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The painting color can be opaque or have a degree of transparency.PDF documents can be treated as a single graphic element but can themselves be arbitrarily complex.This chapter contains relatively simple examples that illustrate basic drawing operations.
Chapter 12. Drawing Offscreen Quartz 2D Graphics How To Achieve MoreSubsequent chapters build on the concepts in these simple examples to show how to achieve more and more complex results. Quartz Graphics Contexts Quartz always draws into a graphics context. As described in Quartz 2D Overview (page 8), a graphics context is an abstract representation of a drawing destination. A window, a bitmap, and a PDF file are examples of destinations that are represented by a graphics context. A Quartz graphics context is an opaque data structure called a CGContextRef. The Quartz routines that affect the context all take a CGContextRef as a parameter. Quartz has no notion of a current context; you always pass a context directly to Quartz functions. Depending on the task, an application either creates a graphics context or obtains one from a framework (such as when the application draws into a window). Use of this website signifies your agreement to our Terms of Use.
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