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Basic Drawing Elements

The creation of complex graphics often has a simple beginning. In Cocoa, everything you draw is derived from a set of basic elements that you assemble in your drawing code. These elements are fundamental to all drawing operations and are described in the following sections.

In this section:

Geometry Support
Shape Primitives
Images
Gradients
Text

Geometry Support

Cocoa provides its own data structures for manipulating basic geometric information such as points and rectangles. Cocoa defines the data types listed in Table 1-1. The member fields in each of these data structures are floating-point values.

For information on how to manipulate point, rectangle, and size data types, see “Manipulating Geometric Types.”

Shape Primitives

Cocoa provides support for drawing shape primitives with the NSBezierPath class. You can use this class to create the following basic shapes, some of which are shown in Figure 1-2.

• Lines

• Rectangles

• Ovals and circles

• Arcs

• Bezier cubic curves

Bezier path objects store vector-based path information, making them compact and resolution independent. You can create paths with any of the simple shapes or combine the basic shapes together to create more complex paths. To render those shapes, you set the drawing attributes for the path and then stroke or fill it to “paint” the path to your view.

For more information about drawing shapes, see “Paths.”

Images

Support for images is provided by the NSImage class and its associated image representation classes (NSImageRep and subclasses). The NSImage class contains the basic interface for creating and managing image-related data. The image representation classes provide the infrastructure used by NSImage to manipulate the underlying image data.

Images can be loaded from existing files or created on the fly. Figure 1-3 shows some bitmap images loaded from files.

Cocoa supports many different image formats, either directly or indirectly. Some of the formats Cocoa supports directly include the following:

• Bitmap images, including the following image formats:

  • BMP

  • GIF

  • JPEG

  • JPEG 2000

  • PNG

  • TIFF

• Images based on Encapsulated PostScript (EPS) data

• Images based on Portable Document Format (PDF) data

• Images based on PICT data

• Core Image images

Because they support many types of data, you should not think of image objects strictly as bitmaps. Image objects can also store path-based drawing commands found in EPS, PDF, and PICT files. They can render data provided to them by Core Image. They can interpolate image data as needed and render the image at different resolutions as needed.

For detailed information about Cocoa support for images and the ways to use images in your code, see “Images.”

Gradients

In Mac OS X v10.5 and later, you can use the NSGradient class to create gradient fill patterns.

Text

Cocoa provides an advanced text system for drawing everything from simple strings to formatted text flows. Figure 1-4 shows some basic examples of stylized text that you can create.

Because text layout and rendering using the Cocoa text system is a very complicated process, it is already well documented elsewhere and is not covered in great detail in this document. For basic information about drawing text and for links to more advanced text-related documents, see “Text.”

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