在imageView上画线（转）

前提：CoreGraphics.framework

- (void)viewDidLoad {
    [super viewDidLoad];  

    UIImageView *imageView=[[UIImageView alloc] initWithFrame:self.view.frame];
    [self.view addSubview:imageView];  

    self.view.backgroundColor=[UIColor blueColor];  

    UIGraphicsBeginImageContext(imageView.frame.size);
    [imageView.image drawInRect:CGRectMake(0, 0, imageView.frame.size.width, imageView.frame.size.height)];
    CGContextSetLineCap(UIGraphicsGetCurrentContext(), kCGLineCapRound);
    CGContextSetLineWidth(UIGraphicsGetCurrentContext(), 15.0);  //线宽
    CGContextSetAllowsAntialiasing(UIGraphicsGetCurrentContext(), YES);
    CGContextSetRGBStrokeColor(UIGraphicsGetCurrentContext(), 1.0, 0.0, 0.0, 1.0);  //颜色另有UIColor转为RGB方法见博客
    CGContextBeginPath(UIGraphicsGetCurrentContext());
    CGContextMoveToPoint(UIGraphicsGetCurrentContext(), 100, 100);  //起点坐标
    CGContextAddLineToPoint(UIGraphicsGetCurrentContext(), 200, 100);   //终点坐标
    CGContextStrokePath(UIGraphicsGetCurrentContext());
    imageView.image=UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
}