Vectorising and feature-based filtering for line-drawing image compression

A three-stage method for compressing bi-level line-drawing images is proposed. In the first stage, the raster image is vectorised using a combination skeletonising and line tracing algorithm. A feature image is then reconstructed from the vector elements extracted. In the second stage, the original image is processed by a feature-based filter for removing noise in the objects out-line. This improves image quality and compression performance. In the final stage, the filtered raster image is compressed using a standard compression technique, JBIG. For a see of test images, the method achieves a compression ratio of 40:1, in comparison to 33:1 of JBIG.