code: public Texture updateTexture () {
      if (texture == null || texture.disposed()) texture = createTexture(texconf);
      else texture.update(this);
      return texture;
    }
docs: Updates this image's default texture with the current contents of the image, and returns the
  texture. If the texture has not yet been created, then this simply creates it. This is only
  necessary if you want to update the default texture for an image associated with a {@link
  Canvas}, or if you have used {@link #setRgb} to change the contents of this image.