[英]Display an image or UIImage with a plain CALayer
I've often read that using a CALayer
rather than a UIImageView
is an performance boost when it comes to heavy image usage. 我经常读到使用
CALayer
而不是UIImageView
是一个性能提升,当涉及到大量的图像使用。 That makes sense, because UIImageView
causes 3 copies of the image in memory, which is needed for Core Animation. 这是有道理的,因为
UIImageView
在内存中导致3个图像副本,这是Core Animation所需要的。 But in my case I don't use Core Animation. 但在我的情况下,我不使用核心动画。
How can I assign a UIImage
(or its image data) to a CALayer
and then display it? 如何将
UIImage
(或其图像数据)分配给CALayer
然后显示?
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;
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".) 或者在Swift游乐场(你必须在Playground的资源文件中提供你自己的PNG图像。我正在使用“FrogAvatar”的例子。)
//: Playground - noun: a place where people can play
import UIKit
if let backgroundImage = UIImage(named: "FrogAvatar") // you will have to provide your own image in your playground's Resource file
{
let height = backgroundImage.size.height
let width = backgroundImage.size.width
let aLayer = CALayer()
let startFrame = CGRect(x: 0, y: 0, width: width, height: height)
let aView = UIView(frame: startFrame)
aLayer.frame = startFrame
aLayer.contentsScale = aView.contentScaleFactor
aLayer.contents = backgroundImage.cgImage
aView.layer.addSublayer(aLayer)
aView // look at this via the Playground's 👁 eye icon
}
ARC版本需要不同的演员:
self.myView.layer.contents = (__bridge id) self.myImage.CGImage;
CALayer *layer = [[CALayer alloc] init];
layer.contents = (__bridge id _Nullable)([UIImage imageNamed:@"REWIFISocketOff"].CGImage);
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