CALayer
Core Animation
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Quartz 2D Coordinate Systems
坐标系是什么?是定义了
defines the range of locations used to express the location and sizes of objects to be drawn on the page
Quartz使用,独立的坐标系--映射到相应的坐标系
从user space---到device space,使用CTM--当前转换矩阵---current transformation matrix
仿射矩阵---平移、旋转、缩放--translation, rotation, and scaling operations
so,告诉我放射变换的目的?
1—what kind of context it is?
2—behavior to match the expectations of the context.
to match the behavior for a context provided by UIKit
行为匹配由UIKit提供的上下文
Some technologies set up their graphics contexts using a different default coordinate system than the one used by Quartz.
PDF graphics context----不提供匹配
只知道有些是不提供匹配的
It is up to your application to adjust any Quartz calls it makes to a context that has a transform applied to it. For example, if you want an image or PDF to draw correctly into a graphics context, your application may need to temporarily adjust the CTM of the graphics context. In iOS, if you use a UIImage object to wrap a CGImage object you create, you do not need to modify the CTM. The UIImage object automatically compensates for the modified coordinate system applied by UIKit.
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