“contentScaleFactor”背后的秘密是什么？与CATiledLayer一起使用的UIView？ [英] What is the secret behind "contentScaleFactor" of UIView when used with CATiledLayer?

问题描述

问候，

我正在开发一款受iOS SDK附带的ZoomingPDFViewer示例启发的应用程序。在某些时候，我找到了以下代码：

I'm working on an application inspired by the "ZoomingPDFViewer" example that comes with the iOS SDK. At some point I found the following bit of code:

// to handle the interaction between CATiledLayer and high resolution
// screens, we need to manually set the tiling view's 
// contentScaleFactor to 1.0. (If we omitted this, it would be 2.0 
// on high resolution screens, which would cause the CATiledLayer 
// to ask us for tiles of the wrong scales.)
pageContentView.contentScaleFactor = 1.0;

我试图了解更多关于 contentScaleFactor 和它能做什么。在阅读了提到它的Apple文档的所有内容之后，我搜索了Google并且从未找到确切的答案。

I tried to learn more about contentScaleFactor and what it does. After reading everything of Apple's documentation that mentioned it, I searched Google and never found a definite answer to what it actually does.

以下是一些我很好奇的事情：

Here are a few things I'm curious about:

1. 似乎 contentScaleFactor 对此有一些影响绘制UIView的/ CALayer内容时的图形上下文。这似乎与高分辨率显示器（如Retina显示器）有关。 contentScaleFactor 实际上有什么样的效果呢？

1. It seems that contentScaleFactor has some kind of effect on the graphics context when a UIView's/CALayer's contents are being drawn. This seems to be relevant to high resolution displays (like the Retina Display). What kind of effect does contentScaleFactor really have and on what?

使用<$ c $时c> UIScrollView 并将其设置为缩放，比方说，我的 contentView ; contentView 的所有子视图也正在缩放。这个怎么用？哪些属性 UIScrollView 修改以使视频播放器变得模糊和扩展？

When using a UIScrollView and setting it up to zoom, let's say, my contentView; all subviews of contentView are being scaled, too. How does this work? Which properties does UIScrollView modify to make even video players become blurry and scale up?

TL; DR：UIScrollView的缩放功能如何在引擎盖下工作？我想了解它是如何工作的，所以我可以编写正确的代码。

TL;DR: How does UIScrollView's zooming feature work "under the hood"? I want to understand how it works so I can write proper code.

任何提示和解释都非常感谢！ ：）

Any hints and explanation is highly appreciated! :)

推荐答案

坐标用点表示，而不是像素。 contentScaleFactor 定义点和像素之间的关系：如果它是1，则点和像素是相同的，但如果它是2（如视网膜显示），则表示每个点都有两个像素。

Coordinates are expressed in points not pixels. contentScaleFactor defines the relation between point and pixels: if it is 1, points and pixels are the same, but if it is 2 (like retina displays ) it means that every point has two pixels.

在正常绘图中，使用点意味着您不必担心分辨率：在iphone 3（scaleFactor 1）和iphone4（scaleFactor 2和2倍分辨率），您可以使用相同的坐标和绘图代码。但是，如果您正在绘制图像（直接，作为纹理......）并且仅使用法线坐标（点），则您不能相信像素到点的地图是1到1.如果您这样做，那么每个像素都是如果scaleFactor为2（x方向为2，y为2），图像将对应1点但对应4像素，因此图像可能会变得有点模糊

In normal drawing, working with points means that you don't have to worry about resolutions: in iphone 3 (scaleFactor 1) and iphone4 (scaleFactor 2 and 2x resolution), you can use the same coordinates and drawing code. However, if your are drawing a image (directly, as a texture...) and just using normal coordinates (points), you can't trust that pixel to point map is 1 to 1. If you do, then every pixel of the image will correspond to 1 point but 4 pixels if scaleFactor is 2 (2 in x direction, 2 in y) so images could became a bit blurred

使用 CATiledLayer 你可以使用scalefactor 2获得一些意想不到的结果。我想有 UIView a contentScaleFactor = = 2 并且a contentScale == 2 层混淆了系统，有时会使比例倍增。 Scrollview可能会发生类似的情况。

Working with CATiledLayer you can have some unexpected results with scalefactor 2. I guess that having the UIView a contentScaleFactor==2 and the layer a contentScale==2 confuse the system and sometimes multiplies the scale. Maybe something similar happens with Scrollview.

希望这有点澄清

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