assertImageLoaded

var assertImageLoaded = function (img) {
  var complete = img.complete;
  // Workaround for Safari -- it only supports the 
  // complete attrib on script-created images
  if (typeof complete == 'undefined' || complete === false) {
    var test = new Image();
    // If the original image was successfully loaded,
    // src for new one should be pulled from cache
    test.src = img.src;
    complete = test.complete;
  }
  // Check the complete attrib. Use strict equality
  // check -- don't want undefined, null, etc.
  // --------------------------
  // False -- Img failed to load in IE/Safari, or is
  // still trying to load in FF
  if (complete === false) {
    return false;
  }
  // True, but image has no size -- image failed to  // load in FF
  else if (complete === true &&
    img.naturalWidth == 0) {    return false;
  }  // Otherwise all we can do is assume image loaded
  else {    return true;
  }
};