title: getImageData returns 4 values for 1 pixel
body: <p>I am running the below code and everytime it fires it returns four values.</p>
  
  <pre><code>var imgd = ctx.getImageData(2, 2, 1,1);
  var pix = imgd.data;
  console.log(pix);
  for (var i = 0; n = pix.length, i &lt; n; i += 4) {
      if (pix[i] == 0) {
          alert(i);
      }
  }
  </code></pre>
  
  <p>I am sending in the data for position x = 2 and y = 2. Width and height = 1 pixel each. </p>
  
  <p>I expected the value returned to be a single value. Why does it return 4 values in the console when I click a blaxk part of the image?</p>
  
  <p>It returns 0, 255, 255, 255</p>