Is this possible? To emit only from mapping of white on an object.
It is possible to work around it if the object has enough tessellation - simply add a Volume Select and put the Map in it to set soft selection by texture, then emit according to the vertex soft selection.
Another approach would be to use PRT Surface particles as seeds:
*Create a PRT Surface,
*Add a Magma modifier
*Set output to Selection channel
*Create an InputTexmap, set to Mono and pick the texture of the object.
*Connect the output of the InputTexmap to the second socket of a Subtract and connect that the Output node.
*Check “TextureCoord” as input and drag from it to create an InputChannel:TextureCoord - the PRT Surface acquires all mapping coords from the mesh, so if you have Channel 1 on the mesh, it will come over automatically.
*Drop a Krakatoa Delete on top and set to Delete By Soft-Sel and ID.
RESULT: You will have explicit particle distribution controlled by the texture map’s grayscale value. Use these particles to emit your Stoke particles. The beauty of this approach is that you can do ANY Magma tricks to cull/position/affect in any way the seeds before you start simming…
We have logged a wish for direct support of bitmaps, but it wasn’t top priority, so it did not make it into Beta 1.
Ah alright, I will give that a shot tomorrow. The PRT Surface seems a solid enough approach, thanks!
Perfect, now we’re cooking with gas! IMO I wouldn’t even worry about the map support in Stoke, this is everything and more. 
I hadn’t even gotten to use PRT Surface yet, in fact I haven’t been playing with the volcano lately and caught it on the release notes but simply forgot it was there!
Well, it’s a business decision thing. PRT Surface ships with Krak, so Stoke users might not have it.
Think about it - what would you do with Stoke particles if you don’t have Krakatoa? 
Stoke customers should install Krakatoa Evaluation - even loading the PRTs into PFlow would require it.
Unless they have Frost and are interested in meshing the particles…
You guys are seriously going to need to start bundling these things on a sales side.
I kinda hinted at this to Chris, he replied “I hate bundles” 
From a freelancer point of view they are wonderful from a studio point of view I think the developer gets the short end of the stick.
i’m listening!
cb