iOS 绘制虚线

- (void)drawLineByImageView:(UIImageView *)imageView {

    UIGraphicsBeginImageContext(imageView.frame.size);   //开始画线 划线的frame

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

    //设置线条终点形状

    CGContextSetLineCap(UIGraphicsGetCurrentContext(), kCGLineCapRound);

    CGContextRef line = UIGraphicsGetCurrentContext();

    // 设置颜色

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

    CGFloat lengths[] = {5,2};//先画4个点再画2个点

    CGContextSetLineDash(line,0, lengths,2);//注意2(count)的值等于lengths数组的长度

    CGContextMoveToPoint(line, 0.0, 2.0);    //开始画线

    CGContextAddLineToPoint(line,imageView.frame.size.width,2.0);    CGContextStrokePath(line);

    // UIGraphicsGetImageFromCurrentImageContext()返回的就是image

    UIImage *image =   UIGraphicsGetImageFromCurrentImageContext();

    imageView.image = image;

}