通过renderInContext放置一个视图以进行绘制： [英] Position a View for drawing via renderInContext:

问题描述

我想在当前的 CGGraphicsContext 中绘制一个 UIView 。我通过 renderInContext：绘制了 UIView ，但是它的位置不正确（总是在左上角）。

I want to draw a UIView in my current CGGraphicsContext. I draw the UIView via renderInContext:, but it's not positioned correctly (always in the top left corner).

我具有 UIView 的所有值，可用于绘制 UIView 。

I have all values of the UIView available for drawing the UIView.

CGRect frame;
CGRect bound;
CGPoint center;
CGAffineTransform transform;

我目前这样设置图层的位置和旋转：

I currently set the position and rotation of the layer like this:

CGContextTranslateCTM(context, frame.origin.x, frame.origin.y);
CGContextRotateCTM(context, (CGFloat) atan2(transform.b, transform.a));

但是该位置由于轮换而不正确，并且与原始位置不同。

如何恢复原始位置？坐标系统在这两者之间没有改变，只是转换 center.x 和 center.y 的问题值转换为适合 CGContextTranslateCTM 的值。

But the position is, due to the rotation, not correct and differs from the original position.
How can I restore the original position? The coordinate system hasn't changed in between, it's just an issue to translate the center.x and center.y values into something appropriate for CGContextTranslateCTM.

编辑：

保存的值正确，保存了正确的边界，中心和变换不是我的问题的起源，而是我的问题的起源，正在通过 CGContextTranslateCTM将这些值设置为可绘制的 CGLayer 。

The saved values are correct, saving the correct bounds, center and transform is not the origin of my issue, the origin of my issue, is setting theses values to the drawable CGLayer via CGContextTranslateCTM.

推荐答案

图形上下文的几何可以调整为 UIView 具有以下代码段的几何：

The geometry of the graphics context can be adjusted to the UIViews geometry with this snippet:

// Center the context around the view's anchor point
CGContextTranslateCTM(context, [view center].x, [view center].y);
// Apply the view's transform about the anchor point
CGContextConcatCTM(context, [view transform]);
// Offset by the portion of the bounds left of and above the anchor point
CGContextTranslateCTM(context,
                      -[view bounds].size.width * [[view layer] anchorPoint].x,
                      -[view bounds].size.height * [[view layer] anchorPoint].y);

这篇关于通过renderInContext放置一个视图以进行绘制：的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！