使用 CALayer 实现放大镜效果

发布于 2024-09-10 17:18:43 字数 725 浏览 1 评论 0原文

我想实现一个与长按 UITextView 时显示的放大镜完全相同的放大镜。

但是我只使用 CALayers 而不是 UIViews，因此我没有可写入的 drawRect 方法。我想知道我应该在哪里写这个？在 display 方法中？或 drawInContext: 方法？

如何有效地栅格原始视图中的所有图层？（视图被放大）这真的是一个好主意吗：

UIGraphicsBeginImageContext(magnifyView.bounds.size); //magnifyView is the view to be magnified
[magnifyView.layer renderInContext:UIGraphicsGetCurrentContext()]; 
_cache = UIGraphicsGetImageFromCurrentImageContext(); //_cache is an UIImage
UIGraphicsEndImageContext();

然后从这个 UIImage 的 CGImageRef 中获取我需要的部分？

谢谢

原文

I want to implement a magnifier exactly like the one is shown when an UITextView is long pressed.

I got the idea from here: iPhone, reproduce the magnifier effect

But I am working only with CALayers not UIViews, hence I don't have a drawRect method to write in. I wonder where should I write this?
inside display method? or drawInContext: method?

How can I efficiently raster all the layers from the original view? (the view to be magnified) is it really a good idea to do:

UIGraphicsBeginImageContext(magnifyView.bounds.size); //magnifyView is the view to be magnified
[magnifyView.layer renderInContext:UIGraphicsGetCurrentContext()]; 
_cache = UIGraphicsGetImageFromCurrentImageContext(); //_cache is an UIImage
UIGraphicsEndImageContext();

and then get the portion I need from this UIImage's CGImageRef?

Thanks

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