Question : Alpha overlay in Illustrator

Fireworks has a neat feaure where you can take a bitmap and set a filter 'Convert to Alpha' such that it becomes a transparent greyscale.  You can then put this image over the top of another coloured component such that it picks up the underlying colour.  Does anyone know whether it's possible to do the same in Illustrator?

Answer : Alpha overlay in Illustrator

Select the bitmap and (using the transparency pallete -- to show it: shift+F10):

- select the way you want it to interact with undelying objects (multiply, screen, overlay... etc) -- if necessary use (with the bitmap selected) Filters->Colors->Convert to Grayscale.

- or, shift-select also the object (or group of objects, doesn't matter -- just be careful that the bitmap stays on top) that should be influenced and click the arrow in the upper right corner of the transparency pallete, and in the menu that appears choose "Make opacity mask".