Dead nozzle compensation

A controller for a printhead is provided. The printhead has rows of printing nozzles with each nozzle row formed by adjacent sub-rows of printing nozzles of adjacently disposed printhead modules. Each nozzle row us arranged such that the join of the respective adjacent sub-rows is arbitrarily located relative to the other nozzle rows thereby forming an arbitrarily shaped join region. The controller being configured to determine the arbitrary shape of the join region and to supply dot data to the printhead which compensates for the determined arbitrary shape.