如何在 MKMapSnapshotter 上绘制 CLLocationCoordinate2Ds（在 mapView 打印图像上绘制）

Question

我有带有 CLLocationCoordinate2D 数组的 mapView。我使用这些位置通过MKPolyline 在我的mapView 上画线。现在我想将它存储为 UIimage。我发现有 MKMapSnapshotter 类，但不幸的是我无法在其上绘制叠加层“Snapshotter 对象不会捕获您的应用创建的任何叠加层或注释的视觉表示。”所以我只得到空白地图图像。有什么方法可以用我的叠加层获取图像？

private func generateImageFromMap() {
    let mapSnapshotterOptions = MKMapSnapshotter.Options()
    guard let region = mapRegion() else { return }
    mapSnapshotterOptions.region = region
    mapSnapshotterOptions.size = CGSize(width: 200, height: 200)
    mapSnapshotterOptions.showsBuildings = false
    mapSnapshotterOptions.showsPointsOfInterest = false


    let snapShotter = MKMapSnapshotter(options: mapSnapshotterOptions)
    snapShotter.start() { snapshot, error in
        guard let snapshot = snapshot else {
//do something with image .... 
            let mapImage = snapshot...
        }
    }
}

如何在此图像上添加叠加层？或者也许还有其他方法可以解决这个问题。

Answer 1

不幸的是，您必须自己绘制它们。幸运的是，MKSnapshot 有一个方便的point(for:) 方法可以将快照中的CLLocationCoordinate2D 转换为CGPoint。

例如，假设您有一个 CLLocationCoordinate2D 数组：

private var coordinates: [CLLocationCoordinate2D]?

private func generateImageFromMap() {
    guard let region = mapRegion() else { return }

    let options = MKMapSnapshotter.Options()
    options.region = region
    options.size = CGSize(width: 200, height: 200)
    options.showsBuildings = false
    options.showsPointsOfInterest = false

    MKMapSnapshotter(options: options).start() { snapshot, error in
        guard let snapshot = snapshot else { return }

        let mapImage = snapshot.image

        let finalImage = UIGraphicsImageRenderer(size: mapImage.size).image { _ in

            // draw the map image

            mapImage.draw(at: .zero)

            // only bother with the following if we have a path with two or more coordinates

            guard let coordinates = self.coordinates, coordinates.count > 1 else { return }

            // convert the `[CLLocationCoordinate2D]` into a `[CGPoint]`

            let points = coordinates.map { coordinate in
                snapshot.point(for: coordinate)
            }

            // build a bezier path using that `[CGPoint]`

            let path = UIBezierPath()
            path.move(to: points[0])

            for point in points.dropFirst() {
                path.addLine(to: point)
            }

            // stroke it

            path.lineWidth = 1
            UIColor.blue.setStroke()
            path.stroke()
        }

        // do something with finalImage
    }
}

然后是以下地图视图（坐标，如MKPolyline，由mapView(_:rendererFor:) 渲染，像往常一样）：

上面的代码会创建这个finalImage: