The standard wavelet transform fails to provide an efficient representation due to the spatial isotropy of its basis functions built in the horizontal and vertical directions.In this paper

Directionlet based compression scheme was proposed .Using improved octree segmentation to adaptively partition an image into the smaller segments with a dominant direction.Directionlet is applied on a geometrical regular segment

whose optimal geometrical directions constitute the generator matrix of Directionlet transform

coding the coefficients and directional information respectively.Application of Directionlet transform along the optimal geometrical direction per segment efficiently improves sparse representation for image and enhances the coder performance.Experiments demonstrate the superiority of the proposed approach when compared to the wavelet-based SPIHT and JPEG2000 both in terms of objective compression performance measurements as well as visual quality

especially for those images with geometrical regular features.