Variation of JPEG-LS to low cost rate control and its application in region-of-interest based coding

摘要

JPEG-LS is the latest pixel based lossless (LS)/near-lossless (NLS) still image coding standard introduced by the joint photographic experts group (JPEG). Since the introduction of this standard, several improvements, variations and applications to the original algorithms have been proposed in literature (IEE Electron. Lett. 37 (22) (2002) 1327; Proc. of IASTED Int. Conf. on Visualization, Imaging and Image Processing, VCIP 2001, Marbella, Spain, 2001, p. 340; IEE Trans. Cons. Elec. 3 (3) (2001) 466; IEE Proc.: Vision, Image Signal Process. 147 (6) (2000)). While JPEG-LS introduces a constant information loss by using a single pre-determined compression parameter NEAR, previously, attempts have been made to redistribute the information loss by using a context dependent, three-parameter scheme, which is aimed at improving the subjective image quality of the reconstructed images. In this paper we extend this work to rate controlled image compression and region-of-interest (ROI) based coding, thereby extending JPEG-LS standard's use to a wider digital imaging application area. We show that the proposed rate-control scheme outperforms previously published work in applying JPEG-LS to low cost rate control, in terms of algorithmic and computational complexity, accuracy of achieving the target compression ratio, range of performance, subjective image quality and objective rate-distortion performance. Finally we propose the application of the above rate control scheme in ROI based coding.