JPEG-LS standard is a context-based lossless image compression scheme, which uses 180° type modeling contexts in one pass scanning of an image. In this paper, for capturing high-order dependencies, statistical features and spatial configuration of an image, the three-pass JPEG-LS scheme with 360° type modeling contexts is proposed. For context determination, local gradients of intensity capturing the level of activity (smoothness, edginess) surrounding a pixel, is employed. For images with small dimensions, three-pass scheme and for large dimensions one-pass scheme result in higher compression ratios.
