An image reading apparatus includes an imaging device for generating a white reference image of a white reference member and a document image of a document and a periphery of the document, and a processor for performing first processing for detecting a dirt substance from the white reference image, generating data for shading correction based on the white reference image, correcting the document image using the data for shading correction to generate a correction image, and performing second processing for detecting a dirt substance from the correction image. One of the first processing or the second processing is performed using a dirt substance detection result of the other one of the first processing or the second processing.

An image reading apparatus according to an embodiment includes an image reading unit configured to generate reference data by reading a reference surface and to generate image data by reading a sheet. A reference unit has a reference surface. A shading correction unit determines whether a portion of the reference surface includes a contaminant based on image data generated by the image reading unit reading the portion of the reference unit. When the portion of the reference surface is determined to not include a contaminant, the shading correction unit generates reference data based on the image data generated by the image reading unit reading the portion of the reference surface determined to not include a contaminant.

A background image is acquired by imaging an opening plate as a background of an original document in a state where the original document is not arranged. Next, an original document including background image is acquired by imaging the same range as the background image in a state where the original document is arranged on an upper surface of the opening plate. Next, a difference image is generated by subtracting the background image from the original document including background image. In addition, an inverse difference image is generated by subtracting the original document including background image from the background image. A region of the original document is detected based on the difference image and the inverse difference image.

An image processing apparatus includes a receiver and a correcting unit. The receiver receives a first read value and a second read value. The first read value indicates a result of reading a first color by a reader from a recording medium in which the first color is applied to a first area in which in-plane density unevenness is confirmable within the recording medium. The second read value indicates a result of reading a second color by the reader. The second color is different from the first color and is applied to a second area that is substantially the same as the first area in a superimposed manner. The correcting unit corrects in-plane density unevenness of the second color applied to the first color in the superimposed manner based on the first read value received by the receiver and the second read value received by the receiver.

The inventive plastic card permits a scuba diver to photograph underwater such as at 100 feet, without using external lighting, and to achieve quality photographic images as if external lighting actually had been used during the underwater photography.

A scanner includes an image read unit including a linear image sensor having a length in a main scanning direction, a compensation value calculation unit to compare data read from a main scanning reference pattern including a plurality of main scanning sections arranged in the main scanning direction with data of the main scanning reference pattern that is previously stored, and to calculate a plurality of main scanning scale compensation values respectively corresponding to the plurality of main scanning sections, and an image processing unit to compensate for distortion in the main scanning direction by dividing an image read from the document into a plurality of main scanning image areas respectively corresponding to the plurality of main scanning sections and applying the plurality of main scanning scale compensation values respectively to the plurality of main scanning image areas.

A document reading apparatus including: a detector configured to detect presence of a document on a document tray; a conveyance unit configured to convey the document; a reading unit configured to read the document conveyed by the conveyance unit at a first position; and a reference member. When the detector detects the presence of a document, the reading unit reads the reference member to determine a shading correction value while being moved from a second position to a third position located between the first position and the second position. When the shading correction value is to be determined again in a period from when the shading correction value is determined until when a receiver receives an instruction to start reading, the reading unit reads the reference member while being moved from the second position toward the first position after having been moved from the third position to the second position.

A document reading apparatus including: a detector configured to detect presence of a document on a document tray; a conveyance unit configured to convey the document; a reading unit configured to read the document conveyed by the conveyance unit at a first position; and a reference member. When the detector detects the presence of a document, the reading unit reads the reference member to determine a shading correction value while being moved from a second position to a third position located between the first position and the second position. When the shading correction value is to be determined again in a period from when the shading correction value is determined until when a receiver receives an instruction to start reading, the reading unit reads the reference member while being moved from the second position toward the first position after having been moved from the third position to the second position.

In an example, two images of a printed calibration image are acquired using two measurement devices. The measurement devices are offset along an axis so that the two images correspond to two portions of the printed calibration image overlapping along the axis. The printed calibration image comprises a pattern extending across the printed calibration image in the direction of the axis, the pattern defining a shape so that in each image, a portion of the pattern appears as different from a straight line parallel to the axis. The two images are aligned using the two portions of pattern.

The image reading apparatus includes a reading unit, a reading region in which a first region in which a member that suppresses entry of external light is disposed and a second region other than the first region are arranged in a main scanning direction of the reading unit, and a controller, wherein the controller calculates intensity of external light in the second region based on a reading value in the reading region, wherein the reading value is obtained by the reading unit, determines whether the intensity of the external light exceeds a threshold value, performs a first shading correction on a reading value of a document transported to the reading region when the intensity of the external light exceeds the threshold value, and performs a second shading correction on the reading value of the document when the intensity of the external light does not exceed the threshold value.