Note that, in one operation, it is possible to both compress an image and extract a small part of the compressed image.
im> imcopy ``xdata$rp110590.qp[block=10][683:702,929:948]'' rp90_ac.imh
The coordinates used are the compressed or blocked coordinates, i.e.\ 6830/10=683, etc.
To limit the range of pulse heights included, the first square brackets should contain e.g. [block=10,pi=7:21].