1. An image processing method, comprising steps of: generating a first scale binary image from an image, wherein the first scale is smaller than the original scale of the image; detecting at least one text line in the image based on the first scale binary image; generating a second scale binary image from the image, wherein the second scale is larger than the first scale; for each text line, calculating a similarity between a corresponding section in the first scale binary image and a corresponding section in the second scale binary image, and removing the text line for which the similarity is lower than a predetermined level as noise; for one or more of the remaining text line(s), performing optical character recognition on corresponding section(s) in the second scale binary image to determine character orientation(s) of corresponding text line(s); and determining the orientation of the image according to the character orientation(s).