Machine Vision
Using OpenCV library in LabVIEW
Philippe_RSA wrote:
2) I then had to make use of a tiny app made by Reyn Vlietstra such that the .mat can be used as a pointer to data (there must be a more direct way in LabView.... anyone?) this is called SCM.LabView.Utils.dll (attached).
There is! According to the official documentation for Emgu CV (Working with images -> Accessing the pixels from Mat) there are three ways to obtain pixels data from Mat object. Sadly methods 1 and 2 don't work in LabVIEW - I can't find mat.ToImage in Invoke Node parameters and can't construct a Matrix object to copy into (still no support for Generic types?). But the last method with pinned memory does work!
//load your 3 channel bgr image here
Mat m1 = ...;
//3 channel bgr image data, if it is single channel, the size should be m1.Width * m1.Height
byte[] data = new byte[m1.Width * m1.Height * 3];
GCHandle handle = GCHandle.Alloc(data, GCHandleType.Pinned);
using (Mat m2 = new Mat(m1.Size, DepthType.Cv8U, 3, handle.AddrOfPinnedObject(), m1.Width * 3))
CvInvoke.BitwiseNot(m1, m2);
handle.Free();
I translated this code into LV. Here's a simple example, which shows how to load a RGB image from the file, apply some bilateral filtering (just for fun) and read back the image from Mat object into common IMAQ image.
The BD is kinda lengthy but you may wrap it into a SubVI if you want. I should note also that bitwise NOT is required here to restore colors back to normal.
Tested this with the recent version of Emgu - libemgucv-windesktop-3.3.0.2824.exe.
I have just realized that I did a little mistake when connecting rows' and columns' wires to Reshape Array and double For Loop (I was working with a square image). To get it working with any width / height you need to connect the wires like this:
Sorry for that. 
the key point now is to convert a 2D int array into a mat, which is the image format in emgucv can be processed in emgucv. I got one idea, that is using the method CvArrToMat in emgucv,see picture
but the input arr is a intptr, which can not be wired with a 2D int array. Anyone can give some advice?
