Abstract: An image processing device includes: a first contamination detection circuit to detect contamination on an image reading device using a first relative threshold value calculated from a standard deviation of pixel values of a same-density region in a read image obtained by the image reading device, the image reading device reading a reference image formed on a recording medium by a line head including a plurality of inkjet heads and that has density regions of a plurality of gradations; a second contamination detection circuit to detect contamination on the image reading device using a second relative threshold value calculated from a standard deviation of pixel values of an area in the read image, the area being divided for each of the plurality of inkjet heads; and a contamination processing circuit to eliminate an influence of the contamination on the read image when at least one of the first contamination detection circuit or the second contamination detection circuit determines the contamination.

Abstract: Exclusive control using a semaphore mechanism of a specific computer is executed, and P and V operation instructions for the semaphore mechanism are issued according to a use request and use end information of a shared resource from another computer or the specific computer. Whether or not enabling information for the use request is informed to a use request source computer is determined according to the value of a semaphore variable. For this reason, even when a use of the shared resource is not enabled, enabling information is merely not sent back to another computer or the specific computer as the request source computer, and a lock server mechanism can be prevented from being set in an execution waiting state according to the unsuccessful P operation instruction.