In this paper, we propose a new method for representing gray level image by two-tone. In our proposed method, the whole area is divided into the blocks composed of 2 × 2 pixels, and determined a total value of pixels in each block. Secondly, the value is divided into the blocks composed of the maximum pixel value. The quotient means the number of white dots. The position of the white dots is decided by the order of pixel value. The rest is saved for the next process. Then, neighbor 2 × 2 blocks are merged and the above-mentioned distribution process is recursively applied. Thus, the position of white dots is progressively determined, that is to say, this algorithm works as bottom-up process. In addition, we consider improvement of our proposed method. As a result, our proposed method outperforms the Multistage Division Quantization method ( MDQ ) in the gradation region.
View full abstract