code: def image_coordinates(self, point):
          '''given a point in window coordinates, calculate image coordinates'''
          # the dragpos is the top left position in image coordinates
          ret = wx.Point(int(self.dragpos.x + point.x/self.zoom),
                         int(self.dragpos.y + point.y/self.zoom))
          return ref image_coordinates(self, point):
          '''given a point in window coordinates, calculate image coordinates'''
          # the dragpos is the top left position in image coordinates
          ret = wx.Point(int(self.dragpos.x + point.x/self.zoom),
                         int(self.dragpos.y + point.y/self.zoom))
          return ret
docs: given a point in window coordinates, calculate image coordinates