For those of you who are interested in programming, here are a few technical details
Rubber Dub-Dub is written in Visual Basic, which is not normally used for graphics programs. This is largely on account of VB's "Point" and "PSet" instructions for reading and plotting pixels, which are far too slow. Although these instructions are used in some places in RD-D, the program also makes use of an advanced non-standard "pointer" technique which makes it possible to read or plot the pixels by direct access to the picture's bitmap in memory. Consequently, the reading or plotting of pixels becomes up to 15 times faster. This makes the program truly "viable" in VB.
However, since Windows does not appear to contain appropriate API routines for converting back and forth between RGB and HSL, these rather hefty calculations tend to slow down the plotting of pixels even further. This situation is alleviated by the provision of the "rubber.dll" for the calculations which makes a difference of about 15%.
Whether or not there will be future versions of Rubber Dub-Dub depends on the public's response to the first version. Certainly, if a favourable response should occur, techniques for even greater agility will be sought.