public void setTransparent(int color) {
        transparent = color;
    }
Sets the transparent color for the last added frame and any subsequent
frames. Since all colors are subject to modification in the quantization
process, the color in the final palette for each frame closest to the given
color becomes the transparent color for that frame. May be set to null to
indicate no transparent color.

@param color
         Color to be treated as transparent on display.
core/src/main/java/com/bumptech/glide/gifencoder/AnimatedGifEncoder.java