1. A method implemented by a computing device, the method comprising: calculating, for candidate croppings of a scene, scores indicative of a boundary simplicity for each of the candidate croppings, including: ranking the candidate croppings according to values derived for the candidate croppings that indicate a complexity of the scene along a boundary of a candidate cropping, and calculating the scores indicative of the boundary simplicity as normalized scores for the candidate croppings based on the ranking; and choosing one or more croppings from the candidate croppings based, at least in part, on the scores calculated for the candidate croppings that are indicative of the boundary simplicity.
2. A method as described in claim 1 , wherein calculating the scores indicative of the boundary simplicity includes: measuring the complexity of the scene along the boundary of each respective cropping of the candidate croppings to derive the values indicative of the complexity.