用于可缩放 UIScrollView 的矢量绘图

问题描述

我有一个可缩放的 UIScrollView，其中包含一些 CATextLayer 和简单的 CALayer.它们被渲染得很好，但问题是当它们被放大时它们变得模糊.(即使我重画它们)

I have a zoomable UIScrollView with some CATextLayers and simple CALayers in it. They get rendered fine but the problem is when they are zoomed they become blurry. (Even if I redraw them)

当视图放大时，我有哪些选项可以使我的文本不模糊?我应该使用其他东西吗?在 CATextLayer/CALayer 中启用某些东西?欢迎任何想法;)

What would be my options to get my text not blurry when the view is zoomed? Should I use another thing? enable something in CATextLayer/CALayer? Any idea is welcomed ;)

我使用 CALayer 是因为，正如文档中所建议的那样，CALayer 比 UIViews 轻，而且我有数百个.目前它工作顺利.我尝试过使用 UIWebView 并且我的 CALayer 版本更快；)

I am using CALayers because, as suggested in documentation, CALayers are lighter than UIViews and I have hundreds of them. Currently it works smoothly. I have tried with UIWebView and my CALayer version is faster ;)

提前致谢.

推荐答案

iOS 在放大之前对文本进行了光栅化，这就是它如此模糊的原因.您只需修复 CATextLayer 的一项属性 contentsScale，即可在缩放后获得更高质量的渲染.实现这个 UIScrollViewDelegate 方法:

iOS rasterizes the text before the scale-up occurs, that's why it's so blurry. You only need to fix one property of your CATextLayer, contentsScale, to get a higher quality render after zooming. Implement this UIScrollViewDelegate method:

- (void)scrollViewDidEndZooming:(UIScrollView *)scrollView
                       withView:(UIView *)view
                        atScale:(float)scale
{
    [CATransaction begin];
    [CATransaction setValue:[NSNumber numberWithBool:YES] 
                     forKey:kCATransactionDisableActions];
    uglyBlurryTextLayer.contentsScale = scale;
    [CATransaction commit];
}

这告诉图层使用更多像素来渲染文本，并在进行特定更改时禁用核心动画.

This tells the layer to use more pixels to render the text, and it disables Core Animation when making that particular change.

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