workaround iOS 4.3 bug in slicing variant of canvas's drawImage when scaling

gistfile1.js

function _equalRects(left, right) {
  return left.origin.x === right.origin.x && left.origin.y === right.origin.y && left.size.width === right.size.width && left.size.height === right.size.height;
}
function _drawImage(context, image, sourceFrame, destinationFrame) {
  // WORKAROUND - iOS 4.3 bug with the slicing variant of drawImage when scaling
  if (!_equalRects(sourceFrame, destinationFrame)) {
    context.save();

    // clip
    context.beginPath();
    context.rect(destinationFrame.origin.x, destinationFrame.origin.y, destinationFrame.size.width, destinationFrame.size.height);
    context.clip();
    var scale = destinationFrame.size.width / sourceFrame.size.width;

    // translate
    context.translate(destinationFrame.origin.x - sourceFrame.origin.x*scale, destinationFrame.origin.y - sourceFrame.origin.y*scale);

    // scale
    context.scale(scale, scale);

    // draw
    context.drawImage(image, 0.0, 0.0);

    context.restore();
  } else {
    context.drawImage(image, sourceFrame.origin.x, sourceFrame.origin.y, sourceFrame.size.width, sourceFrame.size.height, destinationFrame.origin.x, destinationFrame.origin.y, destinationFrame.size.width, destinationFrame.size.height);
  }
}