public void setSize(int w, int h) {
        if (started && !firstFrame)
            return;
        width = w;
        height = h;
        if (width < 1)
            width = 320;
        if (height < 1)
            height = 240;
        sizeSet = true;
    }
Sets the GIF frame size. The default size is the size of the first frame
added if this method is not invoked.

@param w
         int frame width.
@param h
         int frame width.
core/src/main/java/com/bumptech/glide/gifencoder/AnimatedGifEncoder.java