CODEWITHSUNDEEP
iphoneobjective-ccgcontext
Jumhyn
Jumhyn

Reputation: 6777

Redundant image drawing with CGContextDrawImage

I have one image that I wish to redraw repeatedly over the screen, however, there is a large number of redraws per second, and drawing the image each time makes the app take a huge performance hit. Is there a way to somehow cache the CGImageRef or something that would make CGContextDrawImage perform faster?

Upvotes: 1

Views: 302

Answers (2)

Samantha John
Samantha John

Reputation: 978

A CGLayerRef should be what you need.

From the Apple docs:

Layers are suited for the following:

High-quality offscreen rendering of drawing that you plan to reuse.

  • For example, you might be building a scene and plan to reuse the same background. Draw the background scene to a layer and then draw the layer whenever you need it. One added benefit is that you don’t need to know color space or device-dependent information to draw to a layer.
  • 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.

https://developer.apple.com/library/mac/#documentation/graphicsimaging/Conceptual/drawingwithquartz2d/dq_layers/dq_layers.html#//apple_ref/doc/uid/TP30001066-CH219-TPXREF101

Upvotes: 1

rob mayoff
rob mayoff

Reputation: 386018

Try using UIImageViews and see if it's fast enough. You are allowed to have many UIImageViews. You should set all of their image properties to the same instance of UIImage.

If it's for a game, you should just use a game engine (Unity, Cocos2D, etc.). They have already spent a lot of time figuring out how to make this stuff fast.

Upvotes: 1

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