1. An image categorizing apparatus, comprising: an edge detection module, for performing an edge detection operation on a plurality of pixels of an image so as to generate edge information corresponding to the image, wherein the edge detection module is embodied at least partially in tangible circuitry; and a statistics module, for performing a detection window based statistics operation on the edge information so as to generate statistics information corresponding to the image, wherein the statistics module is embodied at least partially in tangible circuitry and further operates to use a plurality of pixels of a specific detection window as statistical objects, in order to calculate categorized pixel numbers of each kind of edge in the specific detection window and then further categorize a specific pixel according to the statistical result.