Graphics and Drawing | iPhone Apps Tutorial pdf

Graphics and Drawing 

High-quality graphics are an important part of your application’s user interface. Providing high-quality graphics not only makes your application look good, but it also makes your application look like a natural extension to the rest of the system. iPhone OS provides two primary paths for creating high-quality graphics in your system: OpenGL or native rendering using Quartz, Core Animation, and UIKit.
The OpenGL frameworks are geared primarily toward game development or applications that require high frame rates. OpenGL is a C-based interface used to create 2D and 3D content on desktop computers. iPhone OS supports OpenGL drawing through the OpenGL ES framework, which provides support for both the OpenGL ES 2.0 and OpenGL ES v1.1 specifications. OpenGL ES is designed specifically for use on embedded hardware systems and differs in many ways from desktop versions of OpenGL.

For developers who want a more object-oriented drawing approach, iPhone OS provides Quartz, Core Animation, and the graphics support in UIKit. Quartz is the main drawing interface, providing support for path-based drawing, anti-aliased rendering, gradient fill patterns, images, colors, coordinate-space transformations, and PDF document creation, display, and parsing. UIKit provides Objective-C wrappers for Quartz images and color manipulations. Core Animation provides the underlying support for animating changes in many UIKit view properties and can also be used to implement custom animations.
This chapter provides an overview of the drawing process for iPhone applications, along with specific  drawing techniques for each of the supported drawing technologies. This chapter also provides tips and guidance on how to optimize your drawing code for the iPhone OS platform.