Make 2 (4? 10?) discrete luminance levels in Aperture?

Question

Hi. Tonight's puzzler. Is there any way, using Aperture, to create a luminance map of an image which maps every pixel to a luminance bin? At its simplest, this would take an image and reduce it to black & white (not Grayscale) -- two bins -- where every pixel above a certain luminance (user settable preferred) would be colored white (luminance = 100%) and every pixel at or below that certain luminance would be colored black (luminance = 0%).
Even at that level I could make good use of such a tool (as long as the dividing line is movable), but I really want something which maps the image to more discrete steps. The Munsell system uses ten levels, which would be good. I would be equally happy with five.
There are ways to set the Levels Brick to give four (or six) steps from a grayscale image (make a "V" or an "M" or a "W"). This is a fairly kludgy work-around, though. I've set up five different Adjustment pre-sets for different "binnings". In use it is inelegant and impractical. I have tried using multiple Levels Bricks with different Brush Ranges. Sad to report, applying this as a saved pre-set repeatedly brought Aperture to its knees.
If there are other programs which can do this with aplomb (I don't know much about Photoshop), please point me in the right direction. This is just one of several more-or-less metrical image analyses I am essaying.
As always, thanks!

Answer 1

Keith Barkley wrote:
Continuing the PhotoShop idea:
There is a plug-in (or there used to be!) called "filter factory" which would let you create filters using expressions that would apply to every pixel in the image. The expressions look soemthing like this:
r: if (r < 128)?0:r
g: if (g < 128)?0:g
b: if (b < 128)?0:b
which would set each component to 0 if it is less than a value of 128.
Of course, it is much more versatile than this, it would be pretty easy to do what you want with this tool.
<a class="jive-link-external-small" href="http://">http://www.creativemac.com/2002/02_feb/tutorials/filterfactorycomplete2.htm
Exactly! Exactly what I am looking for. Your link is from 2002, and I can't find any up-to-date information. Do you know if Filter Factory is still available? Has the functionality (writing expressions which are applied to each pixel) been incorporated into the current version of Photoshop?
One of my frustrations with Aperture is that, although the Bricks are the equivalent of sophisticated transform functions operating on each pixel, Aperture neither specifies what the functions are, nor lets one modify them. (I would be ecstatic if something like Filter Factory were available for Aperture.)
For instance, the Vibrancy parameter is defined in the Help file this way:
+The Vibrancy parameter applies saturation to the image in a nonlinear manner. Colors that are already saturated are left alone, while saturation is added to all other colors. In addition, the Vibrancy parameter takes skin tones into account, leaving them untouched.+
That is good to know, but incomplete. It suggests, but doesn't specify, the shape of the non-linear curve (two curves, actually -- one for saturation and another for hue). I could make much use of the knowledge of the parameters' explicit definitions. And I could I dance downtown if we were provided sliders to change the definitions.
Maybe Aperture 5.x.