code: public BufferedImage render(List<ColouredPolygon> entity)
      {
          // Need to set the background before applying the transform.
          graphics.setTransform(IDENTITY_TRANSFORM);
          graphics.setColor(Color.GRAY);
          graphics.fillRect(0, 0, targetSize.width, targetSize.height);
          if (transform != null)
          {
              graphics.setTransform(transform);
          }
          for (ColouredPolygon polygon : entity)
          {
              graphics.setColor(polygon.getColour());
              graphics.fillPolygon(polygon.getPolygon());
          }
          return image;
      }
docs: Renders the specified polygons as an image.
  @param entity A collection of coloured polygons.
  @return An image object displaying the polygons.