A sketch processing system is described herein for assisting a user in producing a drawing. In one implementation, the sketch processing system operates by: receiving ink strokes in response to creation of an original drawing; recognizing components and geometric constraints within the original drawing, to produce a recognized drawing; beautifying the original drawing by modifying at least one aspect of the recognized drawing in accordance with the recognized constraints, to produce a beautified drawing; and recognizing a recurring pattern in the beautified pattern (if any) and using that pattern to produce at least one added component to the beautified drawing.