Assumptions for Polygon or Area Clipping Algorithm
Assumption: The viewport and window are rectangular. So only, by identifying the maximum and the minimum coordinates that is, (Xw_{max}, Yw_{max}) and (Xw_{min}, Yw_{min}) we can explain the size of the overall viewport or window.
Viewport and Window are unlimited to only rectangular shapes they could be of any other shape that is Convex or Concave or both.
For good understanding of the clipping conception refer to following figure:
Figure: Clipping with Viewing Transformation through rectangular viewport and window