Comment 6 for bug 171589

>Having said that being very specific about the features you
want should make things easier for developers, especially if
you can break things down into smaller more managable chunks.

I don't think it can be broken down to be any more specific
or in smaller chunks. :) These color tools are very common
and have a very specific use, so I don't think there would
be any confusion about what they are susposed to do or how
they are susposed to work.

It requires the following steps:

1) Gather all color values (fill, stroke, and gradient keys)
from the selected objects.

2) Send the values to be manipulated by a color tool.

3) The color values are manipulated the same way pixel color
values are manipulated in raster programs. (The only
difference I can think of is if you are working with a
restricted color pallet, the color values would need to be
"snapped" to the closest value available in the pallet)

4) The display is updated in real time so that the changes
can be previewed

5) If accepted, the new color values are applied to the objects.

6) There can be all kinds of color tools eventually created,
but the most important are: Hugh-Saturation,
Brightness-Contrast, Curves and Levels. (GIMP provides a
good source code reference for this functionality)