Method of determining a principal portion of an image and method of determining a copying condition

A method of determining a principal portion of an image, comprising the steps of:

• extracting, from an identical original image, regions estimated to correspond to a principal portion thereof, respectively, by means of a plurality of mutually different extracting methods for extracting from an original image a region estimated to correspond to a principal portion thereof, and evaluating said extracting methods by comparing with respect to a plurality of original images, on the one hand, the regions estimated to correspond to the principal portion and extracted respectively from the identical original image by said extracting methods and, on the other hand, a region corresponding to the principal portion of the identical original image, or a region having a high probability of being a region corresponding to the principal portion of the identical original image and determined on the basis of the regions estimated to correspond to the principal portion and extracted respectively by said extracting methods;
• setting in advance a priority with respect to each of said extracting methods in correspondence with a result of evaluation;
• extracting a region estimated to correspond to a principal portion from an original image from which the principal portion is to be extracted, by an extracting method of a high priority;
• determining a region having a high probability of being a region corresponding to the principal portion of the original image, on the basis of a result of the extraction by the extracting method of the high priority;
• extracting further a region estimated to correspond to the principal portion from the determined region, by an extracting method of a low priority;
• and
• determining again a region having the high probability of being the region corresponding to the principal portion of the original image, on the basis of a result of the extraction by the extracting method of the low priority.