如何在UIView上使用CATransform3D添加特定类型的透视图？ [英] How do I use CATransform3D on a UIView to add a specific type of perspective?

问题描述

我已经创建iPhone应用程序了一段时间，使用基本的转换（旋转，缩放等），但现在我想做一些更复杂一点。

$ b $数学真的不是我最强的点...但我想知道如何添加透视到UIView（见下图）。我在Photoshop中快速嘲笑了使用倾斜选项的屏幕截图。

我已经看了一下stackoverflow的解决方案，我发现我如何应用透视变换到UIView？，它工作得很好 - 但它不是我真正的后，因为最左边的高度大于最右边。

有没有人知道我怎么做这个CATransform3D但没有这些不同的高度？

解决方案

如果你只是想倾斜，你不需要3D变换。仿射变换就足够了。

   - （void）drawRect：（CGRect）rect {
 CGContextRef ctx = UIGraphicsGetCurrentContext ）; 
 CGAffineTransform transform = CGAffineTransformIdentity; 
 transform.b = -0.1; 
 transform.a = 0.9; 
 CGContextConcatCTM（ctx，transform）; 
 //在上下文上绘图
} 
  

这是一个修改的副本;从具有类似变换的项目粘贴，但是您可能需要调整参数a和b。这将从左向右（ 0.1 / 0.9 ）从9升高到1，同时从左到右至90％（ 0.9 ）。

I've been creating iPhone apps for a while now, using basic transformations (rotations, scale, etc) but now I'd like to do something a little more complex.

Maths really isn't my strongest point... but I was wondering how I might go about adding 'perspective' to a UIView (see the image below). I quickly mocked the screenshot up using skew options in Photoshop.

I have had a look around stackoverflow for solutions to this, I found How do I apply a perspective transform to a UIView? which works excellently - but it's not really what i'm after because the height of the left most edge is larger than the right most edge.

Does anyone know how I might go about doing this CATransform3D but without these differing heights?

解决方案

If you just want to skew, you don't need 3D transform. An affine transform will suffice.

-(void)drawRect:(CGRect)rect {
    CGContextRef ctx = UIGraphicsGetCurrentContext();
    CGAffineTransform transform = CGAffineTransformIdentity;
    transform.b = -0.1;
    transform.a = 0.9;
    CGContextConcatCTM(ctx,transform);
    // do drawing on the context
}

this is a modified copy&paste from a project which has a similar transform, but you may need to tune the parameters a and b. This will give a 1 in 9 rise from left to right (0.1/0.9), while condensing from left to right to 90% (0.9).

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