A contour-based approach to image compression

Abstract

This paper presents an alternative spatial image compression method that can be directly applied to compressing certain classes of grey-scale and/or colour (RGB, 24 bits) imagery of any size. The process involves the vectorisation of digital images into contour maps with subsequent converting of the contours to a pixel format. Contours are often approximated by polygons (linear or otherwise), and only the vertices of the polygons need to be retained to recreate the original contour lines. The final amount of storage depends crucially on the complexity of the image and on the degree of approximation desired. In this context, the compression process is based on filtering and eliminating those contours that may contain redundant information. Contours extracted from digital images may contain multiple redundant data (i.e. intersecting or nested contours), any of which might logically be used as a basis for discrimination and/or used in the reconstruction of an original captured image. Depending on the applications, and the amount of contour lines employed in the reconstruction of an image, the process allows for various levels of image accuracy while preserving visual integrity and reducing compression artefacts. The proposed method does not require special hardware and, if combined with existing encoding schemes, can be efficiently used for image transmission purposes.