我有以下代码来创建多色 ImageContext：
UIGraphicsBeginImageContext(self.view.frame.size);
[self.imageToDelete drawInRect:CGRectMake(0, 0, self.view.frame.size.width, self.view.frame.size.height)];
CGContextSetLineCap(UIGraphicsGetCurrentContext(), kCGLineCapRound);
CGColorRef mycolor;
mycolor = [[UIColor blueColor] CGColor];
CGPoint mid = CGPointMake(self.frame.size.width/2, self.frame.size.height/2);
CGContextMoveToPoint(UIGraphicsGetCurrentContext(), mid.x, mid.y);
CGContextAddLineToPoint(UIGraphicsGetCurrentContext(), mid.x, mid.y+50);
CGContextSetLineWidth(UIGraphicsGetCurrentContext(),3);
CGContextSetBlendMode(UIGraphicsGetCurrentContext(), kCGBlendModeCopy);
CGContextSetStrokeColorWithColor(UIGraphicsGetCurrentContext(), mycolor);
CGContextStrokePath(UIGraphicsGetCurrentContext());
CGContextFlush(UIGraphicsGetCurrentContext());
mycolor = [[UIColor whiteColor] CGColor];
CGContextMoveToPoint(UIGraphicsGetCurrentContext(), mid.x, mid.y+50);
CGContextAddLineToPoint(UIGraphicsGetCurrentContext(), mid.x, mid.y+75);
CGContextSetLineWidth(UIGraphicsGetCurrentContext(),3);
CGContextSetBlendMode(UIGraphicsGetCurrentContext(), kCGBlendModeCopy);
CGContextSetStrokeColorWithColor(UIGraphicsGetCurrentContext(), mycolor);
CGContextStrokePath(UIGraphicsGetCurrentContext());
CGContextFlush(UIGraphicsGetCurrentContext());
mycolor = [[UIColor cyanColor] CGColor];
CGContextMoveToPoint(UIGraphicsGetCurrentContext(), mid.x, mid.y+75);
CGContextAddLineToPoint(UIGraphicsGetCurrentContext(), mid.x, mid.y+100);
CGContextSetLineWidth(UIGraphicsGetCurrentContext(),3);
CGContextSetBlendMode(UIGraphicsGetCurrentContext(), kCGBlendModeCopy);
CGContextSetStrokeColorWithColor(UIGraphicsGetCurrentContext(), mycolor);
CGContextStrokePath(UIGraphicsGetCurrentContext());
CGContextFlush(UIGraphicsGetCurrentContext());
self.imageToDelete = UIGraphicsGetImageFromCurrentImageContext();
[self.mainImage drawInRect:CGRectMake(0, 0, self.view.frame.size.width, self.view.frame.size.height) blendMode:kCGBlendModeCopy alpha:1.0];
[self.imageToDelete drawInRect:CGRectMake(0, 0, self.view.frame.size.width, self.view.frame.size.height) blendMode:kCGBlendModeNormal alpha:1];
self.mainImage = UIGraphicsGetImageFromCurrentImageContext();
SKSpriteNode *node = [SKSpriteNode spriteNodeWithTexture:[SKTexture textureWithImage:self.mainImage]];
node.zPosition = 100;
node.position = CGPointMake(self.frame.size.width/2, self.frame.size.height/2);
node.size = self.mainImage.size;
[self addChild:node];
UIGraphicsEndImageContext();
这是结果：
我想围绕屏幕中心（或这条线的顶部）旋转这条线，并保持原来的线。有没有办法制作副本，并围绕中心点旋转？澄清一下，midCGPoint 定义为(self.view.frame.size.width/2,self.view.frame.size.height/2)，这是在 Sprite-Kit、iOS、Objective-C 中完成的。