The invention relates to a method for determining the power of an electric motor for driving a hybrid compressor of an air-conditioning circuit of a motor vehicle having a heat engine during phases in which the drive of the hybrid compressor by the heat engine is interrupted. A preferred embodiment of the method is for use with networked printers. A specific area of interest of the captured image can be defined on the display device by zooming and panning or by defining a window over the captured image, and a histogram derived from only that area of interest can be displayed. The bladder may be controllably deformed to seal against a tool string passing through the device using an inwardly directed pressure, which preferably is exerted by a fluid in the interstitial space between the spool and the bladder.