Question

I am studying Core Graphics to make dynamic textures for my project.

A friend told me that i should use CGLayerCreate and CGContextDrawLayerAtPoint
to improve the texture of the brush app that i am building but i haven’t found any book or tutorial that includes CGLayerCreate and CGContextDrawAtPoint.

can you guys tell what’s the use of this two and how will able to code them?

also if you know any core graphics book that includes those please tell me, it’ll surely help me.

thanks!

Answer 1

The Quartz 2D Programming Guide has a chapter that discusses CGLayer objects.

Your friend might be thinking of this use of layers, quoting that chapter:

Repeated drawing. For example, you might want to create a pattern that
consists of the same item drawn over and over. Draw the item to a
layer and then repeatedly draw the layer, as shown in Figure 12-1. Any
Quartz object that you draw repeatedly—including CGPath, CGShading,
and CGPDFPage objects—benefits from improved performance if you draw
it to a CGLayer. Note that a layer is not just for onscreen drawing;
you can use it for graphics contexts that aren’t screen-oriented, such
as a PDF graphics context.

There’s also a very very simple example in the Quartz2DBasics sample app.