Drawing with Quartz and OpenGL

Abstract

Every application we’ve built so far has been constructed from views and controls provided to us as part of the UIKit framework. You can do an awful lot with these stock components, and a great many application interfaces can be constructed using only these stock objects. Some applications, however, can’t be fully realized without looking further. For instance, at times, an application needs to be able to do custom drawing. Fortunately for us, we have not one but two separate libraries we can call on for our drawing needs: Quartz 2D, which is part of the Core Graphics framework, and OpenGL ES, which is a cross-platform graphics library. OpenGL ES is a slimmed down version of another cross-platform graphic library called OpenGL. OpenGL ES is a subset of OpenGL designed specifically for embedded systems such as the iPhone (hence the letters “ES”). In this chapter, we’ll explore both of these powerful graphics environments. We’ll build sample applications in both and try to get a sense of which environment to use when.