Images compression usually considers the minimization of storage space as its main advantage. It is desirable, however, to code images so that the ability to process the resulting representation directly is possible.
In this paper, a compression system based on Dictionary-Based compression methods is proposed for compressing images. The design and implementation of novel compression and decompression algorithm are described.
Dictionary-Based compression methods are a popular form of data file compression. LZ77, LZ78 and their variants are likely the most famous of these methods. These methods are implemented to reduce the one-dimensional correlation in data, since they are designed to compress text. Therefore, they do not take advantage of the fact that, in images, adjacent pixels are correlated in two dimensions. In this paper, a true two-dimensional dictionary-based lossless image compression scheme for grayscale images is introduced.
The proposed compression method and the compression system are examined using different images with different sizes. Good compression ratios have been obtained from the proposed system, and this depends on image nature. Comparisons between the proposed method and different methods is also given and the proposed algorithm gives better results than the other methods.
Testing results show that the compression performance of the proposed scheme outperforms and surpasses any other existing dictionary-based compression scheme. The results also show that it slightly outperforms JPEG-2000's compression performance, when it operates in its lossless mode, and it is comparable to JPEG-LS's compression performance, where JPEG-2000 and JPEG-LS are the current image compression standards. |