The University of British Columbia

Exact bi-level image expansion techniques are required for a wide range of applications such as cartography, calligraphy, medical images, remote sensing, and satellite imagery. Among the methods proposed in the literature are (a) pixel replication; (b) area sizing; (c) interpolation and spline methods; and (d) DCT-based techniques. All these methods generate distortion and noticeable degradation in the quality of images especially around edges. We introduce a new image expansion scheme that produces significantly improved expanded and/or reduced images and maintains high quality edges. This scheme uses an elaborate look-up table that is based on look-ahead-and-back procedures for each pixel and maintains a memory of the pixels' chain code connectivity. The experimental simulation results show that the resized images of the proposed scheme are aesthetically and objectively much better than those of the other methods.