8UC1);
int xx = yVars.ImgOptions.ROIMatt.cirCenter.X - yVars.ImgOptions.ROIMatt.cirRadious;
int yy = yVars.ImgOptions.ROIMatt.cirCenter.Y - yVars.ImgOptions.ROIMatt.cirRadious;
int rr = 2 * yVars.ImgOptions.ROIMatt.cirRadious;
// 圆的外接正方形
Rect rect = new Rect(new OpenCvSharp.Point(xx, yy), new OpenCvSharp.Size(rr, rr));
Mat src = new Mat(mm, rect);
Mat maskRoI = new Mat(mask, rect);
Cv2.CvtColor(maskRoI, maskRoI, ColorConversionCodes.BGR2GRAY);
Mat picOut = new Mat();
Cv2.BitwiseAnd(src, src, picOut, maskRoI);
Form1.Instance.pbxMattImage.Image = yImgConvert.MatToBitmap(picOut);
yVars.ImgOptions.ROIMatt.cirCenter = new OpenCvSharp.Point(0, 0);
yVars.ImgOptions.ROIMatt.cirRadious = 0;
}
效果展示:
圆形ROI的移动时就只有圆心坐标变 半径不变，而缩放时只改变半径，圆心不变，注意移动时别超出图像界限就行。
椭圆ROI
在Opencvsharp中绘制椭圆有两种方式
//
// 摘要:
// Draws simple or thick elliptic arc or fills ellipse sector
//
// 参数:
// img:
// Image.
//
// box:
// The enclosing box of the ellipse drawn
//
// color:
// Ellipse color.
//
// thickness:
// Thickness of the ellipse boundary. [By default this is 1]
//
// lineType:
// Type of the ellipse boundary. [By default this is LineType.Link8]
public static void Ellipse(InputOutputArray img, RotatedRect box, Scalar color, int thickness = 1, LineTypes lineType = LineTypes.Link8);
//
// 摘要:
// Draws simple or thick elliptic arc or fills ellipse sector
//
// 参数:
// img:
// Image.
//
// center:
// Center of the ellipse.
//
// axes:
// Length of the ellipse axes.
//
// angle:
// Rotation angle.
//
// startAngle:
// Starting angle of the elliptic arc.
//
// endAngle:
// Ending angle of the elliptic arc.
//
// color:
// Ellipse color.
//
// thickness:
// Thickness of the ellipse arc. [By default this is 1]
//
// lineType:
// Type of the ellipse boundary. [By default this is LineType.Link8]
//
// shift:
// Number of fractional bits in the center coordinates and axes' values. [By default
// this is 0]
public static void Ellipse(InputOutputArray img, Point center, Size axes, double angle, double startAngle, double endAngle, Scalar color, int thickness = 1, LineTypes lineType = LineTypes.Link8, int shift = 0);
我们采用第一种方式，即可以将椭圆转化成一个RotatedRect，只要在画RotatedRect的时候改成画椭圆即可，就可以回到第一种矩形的ROI提取上面了， 代码如下：
public static void ImgMattingEllipse()
{
Mat mm = new Mat(yVars.ImgOptions.ROIMatt.Image);
Mat mask = Mat.Zeros(mm.Size(), MatType.CV_8UC3);
RotatedRect rorect = new RotatedRect(yVars.ImgOptions.ROIMatt.elpCenter, new Size2f(yVars.ImgOptions.ROIMatt.elpLongAxis, yVars.ImgOptions.ROIMatt.elpShortAxis), (float)yVars.ImgOptions.ROIMatt.elpAngel);
Cv2.Ellipse(mask, rorect, Scalar.Red);
Mat gray = new Mat();
Cv2.CvtColor(mask, gray, ColorConversionCodes.BGR2GRAY);
Cv2.Threshold(gray, gray, 100, 255, ThresholdTypes.Otsu);
OpenCvSharp.Point[][] contours;
HierarchyIndex[] hierarchly;
Cv2.FindContours(gray, out contours, out hierarchly, RetrievalModes.Tree, ContourApproximationModes.ApproxSimple, new OpenCvSharp.Point(0, 0));
Rect rect = Cv2.BoundingRect(contours[0]);
Cv2.FloodFill(mask, yVars.ImgOptions.ROIMatt.elpCenter, Scalar.Red);
mask.ConvertTo(mask, MatType.CV_8UC1);
Mat src = new Mat(mm, rect);
Mat maskRoI = new Mat(mask, rect);
Cv2.CvtColor(maskRoI, maskRoI, ColorConversionCodes.BGR2GRAY);
Mat picOut = new Mat();
Cv2.BitwiseAnd(src, src, picOut, maskRoI);
Form1.Instance.pbxMattImage.Image = yImgConvert.MatToBitmap(picOut);
}
实验结果如下：
平移缩放旋转等操作就可以看成对RotatedRect的操作即可。