'Return tile URLs that start with file://, by first retrieving them.'

def getTileUrls(self, coord):

    if (self.threadsafe or self.lock.acquire()):
        (mime_type, tile_data) = TileStache.getTile(self.layer, coord, 'png', self.ignore_cached)
        (handle, filename) = mkstemp(prefix='tilestache-compose-', suffix='.png')
        write(handle, tile_data)
        close(handle)
        self.files.append(filename)
        if (not self.threadsafe):
            self.lock.release()
        if self.verbose:
            size = (len(tile_data) / 1024.0)
            printlocked(self.lock, (self.layer.name() + ('/%(zoom)d/%(column)d/%(row)d.png' % coord.__dict__)), ('(%dKB)' % size))
        return (('file://' + abspath(filename)),)
