Converting Image to bitmap turns background black

I need to convert an Image to a bitmap.

initially a gif was read in as bytes and then converted to an Image.

But when I try convert the image to a bit map, the graphic displaying in my picturebox has a black background when it used to be white.

Here is the code:

    var image = (System.Drawing.Image)value;
        // Winforms Image we want to get the WPF Image from...
        var bitmap = new System.Windows.Media.Imaging.BitmapImage();
        bitmap.BeginInit();
        MemoryStream memoryStream = new MemoryStream();
        // Save to a memory stream...
        image.Save(memoryStream, ImageFormat.Bmp);
        // Rewind the stream...
        memoryStream.Seek(0, System.IO.SeekOrigin.Begin);
        bitmap.StreamSource = memoryStream;
        bitmap.EndInit();
        return bitmap;

Can some one explain why the background is going black and how i can stop it doing this.

Thanks