Constructs a display object that can display grid objects that have
a pictureIcon method.
public void draw(GridObject obj,
Draws a unit-length object using an image.
This implementation draws the object by scaling
the image provided to the constructor. It calls
the adjust method to make further
adjustments (for example, rotating and tinting
the image) as appropriate.
(Precondition: obj has a pictureIcon method.)