1. An image processing method, comprising: performing a classifying of an input image into predetermined image categories based on a feature of a brightness histogram of the input image; and adjusting a brightness for pixels of the input image based on brightness weighting functions corresponding to a result of the classifying of the input image and respective positions of the pixels, such that a classification of the input image into one of the predetermined image categories controls the adjusting of the brightness for the pixels of the input image through application of a corresponding brightness weighting function for that one predetermined image category.