Reversible binary image data hiding by run-length histogram modification

A novel reversible binary image data hiding scheme using run-length (RL) histogram modification is presented in this paper. The binary image is scanned from left to right and from top to bottom to form a sequence of alternative black RL and white RL. Combining one black RL and its immediate next white RL, we form one RL couple, thus generating a sequence of RL couples. The length of each couple is fixed during data embedding in order not to fail the reversibility. Two procedures are adopted to achieve reversibility: (1) only involve those RL couples in data embedding in which the length of couple is not shorter than threshold T1; (2) increase white RL of isolated white pixels from one to two. Another parameter T indicates where to embed data in black RL histogram. Adjusting T1 and T may result in optimum performance of pure embedding rate versus visual quality of marked image. The proposed scheme works for text, graphics, and their mixture, both halftone and nonhalftone binary images. Experimental works have shown its superior performs over the prior-arts.