How to draw histogram using EmguCV and C#

Question

I need to draw two types of histogram, namely monodimensional and tridimensional. I'm a newbie to EMGU and all of the samples I found on the net are in C++ or C. Are there any samples using C# and Emgucv?

Thanks for helping.

Answer 1

The following code will segment the RED GREEN and BLUE Histogram data and put them in an array of floats for whatever use you want.

float[] BlueHist;
float[] GreenHist;
float[] RedHist;

Image<Bgr, Byte> img = new Image<Bgr, byte>("ImageFileName");

DenseHistogram Histo = new DenseHistogram(255, new RangeF(0, 255));

Image<Gray, Byte> img2Blue = img[0];
Image<Gray, Byte> img2Green = img[1];
Image<Gray, Byte> img2Red = img[2];


Histo.Calculate(new Image<Gray, Byte>[] { img2Blue }, true, null);
//The data is here
//Histo.MatND.ManagedArray
BlueHist = new float[256];
Histo.MatND.ManagedArray.CopyTo(BlueHist, 0);

Histo.Clear();

Histo.Calculate(new Image<Gray, Byte>[] { img2Green }, true, null);
GreenHist = new float[256];
Histo.MatND.ManagedArray.CopyTo(GreenHist, 0);

Histo.Clear();

Histo.Calculate(new Image<Gray, Byte>[] { img2Red }, true, null);
RedHist = new float[256];
Histo.MatND.ManagedArray.CopyTo(RedHist, 0);

and this will do the greyscale histogram:

float[] GrayHist;

Image<Gray, Byte> img_gray = new Image<Gray, byte>("ImageFileName");

Histo.Calculate(new Image<Gray, Byte>[] { img_gray }, true, null);
//The data is here
//Histo.MatND.ManagedArray
GrayHist = new float[256];
Histo.MatND.ManagedArray.CopyTo(GrayHist, 0);

Hope this helps,

Cheers,

Chris

[Edit]

To draw the histogram you will need to use either you own or a designed controls such as Zedgraph (This is supplied with with EMGU) here is a very good article on codeproject that shows it's use.

http://www.codeproject.com/KB/graphics/zedgraph.aspx

Cheers

Chris