title: What is the meaning of this OpenCV Matrix Expression?
body: <p>I need help to understand this code snippet about alpha channel blending better. There are 2 Mat data type and both of them are split to get the alpha channel (<code>[3]</code> is the alpha channel of RGBA). Then there is 1 more Mat variable called <code>multiplier</code> which I don't really understand the purpose and how the operation on this variable works.</p>
  
  <pre><code>split(mat1, mat1_split);
  split(mat2, mat2_split);
  Mat multiplier = (mat1_split[3] &amp; mat2_split[3])/255 + 1;  //Need explanation here
  </code></pre>
  
  <p>If I extend the definition of <code>&amp;</code> between <code>mat1_split[3]</code> and <code>mat2_split[3]</code> on Visual Studio, it will show this definition <code>CV_EXPORTS MatExpr operator &amp; (const Mat&amp; a, const Mat&amp; b);</code> . </p>
  
  <p>This probably looks like a beginner question but I couldn't understand the meaning of <code>multiplier</code> operation above.   </p>