如何在MKMapSnapshot上绘制MKPolyline

Question

在iOS 7中,您可以使用MapKit框架制作地图的静态快照.如果您想向某人发送带有位置信息的电子邮件,则非常有用.我唯一缺少的是:如何在该快照上绘制MKPolyline？

Answer 1

这是如何:

- (UIImage *)drawRoute:(MKPolyline *)polyline onSnapshot:(MKMapSnapshot *)snapShot withColor:(UIColor *)lineColor {

UIGraphicsBeginImageContext(snapShot.image.size);
CGRect rectForImage = CGRectMake(0, 0, snapShot.image.size.width, snapShot.image.size.height);

// Draw map
[snapShot.image drawInRect:rectForImage];

// Get points in the snapshot from the snapshot
int lastPointIndex;
int firstPointIndex = 0;
BOOL isfirstPoint = NO;
NSMutableArray *pointsToDraw = [NSMutableArray array];
for (int i = 0; i < polyline.pointCount; i++){
    MKMapPoint point = polyline.points[i];
    CLLocationCoordinate2D pointCoord = MKCoordinateForMapPoint(point);
    CGPoint pointInSnapshot = [snapShot pointForCoordinate:pointCoord];
    if (CGRectContainsPoint(rectForImage, pointInSnapshot)) {
        [pointsToDraw addObject:[NSValue valueWithCGPoint:pointInSnapshot]];
        lastPointIndex = i;
        if (i == 0)
            firstPointIndex = YES;
        if (!isfirstPoint) {
            isfirstPoint = YES;
            firstPointIndex = i;
        }
    }
}

// Adding the first point on the outside too so we have a nice path
    if (lastPointIndex+1 <= polyline.pointCount {
    MKMapPoint point = polyline.points[lastPointIndex+1];
    CLLocationCoordinate2D pointCoord = MKCoordinateForMapPoint(point);
    CGPoint pointInSnapshot = [snapShot pointForCoordinate:pointCoord];
    [pointsToDraw addObject:[NSValue valueWithCGPoint:pointInSnapshot]];
}
// Adding the point before the first point in the map as well (if needed) to have nice path

if (firstPointIndex != 0) {
    MKMapPoint point = polyline.points[firstPointIndex-1];
    CLLocationCoordinate2D pointCoord = MKCoordinateForMapPoint(point);
    CGPoint pointInSnapshot = [snapShot pointForCoordinate:pointCoord];
    [pointsToDraw insertObject:[NSValue valueWithCGPoint:pointInSnapshot] atIndex:0];
}

// Draw that points
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSetLineWidth(context, 3.0);

for (NSValue *point in pointsToDraw){
    CGPoint pointToDraw = [point CGPointValue];
    if ([pointsToDraw indexOfObject:point] == 0){
        CGContextMoveToPoint(context, pointToDraw.x, pointToDraw.y);
    } else {
        CGContextAddLineToPoint(context, pointToDraw.x, pointToDraw.y);
    }
}
CGContextSetStrokeColorWithColor(context, [lineColor CGColor]);
CGContextStrokePath(context);

UIImage *resultingImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return resultingImage;
}

我知道这可能不是最好的方法,所以如果你有更好或更快的方法:请分享:)