How to obtain Alpha from cv::mat (For wxWidgets::wxImage)

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The following code is not the entire block of code , instead it is the important pieces needed to get my question across. In short: I am asking how to receive the Alpha data from CV::Mat so that I may pass it into a parameter requesting an unsigned char* as Alpha.

in a scaling function, I have a cv::mat(Destination) that is built as so:

cvImage = convertWxToMatWithAlpha(image); //(cvImage is a CV::Mat)
wxData = (byte*) malloc(width * height * 4);
dst = cv::Mat(height, width, CV_8UC4, wxData);

I then re-size the image and save the results in dst which is a CV::Mat

cv::resize(cvImage,dst, cv::Size(width,height), 0, 0, CV_INTER_LINEAR);

I now need to create a wxImage with alpha using the dst(Be sure this is created using convertWxToMatWithAlpha, this is a function that is defined below in one of the answers.) mat. (Thanks pklab !)

    CV_Assert(dst.type() == CV_8UC4); //Throw an error if this is false.
   //Create a matrix which we will store the data in RBG format.
    cv::mat RGBMatrix; 
    //Convert the dst(BGRA) to RBG and store it in RBGMatrix.
    cv::cvtColor( dst,RGBMatrix, CV_BGRA2RGB ); 
    //Create an alpha matrix which we will mix into the RBGMatrix.
    cv::Mat alpha = cv::Mat::zeros(dst.size(),CV_8UC1); 
    int from_to[] = {3,0};
    cv::mixChannels(&dst,1,&alpha,1,from_to,1);
    if(dst.channels() == 4) //if we have four channels then build the wximage.
    {
        image->Create(dst.cols,dst.rows,RGBMatrix.data,alpha.data,false);
        return true;
    }

The constructor for wxImage I am using is specified as:

 wxImage(int width, int height, unsigned char *data, unsigned char *alpha, bool static_data=false)

EDIT: The above is the correct way of doing this. This is no longer a question, but now just a "how to". I hope this helps people in the future on the internet find a solution to this problem. Also take note of the answers given below this question.