iOS Programming: The Big Nerd Ranch Guide, Second Edition

For the More Curious: Retina Display

With the release of iPhone 4, Apple introduced the Retina display for the iPhone and iPod touch. The Retina display has much higher resolution – 640x960 pixels compared to 320x480 pixels on earlier devices. Let’s look at what you should do to make graphics look their best on both displays.

For vector graphics, like HypnosisView’s drawRect: method and drawn text, you don’t need to do anything; the same code will render as crisply as the device allows. However, if you draw using Core Graphics functions, these graphics will appear differently on different devices. In Core Graphics, also called Quartz, we describe lines, curves, text, etc. in terms of points. On a non-Retina display, a point is 1x1 pixel. On ...