1. An automatic film recognition method for recognizing a film in a scanner, comprising the steps of: (a) previewing the film using the scanner to obtain an original preview image comprising a film image corresponding to the film, wherein the original preview image comprises pixels and each pixel has a first hue value, a second hue value, and a third hue value; (b) selecting the pixels with luminance in a predetermined range from the original preview image to acquire a second preview image; (c) framing the second preview image according to the first hue values of the pixels to obtain an image frame; and (d) sectioning the image frame to recognize the film image.