[Chimera-users] How to invert a map values in UCSF Chimera

Dear RBVI, I am currently looking into the ways to invert a map in UCSF Chimera so that I can flip the histogram of a map, but I cannot find a volume operation command that does the job. What command in UCSF Chimera allows creating a map with inverted map values? I thought it was vop but I cannot find a parameter that allows assigning negative value operation that would invert the map in UCSF Chimera command line documentation. Best, Junha Song.