Fast html5 canvas on iPhone/mobile safari

I finally found a way to optimize 2d canvas drawing on the iPhone 4. Because of the retina display the canvas seems to be rescaled in a slow way (in software?). So even though the rendering itself is relatively fast, the end result is slow. Setting the Viewport The first step is to set the viewport scale to 0.5 which will result in having one pixel per css pixel. <meta name="viewport" content="wid