code: public void texSubImage2D(Image image, int target, int level, int xOffset, int yOffset, int format,
                              int type) {
      throw new UnsupportedOperationException();
    }
docs: See http://www.khronos.org/opengles/sdk/docs/man/xhtml/glTexSubImage2D.xml
  
  <p>The default implementation is based on {@link Image#getRgb} and will hand over a RGBA byte
  array. Please set the (internal)format and type parameters accordingly; they are mainly
  present for future support of different formats. The WebGL implementation will pass through
  all parameters.</p>