Request additional flag for ImageGenerateRoIMask

Here is a sample code that shows the desired benefit.

// current approach to remove drawing that is not to be used in mask
// another option is to move the drawing to a different layer (e.g. Overlayer) and back to ProgFront
// could also repeat the steps on a group list gList

Function toggle_group(string wname, string gname)

	string gCMD = "DoWindow/F " + wname + ";SetDrawLayer ProgFront;DrawAction begininsert;"

	DrawAction/W=$wname/L=ProgFront getgroup=$gname, commands
	gCMD += ReplaceString("\r",ReplaceString("\t",GrepList(S_recreation,"^// ;*",1,"\r"),""),";")
	DrawAction/W=$wname/L=overlay getgroup=$gname, delete

	DoUpdate/W=$wname

// perform the image mask operation

	ImageGenerateROIMask/W=wname imageinstance

// return the removed drawing

	Execute/Z gCMD
	
	return 0
end

// desired approach

Function mask_onlygroup(string wname, string gname)

// perform the image mask operation

	ImageGenerateROIMask/W=wname/G=gname imageinstance
	
	return 0
end