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Posted
27 May 2003

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Hi, I need call some functions of the Intel Library OpenCV from matlab.I'm doing a project with matlab about image processing. My project director told me that there was a direct form for call this Intel library but now it's not possible.then, I'm thinking do it by a MEXfiles and need help!!!
How can I do it?
Thank you very much!!!!
Pedro Fernandez.





There are two ways:
1 Writing your own MEX files.
2 Create an ActiveX control containing the OpenCV codes then using the control inside your mfiles.
Best regards,
A. Riazi





Hi Mr. Riazi,
I want to use your program, I add the lib like that?
#pragma comment(lib, "C:\MATLAB701\extern\lib\win32\lcc\libeng.lib")
#pragma comment(lib, "C:\MATLAB701\extern\lib\win32\lcc\libmx.lib")
#pragma comment(lib, "C:\MATLAB701\extern\lib\win32\lcc\libmatlb.lib")
#pragma comment(lib, "C:\MATLAB701\extern\lib\win32\lcc\libmat.lib")
#pragma comment(lib, "C:\MATLAB701\extern\lib\win32\lcc\libmmfile.lib")
cause my matlab lib are in C:\MATLAB701\extern\lib\win32\lcc.
but I got this error while I compiled the project:
Compiling...
MatlabClass.cpp
c:\testmatlab\eng_demo\matlabclass.cpp(4) : fatal error C1083: Cannot open precompiled header file: 'Debug/MatlabClass.pch': No such file or directory
Error executing cl.exe.
MatlabClass.obj  1 error(s), 0 warning(s)
Your commnets and help is highly appreciated.
Best,
Reza





Salam
The error is because of the precompiled header file (*.pch). Try to clean your build and compile the project again.
Best regards,
A. Riazi





Hi
I read your article about MATLAB.
I, like Steven Romme, would also like to know if this can be used on a simulink model?
I have a simulink model of an aircraft dynamics and would like to extract variables from the simulink model using C++ and feed them into Microsoft Flight Simulator so that the aircraft within the flight sim behaves like a real aircraft.
Passing the data to Microsoft Flight Simulator is the easy part, however getting the variables into my C++ program is what I'm not sure about....
Any advice would be much appreciated.
Thanks, Marc





Hi,
I haven't worked with Simulink yet but I know that there is a solution. I think you can use Realtime workshop toolbox to link Simulink models to your VC++ apps.
Best regards,
A. Riazi





I have succesfully run you demonstration program under Matlab 6.5.0, but have now been upgraded to 7.0.4 (R14 service pack 2), which casues missing header errors. In a previous message, you mentioned that matlab.h needed to be replaced with mclmcr.h for the files to run under Matlab 7. However, neither file exists in my current version. Do you know if the headers been changed yet again, and what is needed now?
Thanks,
James





In fact, neither "matlab.h" nor "matrix.h" is needed to run this demo in Matlab 7.0! Also, "libmatlb.lib" and "libmmfile.lib" should be removed.
Good luck.
Zhang





Hi,
I read your article with great interest and i was wondering if this works with a simulink model as well.
We want to use a control system diagram designed in simulink in a standalone VC++ (MS studio 6 or .NET 2005)
This system has several inputs and outputs and a lot of parameters. What we want to do is create a VC++ program that receives the input from another module over a UDP communication and sends the output back to this module over UDP.
Is it possible to use this simulink model in your suggested way as .m files or .mex files work?
Thank in advance for your reaction!
steven.romme@gmail.com
Steven Romme
 modified at 18:15 Wednesday 22nd March, 2006





Hi,
I sent an email. Sorry that I couldn't reply you soon because I'm in trip. Here is Nowrouz (New days) that are first days of Iranian year.
Best regards,
A. Riazi





Hi,
Thanks firstly for your article and the demos, I found it quite useful!
The problem that I am having currently is to do with calling my own functions in matlab, for example:
I have made a Mfile in matlab called "times_two.m" and inside:
function y = times_two(x)
y = 2*x;
and now I have got your Matlab Engine code working inside my VC++ already, HOWEVER the problems occurs when I tried doing this:
//assume I have all the libraries included
int main(int argc, char* argv[])
{
CMatlabEng matlab;
matlab.Open(NULL);
matlab.EvalString("D = 100;"); // this will work
/* the fellowing will execute BUT does not return the right value */
matlab.EvalString("D = times_two(100);");
mxArray myVal = matlab.GetVariable("D");
// now I use my own print out function
myPrintingFunction(myVal);
matlab.Close();
return 0;
}
Now you would EXPECT the print out of the result will be 200, however it will just print 100 and I have tried many values on it and finally i have track down to the line:
matlab.EvalString("D = times_two(100);");
It seems as if it does not return the value to my variable "D", is it because Matlab Engine do not support userdefined functions or Mfiles? I am pretty sure that the function have been executed, just that it does not return the value...
(I am using Matlab 7 R14  the latest release)
Does anyone have a solution to this??
Thx in advance!!





Did you put your mfile in MATLAB path?
Best regards,
A. Riazi





I had the same problem. However, the matlab console has to be visible otherwise whether the output could be captured nor the result is calculated.





I have compiled and linked engdemo.c in MSVC++ 6.0. It gives 0 errors and 0 warnings. But when executed (please see the code below) only "Hi 1" is getting printed and it just waits. Nothing happens. engOpen(NULL) is not able to connect to MATLAB. Why this is happening.
printf("Hi 1\n");
if (!(ep = engOpen(NULL))) {
fprintf(stderr, "\nCan't start MATLAB engine\n");
return EXIT_FAILURE;
}
printf("Hi 2\n");
Then i tried going to start>Run and typing C:\matlab7\bin\win32\matlab.exe /Automation. It opens MATLAB command window only. After that if i run the engdemo.c it works ans shows the desired result.
Is it not possible to start the MATLAB without doing the /Automation business.
Thanx in advance
Sunil





You used MATLAB 7 but the code that I provided was for MATLAB 6.5. Maybe the interface of MATLAB changed a bit.
The engOpen() runs the MATLAB in background. You can do this manually or in application (by using ShellExecute ).
Best regards,
A. Riazi





Dear Sir,
Thank you for the reply. But it didn't solve my problem. engOpen(NULL) should run the MATLAB in backgroud, but it is not happening to me. I am using MATLAB 7 and Win2K. Please see the code below.
int main()
{
Engine *ep;
if (!(ep = engOpen(NULL)))
{
fprintf(stderr, "\nCan't start MATLAB engine\n");
exit(0);
}
engEvalString(ep, "edit");
engClose(ep);
return 0;
}
This code gives 0 errors and 0 warnings using MSVC++6.0. But when run it doesn't open editor. Why is this so?
It will be gr8 if you can let me know what mistake am i doing, and why the above code is not running.





Your code is correct. As I said maybe the MATLAB interface changed a bit. You know that by using engOpen() you want to use MATLAB COM interface (Automation) to load the MATLAB IDE.
The code that I provide was for MATLAB 6.5 and you want to load MATLAB 7.
Best regards,
A. Riazi





Hello,
I had a BC++ application that invoked the matlab engine using engOpen. It worked perfectly with R13 version of Matlab. With R14, even though I included the new libs, I get the following strange behavior. It still opens the Matlab engine but closes it thereafter. If I use engOpenSingleUse then I get return code of 3. I am not sure what this code means.
Did someone else face this problem with R14 and if yes! how was it resolved.
Thanks,
Pwn





Hi there,
Firstly i would like to say that is a very good article.Congratulations for that.
Now i would come to my problem.I need to call my own function finddepth(w1,w2).m where w1 and w2 are [5][3] matrices , from C.I want to send the matrices w1 and w2 from c to matlab.The function finddepth should process these values and send the result which is an integer back to the C compiler where I would like to print the results.
I have placed the finddepth.m in the work directory of the matlab but i dont have any idea if its running or not as the C rogram doesnt give me any error even if i m putting a wrong name over there.How shall i run my own file?
How to get the result back from the Matlab to the C program and how to print the result?
If possible can you show me a program module with the above application?
I shall be obliged for your help
Stefan





First to find MATLAB runs your mfile or not, you can use OutputBuffer() function to redirect any messages from MATLAB to a user defined buffer.
Second, for getting result of your mfile (in this case a matrix or scalar), use GetVariable() function. This will give you a mxArray pointer. You can use helper functions to print it.
Best regards,
A. Riazi





sir ,
i have some trouble about this, but i already add Matlab headers directory to VStudio directory.when i start to link your demo program, it show up the error message:
"LINK : fatal error LNK1104: cannot open file "libeng.lib"
my develop environment is
Visual C++ 6.0
Matlab 6.5 realese 13
Any help you can give me would be great.
Thanks.





You must also add the library folder to VStudio directory.
Best regards,
A. Riazi






There are library files for MSVC, Borland C++ Builder and WATCOM. You must add the MSVC library file to VStudio.
Best regards,
A. Riazi





How and where do we add the MSVC lib files?







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