Subpixel reconstruction of line drawings: a tree searching approach

An algorithm for reconstruction of line drawings from their chain codes is presented. A variation of the (M-L) algorithm called the M, L, δ algorithm is used for suboptimal searching. This algorithm requires a priori knowledge of the source statistics. It is assumed that the line drawing to be encoded is a smooth curve, with curvatures at a set of sample points along the curve forming a first-order autoregressive source. This algorithm, when used on curves of different variances, was found to work well, yielding low reconstruction distortion. Surprisingly, the algorithm was found to work well for arbitrary curves. This algorithm achieves significant reduction in bit rate without significant increase in distortion. For a given bit rate the proposed algorithm compared favorably with existing methods