On the use of splines in hierarchical image transmission

A quick identification of the received image is a desirable feature in low bandwith transmission systems. A gross quality approximation of the image is obtained at early stages when it is hierarchically encoded. This allows faster recognition than raster scanning methods, without transmission overhead. Spline interpolation facilitates this process, greatly improving the efficiency of hierarchical approaches. The same subjective impression is obtained with half of the information. Cubic convolution interpolation has all the advantages of the former, and can be more easily calculated. Recognition with less amount of received bits can be achieved with a non uniform development of the hierarchy. In order to automatize this procedure, two algorithms are presented with their advantages and drawbacks. In all the considered cases, transmission can be ended when the receiver decides. So, compression can be achieved at the cost of an approximation errors.