Effects > Rainbow: minor clean-up
Effects > Emboss: total rewrite

Next up in the "modernize old PD functions" category is Effects > Edge >
Emboss or Engrave.  The function has simply been renamed "Emboss", and
the engrave parameter has been worked into a variable "thickness"
setting (which can be positive for embossing, or negative for
engraving).

Angle and depth are now customizable as well, and of course base color
selection remains.  The pdFilterSupport class is used calculate
interpolated embossed pixel positions, for excellent quality regardless
of angle or distance.  It also ensure that pixels near image edges are
now handled much better than past versions.