Apply Run-length encoding on pixel differences to do image hiding

In 2011, Chen used Run Length Coding to record the repetition times of continuous data with the same value. These recorded data were then embedded in cover images by Module-based Substitution. In order to increase the quantity of repetition times of the data with the same value, in this paper, the pixel values are changed into difference values by using Median Edge Predictor (MED). The range of all possible difference values is subsequently divided into two regions. The difference values in the regions are reassigned new positive values, put through Run Length Coding, and embedded into cover images by Modulebased Substitution. According to the experimental results, the quality of the embedded image in the proposed method is better than that in Chen´s method.