Abstract: An image processing module for processing a digital M-level input image into a digital N-level output image is provided, wherein M>N and N>2, a level being indicative of a colorant density in a printing process. The module applies N-1 thresholds for determining an output level for each image element with an input level, wherein thresholds associated with a transition between two output levels are arranged in a threshold matrix, all N-1 threshold matrices being arranged in accordance with a single basic threshold matrix arrangement. The image processing module comprises threshold matrices, wherein the thresholds have been adjusted to compensate printed density variations except the thresholds associated with a transition between a first and a second level, which have not been adjusted in order to keep a number of colorant receiving print positions constant.

Abstract: In a printer having a print head moveable relative to a recording medium, the recording medium and print head may touch each other, thereby possibly damaging the print head and/or the recording medium. In order to prevent further damage, it is advantageous to detect a medium touch as soon as possible. An available feedback signal relating to the print head, e.g. originating from a carriage on which the print head is mounted, is employed to determine whether a medium touch has occurred such that a dedicated medium touch or crash sensor may be omitted. A malfunctioning nozzle signal is used to determine a change in a number of malfunctioning nozzles to detect a medium touch. Alternatively, a print head position signal is used to determine a position error and derive from the position error whether or not a medium touch has occurred.

Abstract: In a printer having a print head moveable relative to a recording medium, the recording medium and print head may touch each other, thereby possibly damaging the print head and/or the recording medium. In order to prevent further damage, it is advantageous to detect a medium touch as soon as possible. An available feedback signal relating to the print head, e.g. originating from a carriage on which the print head is mounted, is employed to determine whether a medium touch has occurred such that a dedicated medium touch or crash sensor may be omitted. A malfunctioning nozzle signal is used to determine a change in a number of malfunctioning nozzles to detect a medium touch. Alternatively, a print head position signal is used to determine a position error and derive from the position error whether or not a medium touch has occurred.