iOS 绘图（虚线、椭圆）

#pragma  画虚线

UIImageView *imageView1 = [[UIImageView alloc]initWithFrame:CGRectMake(0, 0, 320, 640)];

imageView1.backgroundColor = [UIColor redColor];

[self.view addSubview:imageView1];

UIGraphicsBeginImageContext(imageView1.frame.size);   //开始画线

CGFloat lengths[] = {10,4};  //划10个点，空4个点

CGContextRef line = UIGraphicsGetCurrentContext(); //设置上下文

CGContextSetStrokeColorWithColor(line, [UIColor blackColor].CGColor);

CGContextSetLineDash(line, 0, lengths, 2);  //画虚线

CGContextMoveToPoint(line, 100.0, 10.0);    //开始画线，设置X,Y的起点位置

CGContextAddLineToPoint(line, 300.0,550.0); //线终点的X,Y位置

CGContextStrokePath(line); //填充

imageView1.image = UIGraphicsGetImageFromCurrentImageContext();

#pragma 画椭圆

UIImageView *imageView1 = [[UIImageView alloc]initWithFrame:CGRectMake(0, 0, 320, 640)];

[self.view addSubview:imageView1];

UIGraphicsBeginImageContext(imageView1.frame.size);   //开始画线

[imageView1.image drawInRect:CGRectMake(0, 0, imageView1.frame.size.width, imageView1.frame.size.height)];

CGContextSetLineCap(UIGraphicsGetCurrentContext(), kCGLineCapRound);  //设置线条终点形状

CGFloat lengths[] = {10,10};

CGContextRef ellipse = UIGraphicsGetCurrentContext();

CGContextSetStrokeColorWithColor(ellipse, [UIColor redColor].CGColor);

CGContextSetLineDash(ellipse, 0, lengths, 2);  //画虚线园

CGRect rectangle = CGRectMake(0,0,200,80);

CGContextAddEllipseInRect(ellipse,rectangle);

CGContextStrokePath(ellipse);

imageView1.image = UIGraphicsGetImageFromCurrentImageContext();