Graphics and paints for iOS systems

1. iOS offers two high quality graphics rendering methods: A. OpenGL es for rendering B.quartz,core Animation, Uikit for drawing

2. The OpenGL ES Framework is mainly applicable to game or high frame rate application development. A C-language based interface for creating 2D and 3D content.

Graphics system of Uikit

3. All the paints in iOS, regardless of OpenGL ES, Quartz, Uikit, or core Animation, occur in the area of the UIView object.

4. UIView invoke DrawRect to trigger a view update is the following:

A. Removing or removing other views of the occlusion view

B. Set the hidden property to no so that it changes from hidden to display state

C. Will attempt to scroll out of the screen and back to the screen

D. The call shown Setneedsdisplay or Setneedsdisplayinrect

5. Ways to improve the performance of the painting:

A. Make the redraw area the smallest

B. Identify the view area as opaque as possible, opaque set to Yes

C. Delete the alpha channel in an opaque PNG file and remove the alpha channel from the opaque PNG file to avoid merging the layers that contain the image, thus greatly simplifying the image synthesis and improving the painting performance.

D. Reusing an existing view during scrolling

E. Avoid purging the original content during scrolling, and by default, Uikit clears the context buffer for the area before the DrawRect method is invoked to update a region of the view. If the buffer is cleared during scrolling, it can be costly to set the Clearscontextbeforedrawing property to No.