Chapter 4. Drawing and Imaging

The Application Kit has a diverse set of graphics classes. These classes range from NSQuickDrawView, which lets developers use legacy graphics code based on the QuickDraw APIs in their Cocoa application, to NSOpenGLView, which provides a way to display OpenGL-based 3D graphics. The focus of this chapter, however, is on the 2D drawing and imaging classes that provide a high-level interface to Mac OS X’s graphics system, Quartz. Table 4-1 enumerates the classes discussed in this chapter.

Table 4-1. Application Kit drawing and imaging classes

Class	Description
NSAffineTransform	Defines an interface for creating and applying affine transforms that map points in one coordinate space to another
NSBezierPath	Draws PostScript-style lines and curves that enable the construction of arbitrary paths
NSBitmapImageRep	Interprets bitmapped image data, such as those stored as TIFF, BMP, GIF, JPEG, or PNG file types
NSCachedImageRep	Stores image data as a cached representation
NSColor	Represents a color as an object with support for several color spaces and color calibration
NSCustomImageRep	An image representation that allows the client to determine how the image is rendered
NSEPSImageRep	An image representation subclass that represents PostScript (EPS) formatted image data
NSGraphicsContext	Represents configurations for Quartz’s graphics rendering engine and allows the client to determine how characteristics of graphics objects, such as Bezier paths, are rendered
NSImage	Stores and draws an image to screen
NSImageRep	Lets NSImage simultaneously represent an image’s data in several formats defined by its six concrete subclasses
NSPDFImageRep	Represents image data stored as a PDF
NSPICTImageRep	Represents image data in Macintosh PICT format

The Role of Quartz

Quartz is the foundation of Cocoa’s 2D graphics capabilities. It provides many advanced graphics capabilities, including color management, path-based drawing, transparency, and anti-aliasing. It uses the same fundamental model of drawing as Adobe’s Portable Document Format (PDF).

Quartz is actually two individual pieces of software in Mac OS X—Quartz Compositor and Quartz 2D. The Quartz Compositor is the underlying system service responsible for drawing the graphical user interface to screen from sources such as Quartz 2D, QuickTime, OpenGL, and QuickDraw. Quartz 2D, on the other hand, is an Application Programming Interface (API) for drawing and manipulating 2D graphics. This chapter concentrates on Quartz 2D’s drawing functionality.

You can access the Quartz 2D API directly through the CoreGraphics framework, but it is far more convenient to use the Cocoa classes that provide an easy-to-use interface to Quartz, including NSBezierPath, NSView, NSImage, and NSGraphicsContext. These classes provide the functionality to render paths, text, and images to screen or to the printed page.