Config is the global color table (palette), width and height. A nil or empty-color.Palette Config.ColorModel means that each frame has its own color table and there is no global color table. Each frame's bounds must be within the rectangle defined by the two points (0, 0) and (Config.Width, Config.Height).

For backwards compatibility, a zero-valued Config is valid to pass to EncodeAll, and implies that the overall GIF's width and height equals the first frame's bounds' Rectangle.Max point.