title: Multiplying and adding images with CImg In C++
body: <p>I am trying to find C in the following function in <a href="http://cimg.sourceforge.net" rel="nofollow noreferrer">CImg</a></p>
  
  <p>C=B*L+(1-B)S</p>
  
  <p>Where C, L and S are all RGB images of the same size (and B is a single channel grayscale matte)</p>
  
  <p>I cannot figure out how to loop over the pixels.  I've seen code like:</p>
  
  <pre><code>cimg_forXYZ(S,x,y,z) {... }
  </code></pre>
  
  <p>But I have never see than kind of syntax before, could it be a macro?</p>
  
  <p>Any suggestions are welcome.</p>