feature request: {#} with leading zeroes

[Thomas Sattler]

There is an example for {#} in the manpage. Its description says,
it might be "useful for making input PNG's for ffmpeg":

|
| find . -type f | sort | parallel convert {} {#}.png
|

I'd guess that it wouldn't work with ffmpeg, as the images would
be sorted like this:

  10.png 11.png 12.png [...] 18.png 19.png 1.png [...]

Wouldn't it be usefull to have sequence numbers with leading
zeroes here?

I know that parallel doesn't know the number of images to
rename and so it cannot find the number of leading zeoes
on its own, but maybe there could be a commandline
switch for {#}'s (minimum) arity?

Thomas