[chimera-dev] Divided the Volume Data into two parts

Hello, I would like to divided a density map (volume data) into two parts. For example, the size of the whole density map is 320*320*320. I want to get one part which covers the region from (i,j,k) to (x,y,z), e.g. from (0,0,0) to (100,100,100). The rest is the other part. The transparency for the first part is 0 and for the second part is 0.5. And I still want to get the histogram of the first part. How could I achieve this in a python script? Actually, I want to get the histogram of different regions. I plan to run a loop for different regions (Change the (i,i,k) and (x,y,z) for the first part). Could I save all of the histograms in one file which is not a window of the Chimera but a picture. Best, Huiya