iOS7 中 MKMapView 的快照

Question

我正在尝试在 iOS7 应用程序中创建 MKMapView 的快照，就像在以前的 iOS 版本中到处推荐的方式一样：

- (UIImage*) renderMapViewToImage
{
   UIGraphicsBeginImageContextWithOptions(mapView.frame.size, NO, 0.0);
   [mapView.layer renderInContext:UIGraphicsGetCurrentContext()];
   UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
   UIGraphicsEndImageContext(); 
   return image;
}

但是，返回的图像是一个黑色矩形，上面有一个蓝色的当前位置点。 我也尝试过使用 mapView 的不同子层，但结果始终相同。

有谁知道如何在 iOS7 中拍摄 MKMapView 快照？

Answer 1

您可以使用MKMapSnapshotter 并从生成的MKMapSnapshot 中获取image。请参阅 WWDC 2013 会议视频的讨论，Putting Map Kit in Perspective。

例如：

MKMapSnapshotOptions *options = [[MKMapSnapshotOptions alloc] init];
options.region = self.mapView.region;
options.scale = [UIScreen mainScreen].scale;
options.size = self.mapView.frame.size;

MKMapSnapshotter *snapshotter = [[MKMapSnapshotter alloc] initWithOptions:options];
[snapshotter startWithCompletionHandler:^(MKMapSnapshot *snapshot, NSError *error) {
    UIImage *image = snapshot.image;
    NSData *data = UIImagePNGRepresentation(image);
    [data writeToFile:[self snapshotFilename] atomically:YES];
}];

话虽如此，renderInContext 解决方案仍然适用于我。有关于仅在 iOS7 的主队列中执行此操作的说明，但它似乎仍然有效。但是MKMapSnapshotter 似乎是更适合 iOS7 的解决方案。

---

如果您想在快照中包含一些注释，您必须手动绘制它们 (!)。这在Putting Map Kit in Perspective 视频的末尾有一些详细的讨论。我不得不说这是我见过的 Apple 建议的最不优雅的实现之一。无论如何，在 iOS 中，它可能看起来像：

MKMapSnapshotOptions *options = [[MKMapSnapshotOptions alloc] init];
options.region = self.mapView.region;
options.scale = [UIScreen mainScreen].scale;
options.size = self.mapView.frame.size;

MKMapSnapshotter *snapshotter = [[MKMapSnapshotter alloc] initWithOptions:options];
[snapshotter startWithQueue:dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0) completionHandler:^(MKMapSnapshot *snapshot, NSError *error) {

    // get the image associated with the snapshot

    UIImage *image = snapshot.image;

    // Get the size of the final image

    CGRect finalImageRect = CGRectMake(0, 0, image.size.width, image.size.height);

    // Get a standard annotation view pin. Clearly, Apple assumes that we'll only want to draw standard annotation pins!

    MKAnnotationView *pin = [[MKPinAnnotationView alloc] initWithAnnotation:nil reuseIdentifier:@""];
    UIImage *pinImage = pin.image;

    // ok, let's start to create our final image

    UIGraphicsBeginImageContextWithOptions(image.size, YES, image.scale);

    // first, draw the image from the snapshotter

    [image drawAtPoint:CGPointMake(0, 0)];

    // now, let's iterate through the annotations and draw them, too

    for (id<MKAnnotation>annotation in self.mapView.annotations)
    {
        CGPoint point = [snapshot pointForCoordinate:annotation.coordinate];
        if (CGRectContainsPoint(finalImageRect, point)) // this is too conservative, but you get the idea
        {
            CGPoint pinCenterOffset = pin.centerOffset;
            point.x -= pin.bounds.size.width / 2.0;
            point.y -= pin.bounds.size.height / 2.0;
            point.x += pinCenterOffset.x;
            point.y += pinCenterOffset.y;

            [pinImage drawAtPoint:point];
        }
    }

    // grab the final image

    UIImage *finalImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

    // and save it

    NSData *data = UIImagePNGRepresentation(finalImage);
    [data writeToFile:[self snapshotFilename] atomically:YES];
}];

对于 MacOS 实现，请参阅该视频了解更多信息，但技术基本相同（创建图像的机制略有不同）。

Answer 2

对于 iOS 10 及更高版本，您可以使用 UIGraphicsImageRenderer 类将任何视图渲染为图像（以防万一您不想使用 MKMapSnapshotter，因为我使用的是 @987654325 @)。

let render = UIGraphicsImageRenderer(size: self.mapView.bounds.size)
let image = render.image { ctx in
  self.mapView.drawHierarchy(in: self.mapView.bounds, afterScreenUpdates: true)
}

结果：

Answer 3

对于 Swift 3

这是我从这篇文章中修改的 swift 3 版本： Render a Map as an Image using MapKit

以下代码允许您基于点（1 个坐标）和折线（多个坐标）对区域进行快照

func takeSnapShot() {
    let mapSnapshotOptions = MKMapSnapshotOptions()

    // Set the region of the map that is rendered. (by one specified coordinate)
    // let location = CLLocationCoordinate2DMake(24.78423, 121.01836) // Apple HQ
    // let region = MKCoordinateRegionMakeWithDistance(location, 1000, 1000)

    // Set the region of the map that is rendered. (by polyline)
    // var yourCoordinates = [CLLocationCoordinate2D]()  <- initinal this array with your polyline coordinates
    let polyLine = MKPolyline(coordinates: &yourCoordinates, count: yourCoordinates.count)
    let region = MKCoordinateRegionForMapRect(polyLine.boundingMapRect)

    mapSnapshotOptions.region = region

    // Set the scale of the image. We'll just use the scale of the current device, which is 2x scale on Retina screens.
    mapSnapshotOptions.scale = UIScreen.main.scale

    // Set the size of the image output.
    mapSnapshotOptions.size = CGSize(width: IMAGE_VIEW_WIDTH, height: IMAGE_VIEW_HEIGHT)

    // Show buildings and Points of Interest on the snapshot
    mapSnapshotOptions.showsBuildings = true
    mapSnapshotOptions.showsPointsOfInterest = true

    let snapShotter = MKMapSnapshotter(options: mapSnapshotOptions)

    snapShotter.start() { snapshot, error in
        guard let snapshot = snapshot else {
            return
        }
        self.imageView.image = snapshot.image
    }
}