iOS Programming: The Big Nerd Ranch Guide

For the More Curious: Retina Display

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

For vector graphics, you do not need to do anything; your 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), lines, curves, text, etc. are described in terms of points. On a non-Retina display, a point is 1x1 pixel. On most Retina displays, a point is 2x2 pixels (Figure 5.15). The exceptions are iPhone ...