问题
在解决问题之前，我们先从问题开始：
你的代码
当您提交代码、寻求帮助时，至少要努力“清理”它。帮助别人帮助你！这里有很多行代码什么也没做。您声明从未使用过的变量。添加一些注释，让人们知道您认为您的代码应该做什么。
Bitmap imgs;
var blurredImage = imgInput.SmoothGaussian(5, 5, 0, 0);
Rectangle rect = CvInvoke.BoundingRectangle(contours[i]);
PointF point = box.Center;
double r = edge1.X + edge1.Y;
// Etc
自适应阈值
以下代码行生成以下图像：
CvInvoke.AdaptiveThreshold(imgout, imgout, 255, Emgu.CV.CvEnum.AdaptiveThresholdType.GaussianC, Emgu.CV.CvEnum.ThresholdType.Binary, 5, 45);
Image 1
Image 2
Image 3
显然这不是您的目标，因为主要轮廓（卡片边缘）完全丢失。作为提示，您始终可以使用以下代码在运行时显示图像以帮助您进行调试。
CvInvoke.NamedWindow("Output");
CvInvoke.Imshow("Output", imgout);
CvInvoke.WaitKey();
解决方案
由于您的示例图像中的卡片主要是与背景相似的值（在 HSV 意义上）。在这种情况下，我认为简单的灰度阈值处理不是正确的方法。我的目的如下：
算法
-
使用 Canny 边缘检测来提取图像中的边缘。
-
扩大边缘，使卡片内容结合在一起。
-
使用轮廓检测来过滤具有最大边界的组合边缘。
-
用旋转的矩形拟合该主轮廓以提取角点。
-
使用角点定义要应用的变换矩阵WarpAffine.
-
扭曲和裁剪图像。
The Code
您可能希望尝试一下 Canny 检测和扩张的参数。
// Working Images
Image<Bgr, byte> imgInput = new Image<Bgr, byte>("Test1.jpg");
Image<Gray, byte> imgEdges = new Image<Gray, byte>(imgInput.Size);
Image<Gray, byte> imgDilatedEdges = new Image<Gray, byte>(imgInput.Size);
Image<Bgr, byte> imgOutput;
// 1. Edge Detection
CvInvoke.Canny(imgInput, imgEdges, 25, 80);
// 2. Dilation
CvInvoke.Dilate(
imgEdges,
imgDilatedEdges,
CvInvoke.GetStructuringElement(
ElementShape.Rectangle,
new Size(3, 3),
new Point(-1, -1)),
new Point(-1, -1),
5,
BorderType.Default,
new MCvScalar(0));
// 3. Contours Detection
VectorOfVectorOfPoint inputContours = new VectorOfVectorOfPoint();
Mat hierarchy = new Mat();
CvInvoke.FindContours(
imgDilatedEdges,
inputContours,
hierarchy,
RetrType.External,
ChainApproxMethod.ChainApproxSimple);
VectorOfPoint primaryContour = (from contour in inputContours.ToList()
orderby contour.GetArea() descending
select contour).FirstOrDefault();
// 4. Corner Point Extraction
RotatedRect bounding = CvInvoke.MinAreaRect(primaryContour);
PointF topLeft = (from point in bounding.GetVertices()
orderby Math.Sqrt(Math.Pow(point.X, 2) + Math.Pow(point.Y, 2))
select point).FirstOrDefault();
PointF topRight = (from point in bounding.GetVertices()
orderby Math.Sqrt(Math.Pow(imgInput.Width - point.X, 2) + Math.Pow(point.Y, 2))
select point).FirstOrDefault();
PointF botLeft = (from point in bounding.GetVertices()
orderby Math.Sqrt(Math.Pow(point.X, 2) + Math.Pow(imgInput.Height - point.Y, 2))
select point).FirstOrDefault();
PointF botRight = (from point in bounding.GetVertices()
orderby Math.Sqrt(Math.Pow(imgInput.Width - point.X, 2) + Math.Pow(imgInput.Height - point.Y, 2))
select point).FirstOrDefault();
double boundingWidth = Math.Sqrt(Math.Pow(topRight.X - topLeft.X, 2) + Math.Pow(topRight.Y - topLeft.Y, 2));
double boundingHeight = Math.Sqrt(Math.Pow(botLeft.X - topLeft.X, 2) + Math.Pow(botLeft.Y - topLeft.Y, 2));
bool isLandscape = boundingWidth > boundingHeight;
// 5. Define warp crieria as triangles
PointF[] srcTriangle = new PointF[3];
PointF[] dstTriangle = new PointF[3];
Rectangle ROI;
if (isLandscape)
{
srcTriangle[0] = botLeft;
srcTriangle[1] = topLeft;
srcTriangle[2] = topRight;
dstTriangle[0] = new PointF(0, (float)boundingHeight);
dstTriangle[1] = new PointF(0, 0);
dstTriangle[2] = new PointF((float)boundingWidth, 0);
ROI = new Rectangle(0, 0, (int)boundingWidth, (int)boundingHeight);
}
else
{
srcTriangle[0] = topLeft;
srcTriangle[1] = topRight;
srcTriangle[2] = botRight;
dstTriangle[0] = new PointF(0, (float)boundingWidth);
dstTriangle[1] = new PointF(0, 0);
dstTriangle[2] = new PointF((float)boundingHeight, 0);
ROI = new Rectangle(0, 0, (int)boundingHeight, (int)boundingWidth);
}
Mat warpMat = new Mat(2, 3, DepthType.Cv32F, 1);
warpMat = CvInvoke.GetAffineTransform(srcTriangle, dstTriangle);
// 6. Apply the warp and crop
CvInvoke.WarpAffine(imgInput, imgInput, warpMat, imgInput.Size);
imgOutput = imgInput.Copy(ROI);
imgOutput.Save("Output1.bmp");
使用两种扩展方法：
static List<VectorOfPoint> ToList(this VectorOfVectorOfPoint vectorOfVectorOfPoint)
{
List<VectorOfPoint> result = new List<VectorOfPoint>();
for (int contour = 0; contour < vectorOfVectorOfPoint.Size; contour++)
{
result.Add(vectorOfVectorOfPoint[contour]);
}
return result;
}
static double GetArea(this VectorOfPoint contour)
{
RotatedRect bounding = CvInvoke.MinAreaRect(contour);
return bounding.Size.Width * bounding.Size.Height;
}
Outputs
元示例
