Bitmap example

Create a bitmap mask (segment 2) which is true (1) everywhere channels 1 and 2 are less than 25. Then this mask, and the mask in segment 3 are used to determine a region that should be zeroed in image channels 1 and 2.

if( %1 < 25 and %2 < 25 )then
  %%2 = 1
else
  %%2 = 0
endif
if( %%2 = 1 and %%3 = 0 )then
  %1 = 0
  %2 = 0
endif