如何应用cvsobel + emgucv

Question

I am having some problems in using the cvsobel function. I have read that the cvsobel increases the image depth from 8 bit to 16bit...

Can somebody help me figure out how i can scale it back to 8 bit ...

My code is

Image<Gray, Byte> grayImage = TestImage.Convert<Gray, Byte>().PyrDown().PyrUp(); ;
Image<Gray, Byte> Dest = new Image<Gray, Byte>(grayImage.Size);
Image<Gray, Byte> SobelHorizontal = new Image<Gray, Byte>(grayImage.Size);
CvInvoke.cvCanny(grayImage, Dest, 10, 60, 3);
CvInvoke.cvSobel(Dest, SobelHorizontal, 1, 0, 3); // introduces exception

where TestImage is a color image I take from the user.

The problem here i think is with the declaration of SobelHorizontal ... How do i give a 16 bit depth here and make the function work..

Answer 1

Well EMGU actually has sobel and canny implementations in C#:

 //grayImage.Canny(Gray thresh, Gray threshelinking)
 grayImage.Canny(new Gray(10), new Gray(60));
 //grayImage.Sobel(int xorder, intyorder, int aptureSize)
 grayImage.Sobel(1, 0, 3);

This Should do as you want without the difficulties you face however as vasile mentioned you can declare the data type of your image however you like

Image<Gray,short> Image<Gray,double>, or Image<Gray,float>.

Cheers,

Chris

Answer 2

You can set it directly too.

Example:

Image<Emgu.CV.Structure.Gray, byte> objImagemTemplate = new Image<Emgu.CV.Structure.Gray, byte>(objBitmapTemplate); // Image A
objImagemTemplate = (objImagemTemplate.Canny(new Gray(10), new Gray(60)).Sobel(1, 0, 1)).Convert<Gray, Byte>();

Answer 3

Define SobelHoriz as

Image<Gray, short>

, or whatewer is named the 16 bit integer in C#. Then use the image.convertTo() function to get it back to gray:

Image<gray, byte> sobelDisplay;
sobelHoriz.convertTo(sobelDisplay);

I do not know how you call it in C#. In c++, the image object has a convertTo() member