iphone - 带注释的 map 边界框

Question

我有一种算法，可以为包含一组给定坐标的 map 计算边界框的大小和位置。虽然效果很好，但它产生的边界并不总是容纳我放置在通常位于边界框边缘上的坐标处的图钉:



...并且在大多数情况下，它会产生可接受的结果:

我已经考虑了一段时间，但是我还没有想出一种方法来修改我的算法，以确保图钉始终在边界框内。我的算法在下面列出，任何建议将不胜感激。 :)

MKMapPoint *points = malloc([coordinates count] * sizeof(MKMapPoint));    
MKMapPoint upperRightCorner;
MKMapPoint lowerLeftCorner;

for(int i = 0; i < [coordinates count]; i++) 
{
    CLLocation *location = [coordinates objectAtIndex:i];
    CLLocationCoordinate2D coordinate = CLLocationCoordinate2DMake(herp.coordinate.latitude, herp.coordinate.longitude);

    MKMapPoint point = MKMapPointForCoordinate(coordinate);
    points[i] = point;

    if (i == 0) {
        upperRightCorner = point;
        lowerLeftCorner = point;
    }
    else {
        if (point.x > upperRightCorner.x) upperRightCorner.x = point.x;
        if (point.y > upperRightCorner.y) upperRightCorner.y = point.y;
        if (point.x < lowerLeftCorner.x) lowerLeftCorner.x = point.x;
        if (point.y < lowerLeftCorner.y) lowerLeftCorner.y = point.y;
    }    
}

MKMapRect boundingBox = MKMapRectMake(lowerLeftCorner.x, lowerLeftCorner.y,
                                 upperRightCorner.x - lowerLeftCorner.x,
                                 upperRightCorner.y - lowerLeftCorner.y);

Answer 1

我认为可能已经晚了，但是这是一个对我有用的解决方案，与您的解决方案非常相似，我最终在最后添加了填充。

- (MKCoordinateRegion)boundingBoxForAnnotations:(NSArray *)annotations { 

CLLocationCoordinate2D topLeftCoord; 
topLeftCoord.latitude = -90; 
topLeftCoord.longitude = 180; 

CLLocationCoordinate2D bottomRightCoord; 
bottomRightCoord.latitude = 90; 
bottomRightCoord.longitude = -180; 

for (id<MKAnnotation> annotation in annotations) {

    topLeftCoord.longitude = fmin(topLeftCoord.longitude, annotation.coordinate.longitude); 
    topLeftCoord.latitude = fmax(topLeftCoord.latitude, annotation.coordinate.latitude); 
    bottomRightCoord.longitude = fmax(bottomRightCoord.longitude, annotation.coordinate.longitude); 
    bottomRightCoord.latitude = fmin(bottomRightCoord.latitude, annotation.coordinate.latitude); 
}

MKCoordinateRegion region; 
region.center.latitude = topLeftCoord.latitude - (topLeftCoord.latitude - bottomRightCoord.latitude) * 0.5; 
region.center.longitude = topLeftCoord.longitude + (bottomRightCoord.longitude - topLeftCoord.longitude) * 0.5; 
region.span.latitudeDelta = fabs(topLeftCoord.latitude - bottomRightCoord.latitude) * 1.1; 

region.span.longitudeDelta = fabs(bottomRightCoord.longitude - topLeftCoord.longitude) * 1.1; 

return region;

}