iphone石英画两条线互相重叠会导致蠕虫效应

Question

我正在使用 iPhone 版 Quartz-2D 在地图上显示路线。路线根据温度着色。因为有些街道是黄色的，所以我在路线线下方使用稍粗的黑线来创建边框效果，以便路线的黄色部分在黄色街道上清晰可见。但是，即使黑线和路线一样粗，整个路线看起来就像一条虫子（非常难看）。我认为这是因为我正在从一个航路点到另一个航路点绘制线条，而不是使用最后一个航路点作为下一个起始航路点。这样，即使缺少几个航路点，路线仍然不会有中断。

我需要做什么才能显示两行而不出现蠕虫效应？

-(void) drawRect:(CGRect) rect
{
CSRouteAnnotation* routeAnnotation = (CSRouteAnnotation*)self.routeView.annotation;

// only draw our lines if we're not int he moddie of a transition and we 
// acutally have some points to draw. 
if(!self.hidden && nil != routeAnnotation.points && routeAnnotation.points.count >   0)
{
    CGContextRef context = UIGraphicsGetCurrentContext(); 

    Waypoint* fromWaypoint = [[Waypoint alloc] initWithDictionary:[routeAnnotation.points objectAtIndex:0]];
    Waypoint* toWaypoint;

    for(int idx = 1; idx < routeAnnotation.points.count; idx++)
    {
        toWaypoint = [[Waypoint alloc] initWithDictionary:[routeAnnotation.points objectAtIndex:idx]];


        CLLocation* fromLocation = [fromWaypoint getLocation];
        CGPoint fromPoint = [self.routeView.mapView convertCoordinate:fromLocation.coordinate toPointToView:self];

        CLLocation* toLocation = [toWaypoint getLocation];
        CGPoint toPoint = [self.routeView.mapView convertCoordinate:toLocation.coordinate toPointToView:self];

        routeAnnotation.lineColor = [fromWaypoint.weather getTemperatureColor];

        CGContextBeginPath(context);
        CGContextSetLineWidth(context, 3.0);
        CGContextSetStrokeColorWithColor(context, [UIColor blackColor].CGColor);
        CGContextMoveToPoint(context, fromPoint.x, fromPoint.y);
        CGContextAddLineToPoint(context, toPoint.x, toPoint.y);
        CGContextStrokePath(context);
        CGContextClosePath(context);

        CGContextBeginPath(context);
        CGContextSetLineWidth(context, 3.0);
        CGContextSetStrokeColorWithColor(context,    routeAnnotation.lineColor.CGColor);
        CGContextMoveToPoint(context, fromPoint.x, fromPoint.y);
        CGContextAddLineToPoint(context, toPoint.x, toPoint.y);
        CGContextStrokePath(context);
        CGContextClosePath(context);


        fromWaypoint = toWaypoint;
    }

    [fromWaypoint release];
    [toWaypoint release];       
}
}

另外，我收到一个

<Error>: CGContextClosePath: no current point.

错误，我认为这是胡说八道。

请提示我！ :)

---

Answer 1

您是否可以只绘制一条线并使用 影子能力？

Answer 2

谢谢你们！因此，简单地添加阴影或线帽并没有帮助，效果保持不变。然而，我只是稍微玩了一下代码，结果发现，如果我分别在完整路径中绘制两条线（在两个 for 循环中），效果就消失了！然后我在背景线上添加了方形线帽，使其看起来更好一些。

现在我唯一想知道的是......对此有何解释？这是新代码，稍后我会优化它......

-(void) drawRect:(CGRect) rect {
CSRouteAnnotation* routeAnnotation = (CSRouteAnnotation*)self.routeView.annotation;

// only draw our lines if we're not int he moddie of a transition and we 
// acutally have some points to draw. 
if(!self.hidden && nil != routeAnnotation.points && routeAnnotation.points.count > 0)
{
    CGContextRef context = UIGraphicsGetCurrentContext(); 


    Waypoint* fromWaypoint = [[Waypoint alloc] initWithDictionary:[routeAnnotation.points objectAtIndex:0]];
    Waypoint* toWaypoint;

    for(int idx = 1; idx < routeAnnotation.points.count; idx++)
    {
        toWaypoint = [[Waypoint alloc] initWithDictionary:[routeAnnotation.points objectAtIndex:idx]];


        CLLocation* fromLocation = [fromWaypoint getLocation];
        CGPoint fromPoint = [self.routeView.mapView convertCoordinate:fromLocation.coordinate toPointToView:self];

        CLLocation* toLocation = [toWaypoint getLocation];
        CGPoint toPoint = [self.routeView.mapView convertCoordinate:toLocation.coordinate toPointToView:self];

        routeAnnotation.lineColor = [fromWaypoint.weather getTemperatureColor];

        CGContextBeginPath(context);
        CGContextSetLineWidth(context, 3.5);
        CGContextSetStrokeColorWithColor(context, [UIColor blackColor].CGColor);
        CGContextSetLineCap(context, kCGLineCapSquare);
        CGContextMoveToPoint(context, fromPoint.x, fromPoint.y);
        CGContextAddLineToPoint(context, toPoint.x, toPoint.y);
        CGContextStrokePath(context);
        CGContextClosePath(context);

        fromWaypoint = toWaypoint;

    }

    // zweite for schleife
    for(int idx = 1; idx < routeAnnotation.points.count; idx++)
    {
        toWaypoint = [[Waypoint alloc] initWithDictionary:[routeAnnotation.points objectAtIndex:idx]];


        CLLocation* fromLocation = [fromWaypoint getLocation];
        CGPoint fromPoint = [self.routeView.mapView convertCoordinate:fromLocation.coordinate toPointToView:self];

        CLLocation* toLocation = [toWaypoint getLocation];
        CGPoint toPoint = [self.routeView.mapView convertCoordinate:toLocation.coordinate toPointToView:self];

        routeAnnotation.lineColor = [fromWaypoint.weather getTemperatureColor];

        CGContextBeginPath(context);

        CGContextSetLineWidth(context, 3.0);
        CGContextSetStrokeColorWithColor(context, routeAnnotation.lineColor.CGColor);
        CGContextSetLineCap(context, kCGLineCapSquare );
        CGContextMoveToPoint(context, fromPoint.x, fromPoint.y);
        CGContextAddLineToPoint(context, toPoint.x, toPoint.y);
        CGContextStrokePath(context);
        CGContextClosePath(context);

    }

    [fromWaypoint release];
   }
}       

Answer 3

听起来这可能与线帽有关。尝试用平端盖绘图，看看是否有帮助。

更新：
我明白现在发生了什么。它只是“背景”线与先前“背景”+“前景”线绘制所覆盖的像素重叠。您更改绘制所有“背景”线然后绘制所有“前景”线可以避免此问题。
您的线条仍然透支了一些像素，但只是颜色相同，因此您不会注意到。
（请注意，大多数线端盖样式都超出了线中的实际点，使效果更加明显 - 更多重叠像素。）

Answer 4

另外，我得到了一个

<错误>：CGContextClosePath：没有当前点。

抚摸路径结束当前路径上下文。