Odtnhj

I am using EmguCV to do simple image processing. I want to remove small contours from my thresholded image so I used connectedcomponentswithstats. Below is my code where I convert any pixel smaller than the minimum size into black - essentially deleting it. The reason I want to do this is to be able to use it in the latter part since it is not compatible with other types.

public Mat Filtered(Mat in_img, string currentDir)

 Mat gray_res = new Mat();
 Mat labels = new Mat();
 Mat stats = new Mat();
 Mat centroids = new Mat();

 CvInvoke.CvtColor(in_img, gray_res, ColorConversion.Bgr2Gray);

 var nlabels = CvInvoke.ConnectedComponentsWithStats(gray_res, labels, stats, centroids, LineType.EightConnected);

 int min_size = 250;

 int sizes = new int[nlabels];

 for (int s = 1; s < nlabels; s++)
 
 sizes[s] = BitConverter.ToInt32(stats.GetData(s, (int)ConnectedComponentsTypes.Area), 0);
 

 Matrix<double> fltr_img = new Matrix<double>(labels.Rows, labels.Cols);
 fltr_img.SetValue(0);

 for (int i = 1; i < nlabels; i++)
 
 int j = BitConverter.ToInt32(stats.GetData(i, (int)ConnectedComponentsTypes.Left), 0); //left most
 int w = BitConverter.ToInt32(stats.GetData(i, (int)ConnectedComponentsTypes.Width), 0); //run width
 int k = BitConverter.ToInt32(stats.GetData(i, (int)ConnectedComponentsTypes.Top), 0); //top most
 int h = BitConverter.ToInt32(stats.GetData(i, (int)ConnectedComponentsTypes.Height), 0); //run height

 if (sizes[i] < min_size)
 
 for (int a = k; a < k + h; a++)
 
 for (int b = j; b < j + w; b++)
 
 fltr_img.Data[a, b] = 255;
 
 
 
 

 //Covnert 2D Matrix to Image
 CvInvoke.Imwrite(currentDir + "filter.jpg", fltr_img);

 Mat subtrahend = CvInvoke.Imread(currentDir + "filter.jpg");

 Mat fnl_img = new Mat();

 CvInvoke.Subtract(in_img, subtrahend, fnl_img);

 return fnl_img;

What I did, in the end, is a little dirty trick to convert the mask into a compatible type Mat which is the original image. With this code, I am getting my result but I am still bothered by it.

You can convert Matrix type by using its Mat property. I don't know what type you need so I used DepthType.Cv8U in my example.

Mat converted = new Mat();
fltr_img.Mat.ConvertTo(converted, DepthType.Cv8U);
Mat fnl_img = new Mat();
CvInvoke.Subtract(in_img, converted, fnl_img);

Alternatively, you can also use Mat and/or Matrix together with substract method. Both implement IInpurArray interface.

CvInvoke.Subtract(in_img, fltr_img, fnl_img); //Tested with EmguCv 3.4.1