1. A daytime and nighttime image recognizing method, comprising: inputting an image captured by a camera apparatus; predefining an air region and a terrestrial region for the input image captured by the camera apparatus; calculating a lightness value histogram for the air region of the input image; determining a lighting condition of a photo environment of the camera apparatus based on the lightness value histogram for the air region of the input image, wherein determining the lighting condition further includes: judging whether a ratio of a number of pixels with lightness values larger than a first lightness value (T1) in the air region of the input image to the total number of pixels in the air region of the input image is greater than a first ratio; and determining the photo environment of the camera apparatus as a daytime lighting condition if the judgment result is affirmative; and wherein calculating the lightness value histogram and determining the lighting condition require no vehicle lane lines in the input image.