An image processing apparatus includes a processing unit that shifts plural pieces of pixel data so as to suppress deviation in a sub-scanning direction at the time of image formation; a storage unit that stores the plural pieces of pixel data; and a converting unit that converts addresses of the plural pieces of pixel data such that a predetermined number of pieces of pixel data which are a unit of processing of the shift process are stored in a cache memory used by the storage unit at once.

An image reading apparatus includes an imaging device to image a medium, and a processor to detect a plurality of edge pixels in a sub-scanning direction based on gradation values of a plurality of pixels of which positions in a main scanning direction are mutually the same and a distance between pixels in the sub-scanning direction is within a predetermined range in an input image acquired by imaging the medium by the imaging device, detect an end portion in the main scanning direction of a front end or a rear end of the medium based on a positional relationship between the detected plurality of edge pixels in the sub-scanning direction, and output information relating to the detected end portion.

An outer peripheral member disposed at an outer periphery of a platen glass includes first and second reference surfaces. The first reference surface is a lower surface of an area extending along a side edge portion of the platen glass at an end in a main scanning direction. The second reference surface is located adjacent to the first reference surface in a second direction and differs in light reflectance from the first reference surface. An image processing portion determines whether outer periphery pixel data of an outer periphery area in line image data acquired successively while a scanning unit is moving, satisfies a border condition. A unit driving portion positions the scanning unit to a home position by moving the scanning unit a predetermined distance from where the scanning unit is located when it is determined that the outer periphery pixel data satisfies the border condition, and stops it.

An image forming apparatus includes a lens, first and second light sensors, a change amount detector, and a controller. The lens is in one of laser scanning systems. The first light sensor is in the one of the laser scanning systems at a position such that the scanning beam is incident on a detection surface thereof. The second light sensor is adjacent to the first light sensor and angled with respect to the first light sensor. The second light sensor is arranged such that the scanning beam is also incident on a detection surface thereof. The change amount detector is configured to detect a time interval of scanning of the first and second light sensors by the scanning beam. The controller is configured to perform an operation to calibrate the laser scanning systems when the time interval is equal to or greater than a first threshold value.

A medium conveying apparatus includes a conveyance roller to convey a medium, a DC motor to drive the conveyance roller, a processor to rotate the DC motor, an encoder to output a first pulse signal whose cycle varies according to a rotation speed of the DC motor, and an imaging device to acquire an image acquired by imaging a conveyed medium in response to a pulse of a second pulse signal whose cycle is constant. The processor detects a number of pulses of the second pulse signal included in a predetermined cycle of the first pulse signal, and discards images acquired by the imaging device in the same number of pulses as difference between the detected number of pulses and a reference number, in a next cycle of the predetermined cycle of the first pulse signal, when the detected number of pulses exceeds the reference number.

In an image processing system, an image reading apparatus determines whether an error occurs on a read image that is an image read by an image sensor, and generates and transmits data including the read image and error information that is information indicating presence or absence of occurrence of the error, and an image processing apparatus receives the data and performs, on the read image, image processing corresponding to the presence or absence of occurrence of the error, based on the error information.

An image generation control unit generates a connection image indicating a plurality of print target images. The connection image is an image for being printed using a first region for being used in the n-th printing processing and a second region for being used in the (n+1)-th printing processing. An image processing unit generates a first image for being printed using the first region and a second image for being printed using the second region.

An image reading apparatus includes: a reading unit, which is configured to read an original placed on an original table in a main scanning direction by irradiating the original with light; and a sub-scanning size detector, which is configured to detect presence or absence of the original on the original table by radiating invisible rays. When the platen cover forms an angle of equal to or smaller than a first angle with respect to the original table, the image reading apparatus determines a size of the original in a sub-scanning direction in accordance with a detection result acquired from the sub-scanning size detector. When the platen cover forms an angle equal to or smaller than a second angle, which is smaller than the first angle, with respect to the original table, the image reading apparatus determines a size of the original in the main scanning direction.

A reading device includes a position reference member and a reader. The position reference member has a reference pattern that includes a line extending in a prescribed direction. The position reference member is configured to relatively move in a direction orthogonal to the prescribed direction. The reader includes a plurality of sensor chips, each of the sensor chips including a plurality of pixels. The reference pattern corresponds to each of the sensor chips of the reader.

An image forming apparatus includes a rotating body to form an image, a sensor to detect a home position of the rotating body, a processor to acquire image density data of the image formed by the rotating body in odd-numbered rotation and even-numbered rotation of the rotating body separately based on a rotation home position signal output by the sensor, extract an image density fluctuation caused by a rotation of the rotating body, and correct an image forming condition based on the image density fluctuation.