将iOS设备坐标转换为drawRect外部的用户坐标

我在UIView中使用CoreGraphics绘制图形，我希望能够使用触摸输入与图形交互。由于触摸是在设备坐标中接收的，因此我需要将其转换为用户坐标，以便将其与图形关联起来，但这已经成为一个障碍，因为

CGContextConvertPointToUserSpace

在图形绘制上下文之外不起作用

这是我试过的

在drawRect中：

CGContextScaleCTM(ctx,...);     
CGContextTranslateCTM(ctx,...); // transform graph to fit the view nicely
self.ctm = CGContextGetCTM(ctx); // save for later
// draw points using user coordinates

CGAffineTransform scale = CGAffineTransformMakeScale(...);
CGAffineTransform translate = CGAffineTransformMakeTranslation(...);
self.myTransform = CGAffineTransformConcat(translate, scale);
// draw points using user coordinates

在my touch事件处理程序中：

CGPoint touchDevice = [gesture locationInView:self]; // touch point in device coords
CGPoint touchUser = CGPointApplyAffineTransform(touchDevice, self.ctm); // doesn't give me what I want
// CGContextConvertPointToUserSpace(touchDevice) <- what I want, but doesn't work here

CGPoint touch = [gesture locationInView:self]; // touch point in view coords
CGPoint touchUser = CGPointApplyAffineTransform(touchPoint, CGAffineTransformInvert(self.myTransform)); // this does the trick

#import <QuartzCore/QuartzCore.h>

CGPoint touch = [gesture locationInView:self]; // view coords

CGSize layerSize = [self.layer frame].size;
UIGraphicsBeginImageContext(layerSize);
CGContextRef context = UIGraphicsGetCurrentContext();

// as in drawRect:
CGContextScaleCTM(...); 
CGContextTranslateCTM(...);

CGPoint touchUser = CGContextConvertPointToUserSpace(context, touch); // now it gives me what I want

UIGraphicsEndImageContext();

CGPoint touch device=[手势位置查看：self]；//设备坐标中的接触点
CGPoint touchUser=cgpointapplyAffinetTransform（touchDevice，self.ctm）；//没有给我想要的
//CGContextConvertPointToUserSpace（touchDevice）我发现CTM已经包含了从地图视图坐标（原点在左上角）到屏幕坐标（原点在左下角）的转换。所以（0,0）被转换为（0800），其中我的视图高度为800，（0,2）映射到（0798）等等。所以我收集了我们正在讨论的3个坐标系：屏幕坐标，视图/设备坐标，用户坐标。（如果我错了，请纠正我。）

CGContext转换（CTM）从用户坐标一直映射到屏幕坐标。我的解决方案是单独维护自己的转换，该转换将用户坐标映射到视图坐标。然后我可以使用它从视图坐标返回用户坐标

我的解决方案：

在drawRect中：

CGContextScaleCTM(ctx,...);     
CGContextTranslateCTM(ctx,...); // transform graph to fit the view nicely
self.ctm = CGContextGetCTM(ctx); // save for later
// draw points using user coordinates

CGAffineTransform scale = CGAffineTransformMakeScale(...);
CGAffineTransform translate = CGAffineTransformMakeTranslation(...);
self.myTransform = CGAffineTransformConcat(translate, scale);
// draw points using user coordinates

在my touch事件处理程序中：

CGPoint touchDevice = [gesture locationInView:self]; // touch point in device coords
CGPoint touchUser = CGPointApplyAffineTransform(touchDevice, self.ctm); // doesn't give me what I want
// CGContextConvertPointToUserSpace(touchDevice) <- what I want, but doesn't work here

CGPoint touch = [gesture locationInView:self]; // touch point in view coords
CGPoint touchUser = CGPointApplyAffineTransform(touchPoint, CGAffineTransformInvert(self.myTransform)); // this does the trick

#import <QuartzCore/QuartzCore.h>

CGPoint touch = [gesture locationInView:self]; // view coords

CGSize layerSize = [self.layer frame].size;
UIGraphicsBeginImageContext(layerSize);
CGContextRef context = UIGraphicsGetCurrentContext();

// as in drawRect:
CGContextScaleCTM(...); 
CGContextTranslateCTM(...);

CGPoint touchUser = CGContextConvertPointToUserSpace(context, touch); // now it gives me what I want

UIGraphicsEndImageContext();

替代解决方案：

另一种方法是手动设置相同的上下文，但我认为这更像是一种黑客行为

在my touch事件处理程序中：

CGPoint touchDevice = [gesture locationInView:self]; // touch point in device coords
CGPoint touchUser = CGPointApplyAffineTransform(touchDevice, self.ctm); // doesn't give me what I want
// CGContextConvertPointToUserSpace(touchDevice) <- what I want, but doesn't work here

CGPoint touch = [gesture locationInView:self]; // touch point in view coords
CGPoint touchUser = CGPointApplyAffineTransform(touchPoint, CGAffineTransformInvert(self.myTransform)); // this does the trick

#import <QuartzCore/QuartzCore.h>

CGPoint touch = [gesture locationInView:self]; // view coords

CGSize layerSize = [self.layer frame].size;
UIGraphicsBeginImageContext(layerSize);
CGContextRef context = UIGraphicsGetCurrentContext();

// as in drawRect:
CGContextScaleCTM(...); 
CGContextTranslateCTM(...);

CGPoint touchUser = CGContextConvertPointToUserSpace(context, touch); // now it gives me what I want

UIGraphicsEndImageContext();

#导入
CGPoint touch=[手势位置视图：self]；//视图坐标
CGSize layerSize=[self.layer frame].size；
UIGraphicsBeginImageContext（layerSize）；
CGContextRef context=UIGraphicsGetCurrentContext（）；
//如drawRect所示：
CGContextScaleCTM（…）；
CGContextTranslateCm（…）；
CGPoint touchUser=CGContextConvertPointToUserSpace（上下文，触摸）；//现在它给了我想要的
UIGraphicsSendImageContext（）；
不明白。。屏幕坐标不是用户坐标？我很困惑我删除了我的答案（得到了屏幕坐标），因为我显然弄错了——我很感激你的一些见解。我很感谢你的帮助。我也很困惑！请看我的编辑。@Daij Djan希望我下面的回答有意义！