[iOS] 畫個虛線

- (void)makeLineInImageView:(UIImageView *)imageView
{
    UIGraphicsBeginImageContext(imageView.frame.size);
    [imageView.image drawInRect:CGRectMake(0, 0, imageView.frame.size.width, imageView.frame.size.height)];
    CGContextSetLineCap(UIGraphicsGetCurrentContext(), kCGLineCapRound);  //設定線條終點形狀
   
    float lengths[] = {2, 2}; //第一個參數設定每個虛線寬度，第二個參數設定虛線的間隔
    CGContextRef line = UIGraphicsGetCurrentContext();
    CGContextSetStrokeColorWithColor(line, [UIColor grayColor].CGColor);
   
    CGContextSetLineDash(line, 0, lengths, 2);
    CGContextMoveToPoint(line, 0.0f, 0.0f);    //開始畫線
    CGContextAddLineToPoint(line, imageView.frame.size.width, 0.0f);
    CGContextStrokePath(line);
   
    imageView.image = UIGraphicsGetImageFromCurrentImageContext();
}