An image reading apparatus according to an embodiment includes an image reading unit that generates reference data by reading a reference surface and generates image data by reading a sheet. A reference plate includes the reference surface for generating the reference data for shading correction of the image reading unit and a background surface for background of a sheet to be read to generate the image data. A control unit controls the positions of the image reading unit and the reference plate to be at a first position relative to each other when the reference data is to be generated and at a second position relative to each other when the image data is to be generated. The second position is different from the first position. A shading correction unit performs the shading correction in the image reading unit based on the generated reference data.

An image capturing apparatus comprises an image sensor in which pixels including a correction pixel region and an effective pixel region are arrayed two-dimensionally; and a creating unit configured to create uncompressed or losslessly-compressed image data from signals acquired from the effective pixel region and the correction pixel region, wherein in the case where a resizing process is to be carried out on the effective pixel region included in the image data, the creating unit does not carry out the resizing process on the correction pixel region.

An image reading device includes: a scanner having characteristics of causing a distorted sine wave being formed by its obtained image data and being represented as an array of shade values arranged in a main scanning direction; a reference member to be scanned; a hardware processor that: obtains a shade value at each main scanning coordinate from shading reference data obtained from the reference member; detects the start and end position of a distorted waveform range in the shading reference data; defines the start and end position of a target range as the main scanning coordinates of two peaks, the two peaks being in a distorted sine wave formed by the shading reference data, the two peaks being within a predetermined reference distance to the right and left of the start and end position; and replaces a part of data in the target range with a substitute part of data.

In one embodiment, a stated reflectance identifier for a media to be printed on during fulfillment of a print job is received. Utilizing an optical sensor and an illuminator, a measurement is taken of light from the illuminator reflected off the media. The measurement is compared to a stored average brightness value. Responsive to determining the measurement is within a range of the average value, the average value is adjusted to include the measurement, and printing on the media is caused according to the job. Responsive to determining the measurement is outside the range, the measurement is compared to a database associating brightness measurements and reflectance identifiers to determine an estimated reflectance identifier for the media. The estimated identifier is sent to a user and the user is prompted to perform a correction event. The media is printed on according to the job.

An image reading device includes: a sensor module having a light source and a plurality of sensors; a white reference plate; and an image processor that generates correction data to be used for shading correction and performs the shading correction on image signals, using the correction data. The light source is configured to switch between at least a first luminous intensity and a second luminous intensity lower than the first luminous intensity. The image processor acquires intermediate data by causing the plurality of sensors to acquire an image signal of the white reference plate illuminated with the second luminous intensity, generates black correction data, based on the intermediate data, and performs the shading correction, using the black correction data, so that a density unevenness, in an image, caused by interference between image signals from the plurality of sensors.

A document reading apparatus includes a calculation unit configured to calculate first shading data of a first sensor based on first measurement data acquired by the first sensor by reading a first reference member and calculate second shading data based on second measurement data acquired by a second reading sensor by reading a second reference member and profile data, and a verification unit configured to verify the profile data, and if the profile data is judged incorrect as a result of the verification, the calculation unit calculates the second shading data from the second measurement data acquired by the second reading sensor by reading the second reference member without using the profile data, and if the profile data is judged correct as a result of the verification, the calculation unit calculates the second shading data based on the second reference data and the profile data.

A shading correction device includes a reference acquirer that acquires a reference pixel value W in a captured image of a color measurement reference object, a target pixel value acquirer that acquires a pixel value S in a captured image of a measurement target, a bit shift value acquirer that acquires a bit shift value k2 based on the reference pixel value W, a lookup table storing a variable G.sub.2 (=2.sup.k1/W>>k2) corresponding to W>>k2, and a calculator that reads the variable G.sub.2 corresponding to the reference pixel value W and the bit shift value k2 from the lookup table and calculates a shading correction value R.sub.dec of each pixel in the captured image of the measurement target using Expression (5):

[00001]$\begin{array}{cc}{R}_{\mathrm{dec}}=\left(F.Math.G_2\right)\left(k.Math..Math.1+k.Math..Math.2\right)+B.Math..Math.\mathrm{where}.Math..Math.F=S.Math.\left(A-B\right)+\left\{W1\right\},G_2=\frac{2^{k.Math..Math.1}}{Wk.Math..Math.2},& \left(5\right)\end{array}$

and A, B and k1 are integer constants.

A scanner includes a transport mechanism that continuously transports a plurality of documents, a sensor, a control unit that performs correction of a read image which the sensor reads by using a correction value, a calculation unit that calculates the correction value based on a result from which the sensor reads a reference region between the documents, and a storage unit that sequentially stores the correction value in any of a plurality of storage regions, in which the control unit switches the storage region where the correction value used for the correction is read out to the storage region where the calculated correction value is stored, if storing of the calculated correction value is completed.

A printer includes a discharge unit, a first printing unit disposed along a sheet conveying path extending from the discharge unit and configured to print an image on a first sheet while the first sheet is conveyed from the discharge unit to the first printing unit and then to the discharge unit, a second printing unit disposed farther from the discharge unit than the first printing unit along the sheet conveyance path and configured to print an image on a second sheet while the second sheet is conveyed towards the discharge unit therethrough, a scanning unit disposed along the sheet conveying path between the discharge unit and the first printing unit, and configured to scan a surface of the first sheet, and a control unit configured to perform a shading correction of the scanning unit using the second sheet as a white reference.

In an image reader, a controller acquires a set of first black data for each pixel in a line by reading one line worth of image via a light receiver with a light source being turned off when a detector detects that a cover is in an open state. Subsequently, the controller acquires a set of white data for the each pixel in the line by reading a white reference member via the light receiver with the light source emitting light when the detector detects that the cover is in the open state. The controller calculates a set of correction data for the each pixel in the line by subtracting the set of first black data of the each pixel from the set of first white data of the each pixel. The set of correction data is used in a shading correction.