如何检测UIImageView线条笔划是重叠还是穿过另一个笔划

Question

背景

我有一个应用程序，用户可以在其中绘制图表。用户必须通过在图表上滑动来绘制此图表。图表应根据用户滑动绘制垂直和水平线。我有这个工作

问题

我有一个UIImageView，绘图完成。我的问题是我必须限制用户绘制的任何一行，以便不相互重叠。简单的话我不想要这些行重叠或相互交叉。我已经使用下面的视图触摸事件实现了绘图。

-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
    UITouch *touch = [touches anyObject];
    fromPoint = [touch locationInView:_drawingPad];
/*This is for my segment detection .i need to start from the 
   middle of any given segment irrespective of the user point 
   of touch in that segment.*/

    if (fromPoint.y < firstSegment.y) {
        fromPoint.y = firstSegment.y - 30.5;
    }else if (fromPoint.y < seconSegment.y){
        fromPoint.y = seconSegment.y - 30.5;
    } else if (fromPoint.y < thirdSegment.y){
        fromPoint.y = thirdSegment.y - 30.5;
    }else{
        fromPoint.y = fourthSegment.y - 30.5;
    }

}



-(void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
    UITouch *touch = [touches anyObject];
    toPoint = [touch locationInView:_drawingPad];
    CGPoint currentPoint = [touch locationInView:_drawingPad];

    /*This to restrict lines to only being vertical 
      and horizontal Code courtesy stack overflow*/

    double slope = fabs((toPoint.y - fromPoint.y) / (toPoint.x - fromPoint.x));
    if (fromPoint.y == toPoint.y)
    {
        lineRot = horizontal;//lineRot is an enum
    }
    if (slope > 1){
        lineRot = vertical;
    }
    else if(slope < 1){
        lineRot = horizontal;
    }

    if (toPoint.y < firstSegment.y) {
        toPoint.y = firstSegment.y - 30.5;
    }else if (toPoint.y < seconSegment.y){
        toPoint.y = seconSegment.y - 30.5;
    } else if (toPoint.y < thirdSegment.y){
        toPoint.y = thirdSegment.y - 30.5;
    }else{
        toPoint.y = fourthSegment.y - 30.5;
    }

    if (toPoint.x < x) {//This is to avoid a back trace,x is initialized to zero in viewDidLoad
        return;
    } else {
        x = toPoint.x;
        if (!CGPointEqualToPoint(fromPoint, CGPointZero)) {
            UIGraphicsBeginImageContext(_drawingPad.frame.size);
            [_drawingPad.image drawInRect:CGRectMake(0, 0, _drawingPad.frame.size.width, _drawingPad.frame.size.height)];

            CGContextRef context = UIGraphicsGetCurrentContext();            
            CGContextSetLineCap(UIGraphicsGetCurrentContext(), kCGLineCapRound);
            CGContextSetLineWidth(UIGraphicsGetCurrentContext(), 5.0);
            CGContextBeginPath(context);
            CGContextMoveToPoint(context,fromPoint.x, fromPoint.y);
            CGContextSetRGBStrokeColor(UIGraphicsGetCurrentContext(), 0.0, 0.0, 1.0, 1.0);

            if (lineRot == horizontal) {
                CGContextAddLineToPoint(context, toPoint.x, fromPoint.y);
            } else{
                CGContextAddLineToPoint(context, fromPoint.x, toPoint.y);
            }

            CGContextClosePath(context);
            CGContextStrokePath(context);

            _drawingPad.image = UIGraphicsGetImageFromCurrentImageContext();
            UIGraphicsEndImageContext();

        }
    }
}

我尝试过什么

不幸的是没有。事实是我不知道从哪里开始。我看到了这个Hit detection when drawing lines in iOS但是无法得到正在发生的事情以及如何实现。非常感谢任何帮助