 public class AlphaGoogleMapsLayer : Layer
    {
        private GoogleMapsLayer googleLayer;
        public float Alpha { get; set; }

        public AlphaGoogleMapsLayer()
            : this(255)
        { }

        public AlphaGoogleMapsLayer(float alpha)
            : base()
        {
            googleLayer = new GoogleMapsLayer();
            Alpha = alpha;
        }

        public AlphaGoogleMapsLayer(float alpha, string licenseKey, string cacheDirectory)
            : this(alpha)
        {
            googleLayer.LicenseKey = licenseKey;
            googleLayer.CacheDirectory = cacheDirectory;
        }

        protected override void DrawCore(GeoCanvas canvas, System.Collections.ObjectModel.Collection<SimpleCandidate> labelsInAllLayers)
        {
            int canvasWidth = (int)canvas.Width;
            int canvasHeight = (int)canvas.Height;
            using (Bitmap bitmap = new Bitmap(canvasWidth, canvasHeight))
            {
                GdiPlusGeoCanvas gdiCanvas = new GdiPlusGeoCanvas();
                gdiCanvas.BeginDrawing(bitmap, canvas.CurrentWorldExtent, canvas.MapUnit);
                googleLayer.Open();
                googleLayer.Draw(gdiCanvas, new Collection<SimpleCandidate>());
                googleLayer.Close();
                gdiCanvas.EndDrawing();

                using (Bitmap newBitmap = new Bitmap(canvasWidth, canvasHeight))
                {
                    Graphics graphics = Graphics.FromImage(newBitmap);
                    Rectangle rectangle = new Rectangle(0, 0, bitmap.Width, bitmap.Height);
                    ImageAttributes imageAttributes = TranslateImage();
                    graphics.DrawImage(bitmap, rectangle, 0, 0, bitmap.Width, bitmap.Height, GraphicsUnit.Pixel, imageAttributes);

                    MemoryStream stream = new MemoryStream();
                    newBitmap.Save(stream, ImageFormat.Png);

                    GeoImage geoImage = new GeoImage(stream);
                    canvas.DrawScreenImageWithoutScaling(geoImage, canvasWidth * 0.5f, canvasHeight * 0.5f, DrawingLevel.LevelOne, 0, 0, 0);
                    stream.Close();
                }
            }
        }

        private ImageAttributes TranslateImage()
        {
            // noramlize the color components to 1 
            float r = 0 / 255;
            float g = 0 / 255;
            float b = 0 / 255;
            float a = Alpha / 255.0f;

            float[][] floats = new float[5][];
            floats[0] = new float[] { 1, 0, 0, 0, 0 };
            floats[1] = new float[] { 0, 1, 0, 0, 0 };
            floats[2] = new float[] { 0, 0, 1, 0, 0 };
            floats[3] = new float[] { 0, 0, 0, a, 0 };
            floats[4] = new float[] { r, g, b, 0, 1 };
            ColorMatrix ColorMatrix = new ColorMatrix(floats);

            ImageAttributes imgAttributes = new ImageAttributes();
            imgAttributes.SetColorMatrix(ColorMatrix);

            return imgAttributes;
        }
    } 