MATLAB Central Newsreader - mxCreateDoubleMatrix() function

mxCreateDoubleMatrix() function

Geoffroy — Wed, 30 Sep 2009 16:11:00 -0400

I have created a small interface to transfert data between a C++ program and a Matlab workspace. It is working well but I don't know how to create a 3 dimensional matrix to contain a RGB image. I'am able to create and transfert 2D matrix but not a 3D matrix like Im = zeros ( 10, 10, 10 );

How is it possible to do that?

Thank you

Re: mxCreateDoubleMatrix() function

Titus Edelhofer — Wed, 30 Sep 2009 18:16:35 -0400

"Geoffroy " <grsabourin@gmail.com> schrieb im Newsbeitrag
news:h9vvuk$qip$1@fred.mathworks.com...
>I have created a small interface to transfert data between a C++ program
>and a Matlab workspace. It is working well but I don't know how to create a
>3 dimensional matrix to contain a RGB image. I'am able to create and
>transfert 2D matrix but not a 3D matrix like Im = zeros ( 10, 10, 10 );
>
> How is it possible to do that?
>
> Thank you

Hi,
you will need to use mxCreateNumericArray. The doc gives a three dimensional
example.

Titus

Re: mxCreateDoubleMatrix() function

Geoffroy — Thu, 01 Oct 2009 00:33:05 -0400

Yes I have finally found this function but I don't have any result. If I call the function like that

const mwSize dims[]={3,3};
const mwSize NbDimension = 2;
MatlabArray = mxCreateNumericArray( NbDimension, dims, mxUINT16_CLASS, mxREAL );

I put the variable like that
engPutVariable( m_pEngine, in_VarName.c_str(), MatlabArray ) ;

I obtain a 3x3 matrix in the matlab workspace ( only one dimension)

If I try to increase the dimension the function return 0
const mwSize dims[]={3,3};
const mwSize NbDimension = 4;
MatlabArray = mxCreateNumericArray( NbDimension, dims, mxUINT16_CLASS, mxREAL );

"Titus Edelhofer" <titus.edelhofer@mathworks.de> wrote in message <ha07a3$bg6$1@fred.mathworks.com>...
>
> "Geoffroy " <grsabourin@gmail.com> schrieb im Newsbeitrag
> news:h9vvuk$qip$1@fred.mathworks.com...
> >I have created a small interface to transfert data between a C++ program
> >and a Matlab workspace. It is working well but I don't know how to create a
> >3 dimensional matrix to contain a RGB image. I'am able to create and
> >transfert 2D matrix but not a 3D matrix like Im = zeros ( 10, 10, 10 );
> >
> > How is it possible to do that?
> >
> > Thank you
>
> Hi,
> you will need to use mxCreateNumericArray. The doc gives a three dimensional
> example.
>
> Titus
>

Re: mxCreateDoubleMatrix() function

Geoffroy — Thu, 01 Oct 2009 03:19:01 -0400

Re: mxCreateDoubleMatrix() function

James Tursa — Thu, 01 Oct 2009 05:08:01 -0400

"Geoffroy " <grsabourin@gmail.com> wrote in message <ha1735$j6n$1@fred.mathworks.com>...
> Yes I have finally found this function but I don't have any result. If I call the function like that
>
> const mwSize dims[]={3,3};
> const mwSize NbDimension = 2;
> MatlabArray = mxCreateNumericArray( NbDimension, dims, mxUINT16_CLASS, mxREAL );
>
> I put the variable like that
> engPutVariable( m_pEngine, in_VarName.c_str(), MatlabArray ) ;
>
> I obtain a 3x3 matrix in the matlab workspace ( only one dimension)
>
> If I try to increase the dimension the function return 0
> const mwSize dims[]={3,3};
> const mwSize NbDimension = 4;
> MatlabArray = mxCreateNumericArray( NbDimension, dims, mxUINT16_CLASS, mxREAL );

That's because you are reading beyond the end of valid memory. dims still just has 2 elements the way you have written it, not 4. You need to give dims 4 elements, e.g. dims[] = {3,3,3,3}.

James Tursa

Re: mxCreateDoubleMatrix() function

Ryan Ollos — Thu, 01 Oct 2009 05:08:02 -0400

"Geoffroy " <grsabourin@gmail.com> wrote in message <ha0tc1$nv$1@fred.mathworks.com>...
> Yes I have finally found this function but I don't have any result. If I call the function like that
>
> const mwSize dims[]={3,3};
> const mwSize NbDimension = 2;
> MatlabArray = mxCreateNumericArray( NbDimension, dims, mxUINT16_CLASS, mxREAL );

mwSize ndim = 3
mwSize dims = {10, 10, 10}

That should give you the 10 x 10 x 10 array you referred to in your first example.