Render a Map to an image

[lucas.werkmeister]

Hello everyone,
I need to get an image from a Map (Windows Phone 8), to use it for a live tile. This is what I have so far:

const int imgSize = 210;
Map tempMap = new Map { Width = imgSize, Height = imgSize };
// ... adding some layers, setting the view
Size size = new Size(imgSize, imgSize);
tempMap.Measure(size);
tempMap.Arrange(new Rect(new Point(0, 0), size));
tempMap.UpdateLayout();

WriteableBitmap bmp = new WriteableBitmap(imgSize, imgSize);
bmp.Render(tempMap, null);
bmp.Invalidate();
IsolatedStorageFile store = IsolatedStorageFile.GetUserStoreForApplication();
string filename = "/Shared/ShellContent/" + /* ... file name */ ".jpg";
using (IsolatedStorageFileStream stream = store.OpenFile(filename, FileMode.OpenOrCreate))
    bmp.SaveJpeg(stream, imgSize, imgSize, 0, 100);

tile.Update(new FlipTileData
{
    // ... set other properties
    BackgroundImage = new Uri("isostore:" + filename, UriKind.Absolute)
});

As you can see, the map that I render is never part of the visual tree. I gather from several places (stackoverflow, msdn) that this should not be a problem; unfortuately, the image is simply black.
Is something wrong with my code, or might this be a bug with the Nokia Map?

[symbianyucca]

I don't think that the WP8 API would be designed for the map to be saved into image. anyway, there is HERE API for the purpose, its called Map Image API: http://developer.here.com/rest_api

[lucas.werkmeister]

Will this work for not-Nokia phones as well? I don't want my app to be Nokia-exclusive...

EDIT: I also asked on stackoverflow, link

[symbianyucca]

it would work, it is basically HTTP query, thus not really even OS specific.