UI selected transform question

[Casper Boemann]

I'm fiddling with recoding scaling,rotating and shearing.

Apart from doing it with integer math and multipass algorithms I also want to 
take selections into account.

Regarding selection. The code is easy enough, but how do we let the user scale 
in a GUI manner:

When you have selected a rect in a traditional paint app. it's easy enough 
simply drag the corners.

But when you have selection that is a bitmap, then how do you present the user 
with an intuitive GUI.

A simple slider is not good enough because it doesn't offer the fine control 
down to a single pixel as users would want. Think of a scale to 3 times 
original size  plus 3 pixels (to eg match a feature in an underlying layer).

do you get the problem and any ideas?

-- 
best regards / venlig hilsen
Casper Boemann