The aim of this work is to propose a new mathematical model for optimal contrast enhancement of a digital image. The main idea is to combine the Divide-and-Conquer strategy, and a reaction diffusion mathematical model to enhance the contrast, and highlight the information and details of the image, based on a new conception of the Sine-Cosine optimization algorithm. The Divide-and-Conquer technique is a suitable method for contrast enhancement with an efficiency that directly depends on the choice of weights in the decomposition subspaces. Methods: in this paper, a new algorithm has been used for the optimal selection of the weights considering the optimization of the enhancement measure (EME). Results: in order to evaluate the effectiveness of the proposed algorithm, experimental results are presented which show that the proposed hybridization technique is robustly effective and produces clear and high contrast images.