COMPUTER GRAPHICS METAFILE CODING EFFICIENCY.

A previously published paper on 'Implementation and Comparison of Different Presentation Layer Codings for Efficient Transfer of GKS Metafiles' finds a 237 percent difference in coding efficiency between ECC (Erlangen Character Coding) and VDM (Virtual Device Metafile Character coding). We would not expect the difference to be that great, as the two coding techniques are really quite similar. Using several vector-oriented graphics files we compare the ECC and VDM coding techniques for the point list parameters of polylines. For each file, we counted the bytes used to code those point lists according to the ECC and VDM coding schemes. It is found that the VDM coding is indeed less efficient than the ECC coding, although not as inefficient as claimed. The VDM coding can be tuned to be more efficient by changing the coding of real coordinates in the way outlined.