使用普通CALayer显示图像或UIImage [英] Display an image or UIImage with a plain CALayer

问题描述

我经常读到使用 CALayer 而不是 UIImageView 是一个性能提升沉重的图像使用。这是有道理的，因为 UIImageView 会导致内存中的3个图像副本，这是Core Animation所需要的。但在我的情况下，我不使用Core Animation。

I've often read that using a CALayer rather than a UIImageView is an performance boost when it comes to heavy image usage. That makes sense, because UIImageView causes 3 copies of the image in memory, which is needed for Core Animation. But in my case I don't use Core Animation.

如何分配 UIImage （或其图像数据）到 CALayer 然后显示它？

How can I assign a UIImage (or its image data) to a CALayer and then display it?

推荐答案

UIImage*    backgroundImage = [UIImage imageNamed:kBackName];
CALayer*    aLayer = [CALayer layer];
CGFloat nativeWidth = CGImageGetWidth(backgroundImage.CGImage);
CGFloat nativeHeight = CGImageGetHeight(backgroundImage.CGImage);
CGRect      startFrame = CGRectMake(0.0, 0.0, nativeWidth, nativeHeight);
aLayer.contents = (id)backgroundImage.CGImage;
aLayer.frame = startFrame;

或在Swift游乐场（您必须在Playground的资源文件中提供您自己的PNG图像。我正在使用FrogAvatar的例子。）

or in a Swift playground (you will have to provide your own PNG image in the Playground's resource file. I'm using the example of "FrogAvatar".)

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