iphone石英画两条线在一起会产生蠕虫效应

Question

我用Quartz-2D表示iPhone在地图上显示路线。这条路线是按温度着色的。因为有些街道是黄色的，所以我在路线下用一条稍厚的黑线来创造一个边界效应，这样黄色的部分就可以在黄色的街道上出现。但是，即使黑线和路线一样厚，整个路线看起来就像一条蠕虫(非常丑陋)。我认为这是因为我从一个路线点画到另一个路线点，而不是使用最后一个路线点作为下一个起点。这样，如果有两个路径点丢失，路线将仍然没有削减。

要在没有蠕虫效应的情况下显示两行代码，我需要做什么？

-(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，我得到了一个

<Error>: CGContextClosePath: no current point.

错误，我认为这是胡扯。

请提醒我！)

Answer 1

听起来可能和线头有关。试着用平底帽作图，看看它有帮助。

更新:我知道现在发生了什么。这是简单的“背景”线重叠的像素覆盖在前面的“背景”+“为地面”线绘制。您更改绘制所有“背景”线，然后所有“前台”线避免此问题。你的线条仍然透支一些像素，但只有相同的颜色，所以你不会注意到。(请注意，大多数线头帽样式都超出了直线中的实际点，从而使效果更加明显--更多重叠像素。)

Answer 2

不要画两条线，你能不能画一条，然后用阴影能力

Answer 3

谢谢你们！因此，简单地添加一个阴影或线头没有帮助，效果保持不变。然而，我只是稍微玩了一下代码，结果发现，如果我在完全路径中分别绘制两条线(在两个循环中)，那么效果就消失了！然后，我在背景线上加了正方形的大写，使它稍微好一些。

现在我唯一想知道的是.这是怎么解释的？这是新代码，我稍后会优化它..。

-(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];
   }
}