title: Matrix multiplication in OpenCV
body: <p>I have two Mat images in OpenCV:</p>
  
  <pre><code>Mat ft = Mat::zeros(src.rows,src.cols,CV_32FC1);
  Mat h = Mat::zeros(src.rows,src.cols,CV_32FC1);
  </code></pre>
  
  <p>Both images are the same dimension and are calculated from a single source image.</p>
  
  <p>I would like to multiply these two images but have tried using both</p>
  
  <pre><code>Mat multiply1 = h*ft;
  
  Mat multiply2;
  gemm(h,ft,1,NULL,0,multiply2);
  </code></pre>
  
  <p>but both result in the following assertion failure:</p>
  
  <blockquote>
    <p>OpenCV Error: Assertion failed (a_size.width == len) in unknown function, file ...matmul.cpp
    Termination called after throwing 'cv::exception'</p>
  </blockquote>
  
  <p>What am I doing wrong?</p>