In a method for processing an image file using a computing device, an image file from a storage system is read. If an image in the image file is slanted, an incision coordinates according to a configuration file in the storage system and a preset formula is calculated. The method incises the image using the calculated incision coordinates and storing the incised image in a new image file. If an image in the new image file is not slanted, the method further determines whether the image has been incised. If the image has been incised, the method records the calculated incision coordinates that make the image not be slanted as optimal incision coordinates, and stores the optimal incision coordinates into a database.