Hi Ravi,
Raster Manager is using DrawTiledRaster, mentioned by Jon, instead of DrawRaster to do the drawing. Unfortunately the Raster::TiledRaster struct doesn`t seem to be available in the SDK, so there is no way for you to use it (I`ll check with one of my colleague to see if this is the case).
So the alternative would probably be, as Jon said, to use mdlRaster. One workflow would be to create temporary image file whose pixels have been processed as you which and attach this image file to Raster Manager.
Thanks,
Mathieu