Another way in corel
Under window/dockers,, select bitmap color mask
using eyedropper under this bitmap color mask window (not the eyedropper on the left toolbar) select the color you want out.. Set the tolerance and click apply...
OR to do a Power clip...
Select the object in the case a circle...
Select the image, right click then drag it to the object. a bomb sight will appear. release r click and a menu will pop up. select powerclip inside..
If your graphic does not look right in the powerclip you can change the settings under..
tools/options/edit
select or unselect "autocenter new powerclip contents"