How to draw a CLLocationCoordinate2Ds on MKMapSnapshotter (drawing on mapView printed image)

Question

I have mapView with array of CLLocationCoordinate2D. I use these locations to draw lines on my mapView by using MKPolyline. Now i want to store it as a UIimage. I found that theres class MKMapSnapshotter but unfortunately i can't draw overlays on it "Snapshotter objects do not capture the visual representations of any overlays or annotations that your app creates." So i get only blank map image. Is there any way to get image with my overlays?

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...
        }
    }
}

How can i put overlays on this image? Or maybe theres other way for that problem.

Answer 1

Unfortunately, you have to draw them yourself. Fortunately, MKSnapshot has a convenient point(for:) method to convert a CLLocationCoordinate2D into a CGPoint within the snapshot.

For example, assume you had an array of CLLocationCoordinate2D:

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
    }
}

Then the following map view (with the coordinates, as MKPolyline, rendered by mapView(_:rendererFor:), like usual):

The above code will create the this finalImage: