1. An image processing method, comprising: converting a to-be-processed image into a gray image; performing Gaussian blur processing having a predefined blur radius on the gray image, and obtaining a reference image; and according to gray values of reference pixels of the reference image, decreasing a pixel value of a pixel of a copy of the to-be-processed image corresponding to a reference pixel whose gray value is larger than a gray threshold, increasing a pixel value of a pixel of the copy of the to-be-processed image corresponding to a reference pixel whose gray value is smaller than the gray threshold, and obtaining an adjusted image, wherein the predefined blur radius is positively correlated to at least one of the number of row pixels of the to-be-processed image and the number of column pixels of the to-be-processed image.