1. Graphics For Mac

Having examined the features of Quartz 2D, this chapter now turns our attention to the way applications use the library to create graphics. To use a library efficiently you need to understand what real-world objects and processes the library models.

This is as true in graphics as it is in any computer discipline. Each graphics library has a different collection of drawing primitives, different ways of handling color, and drawing techniques that are particular to that graphics library. All of these give the library a unique character. They not only establish the capabilities of the library, but they also define its limits. Collectively these abstractions and processes are called the imaging model of the library. The next few sections explore the Quartz 2D imaging model. The goal is to introduce some of the important concepts that you have to understand in order to make effective use of the Quartz 2D API.

I've been working on this mac pr cactus for mac. After you obtain a graphics context, you can use Quartz 2D functions to draw to the context, perform operations (such as translations) on the context, and change graphics state parameters, such as line width and fill color. Creating a Window Graphics Context in Mac OS X. Free the bitmap data if it exists.

Later chapters will get into the details of putting the imaging model to work for you. Drawing Primitives Raster-oriented libraries like QuickDraw create drawings using metaphors such as the 'graphics pen.' QuickDraw uses the graphics pen to trace out lines or ovals on the graphics device. Quartz 2D, in contrast, uses object-like drawing primitives. Quartz 2D applications construct shapes, images, or text first, and then they ask the library to draw them. The objects take their attributes, colors and the like, from the graphics environment in which they are drawn.

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Graphics For Mac

Given the richness of the graphics that Quartz 2D creates, it may surprise you to learn that Quartz 2D really only supports three different drawing primitives, sampled images, line art, and text. The real flexibility of Quartz 2D is the rich set of drawing attributes at your disposal when you draw these primitives, as well as the flexibility you enjoy to use Quartz 2D to position and transform these primitives. Line art includes many of the same drawing primitives found in other graphics libraries. Using Quartz 2D, your applications create objects called paths. In a way, paths are similar to the outlines printed in a child's coloring book.

Those outlines are really just collections of straight and curved line segments that encircle an area of the page. The colored shapes combine to create a finished image. Quartz 2D uses paths in a similar fashion. When drawing line art, the application creates paths and then colors those paths to create an image.

Unlike the outlines in the coloring book, however, the edges of a path are infinitely thin. This is a crucial aspect of paths that makes them a resolution independent drawing primitive. More will be said about paths and crayons later in this chapter. Chapter 6, 'Line ArtBuilding Paths,' and Chapter 7, 'Line ArtDrawing,' explore the topic of drawing with paths in detail. A sampled image is a pixel-based picture. One way to describe the origin of the term is to consider the way a Digital Camera takes photographs. When you take a picture with a digital camera, the camera takes the light entering through the lens and projects it onto a special computer chip called a Charge-Coupled Device (CCD).