Data compression for gray images using Hubert scan

The Hilbert curve is one of the space-filling curves proposed by Peano. It has various applications such as image processing and computer holograms. The Hilbert curve fills each quadrant obtained by recursive quad-division of a plane (like "single-stroke writing") so that the curve always goes to an adjacent quadrant. This paper proposes a technique of nonreversible data compression of a gray image, which is an improvement over the author's previously published paper using a quad-tree representation. The proposed method transforms a gray image to a one dimensional signal with high neighborhood preservation, using a simple approximation for straight-line segmentation. The experimental results confirm that the method at about 0.6 bit/pixel produces almost the same visual image quality as JPEG.