Texture controlled particle emission?

I’m trying to get this to work (scroll down to bottom) -

http://www.blender.org/cms/New_Particle_options_a.721.0.html

but, no luck so far. My map is white except for a black corner, but the particles emit evenly. Can someone who knows how look at my .blend file?

Link

I think this would be fantastic for getting particle hair to line up with a hair line.

Well from what I can tell, UV coordinates don’t work. Not sure if this is a bug, or a limitation. Check out my version:
http://schnellweb.ca/blender/texemit.blend

In the particle panels, you have to ensure that texemit is pressed, and linked to the right texture, as well as the tex force channel and Z amount. you can control your hair length with the texture velocity variable, the Z force amount, or the contrast of your texture. Works great for non uv mapped images, as well as procedural. If anyone knows how to get UV mapped textures to emit, let us know.