iOS使用Quartz旋转UIImage [英] iOS rotate UIImage using Quartz

问题描述

我有一个自定义的UIView子类

I have a UIView subclass with custom

- (void)drawRect:(CGRect)rect

我想在位置50,50处绘制UIImage并将其旋转20度。

我尝试了以下代码：

I want to draw an UIImage at position 50,50 and have it rotated by 20 degrees.
I tried the following code:

CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSaveGState(context);
CGContextRotateCTM (context, degreesToRad(20));
[image drawAtPoint:CGPointMake(50, 50)];
CGContextRestoreGState(context);

它可以正确旋转图像，但不是50,50 ...

如何在保持正确坐标的同时旋转UIImage？

It rotates the image correctly, but it is not at 50,50...
How can I rotate an UIImage while maintaining the correct coordinates?

推荐答案

为什么要使用drawRect绘制图像？

Why are You using drawRect to draw Image?

UIImageView已经过优化，以使其尽可能快，因此您可以使用以下方式：

UIImageView is optimized enough to be as fast as possible, so You could use something like this:

UIImage *image = [UIImage imageNamed:@"icon.png"];

UIImageView *imageView = [ [ UIImageView alloc ] initWithFrame:CGRectMake(0.0, 0.0, image.size.width, image.size.height) ];

imageView.image = image;

[self addSubview:imageView];

CGAffineTransform rotate = CGAffineTransformMakeRotation( 1.0 / 20.0 * M_PI );

[imageView setTransform:rotate];

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