An image scanner is configured to: while changing a reading position by a position changer and sequentially emitting light of each of three colors in a turn-on sequence from a light source to a document, control a line sensor to read reflection light of emitted light, thereby acquiring gradation image data including gradation values of three colors for each pixel in one line; determine whether a top color shift occurs in the gradation image data at a determination position; in response to determining that the top color shift occurs at the determination position, replace gradation image data at the determination position with black image data; determine whether a bottom color shift occurs in the gradation image data at the determination position; and in response to determining that the bottom color shift occurs at the determination position, replace gradation image data at the determination position with white image data.

An image reading apparatus comprises a light source for repeatedly emitting first light having a first color, second light having a second color and third light having a third color toward a read target while moving the light source in a sub-scanning direction, first, second, and third sensors, each configured to sense a strength of first, second, and third reflected light, respectively, in a light reflected from the read target, and to output first, second, and third signal waveforms corresponding to the strength of the first, second, and third reflected light, respectively, and a controller. The controller is configured to execute a line-to-line correction for correcting a phase shift between the first, second, and third signal waveforms, and to correct a shift in a signal level caused by the line-to-line correction.

An image forming apparatus includes an image forming unit, a display, a reading unit configured to read a reference image formed on a test sheet by the image forming unit, wherein the reference image includes a mark corresponding to a reading order, a controller configured to control the image forming unit to form the reference image, cause the reading unit to execute a first reading operation, determine whether first read data is obtained, inform of a reading error if the first read data is not obtained in the first reading operation, cause the reading unit to execute a second reading operation, determine whether second read data is obtained, and inform of a reading error if the second read data is not obtained in the second reading operation, and an adjustment unit configured to adjust image forming positions based on the first read data and the second read data.

An image forming apparatus includes an image forming unit, a display, a reading unit configured to read a reference image formed on a test sheet by the image forming unit, wherein the reference image includes a mark corresponding to a reading order, a controller configured to control the image forming unit to form the reference image, cause the reading unit to execute a first reading operation, determine whether first read data is obtained, inform of a reading error if the first read data is not obtained in the first reading operation, cause the reading unit to execute a second reading operation, determine whether second read data is obtained, and inform of a reading error if the second read data is not obtained in the second reading operation, and an adjustment unit configured to adjust image forming positions based on the first read data and the second read data.

An image reading device that reads an image including a fluorescent color, including: a first light source having a maximum light emission intensity at a first wavelength; a second light source having a maximum light emission intensity at a second wavelength that is longer than the first wavelength; and an image reading chip configured to read the image. The image reading chip includes a pixel including a photodetector that performs photoelectric conversion on light received from the image, and the spectral sensitivity of the photodetector when photoelectric conversion is performed takes a maximum value at light having a wavelength in a region from 400 nm to 500 nm inclusive.

An image reading device that reads an image including a fluorescent color, including: a first light source having a maximum light emission intensity at a first wavelength; a second light source having a maximum light emission intensity at a second wavelength that is longer than the first wavelength; and an image reading chip configured to read the image. The image reading chip includes a pixel including a photodetector that performs photoelectric conversion on light received from the image, and the spectral sensitivity of the photodetector when photoelectric conversion is performed takes a maximum value at light having a wavelength in a region from 400 nm to 500 nm inclusive.

An image reading apparatus includes: a reader that reads an image formed on a print medium; and a backing part that is disposed at a position facing the reader and is capable of switching a color of a portion to be a background of the print medium upon reading by the reader to a plurality of colors according to a type of the print medium and/or a color read from the print medium.

An image processing apparatus processes image data to be used in a printing apparatus configured to perform forward and backward scan printing by using a print head in which nozzle arrays corresponding to multiple colors are aligned. The image processing apparatus includes: a setting unit configured to set a first control parameter in a case where image data to be processed does not include a line portion and to set a second control parameter in a case where the image data to be processed includes a line portion, the second parameter being different from the first control parameter; and a processing unit configured to perform, for the image data to be processed, processing to suppress a difference between a color printed in a forward scan and a color printed in a backward scan based on the control parameter set by the setting unit.

An image processing device performing color balancing of a first image and at least a second image is provided. The image processing device comprises a color balancing determination unit and a color balancing calculation unit. The color balancing determination unit determines a global gain vector (t) comprising at least two gain factors (.sup.n, .sup.n+1) of the first and second images by minimizing a cost function based upon reference pixel values of the first and second images. The first and second image reference pixels depict a shared color scene of the two images. The color balancing calculation unit performs color balancing of the first image based upon the gain factor (.sup.n) of the first image and to perform a color balancing of the second image based upon the gain factor (.sup.n+1) of the second image.

An image processing apparatus performs: acquiring target image data representing a target image including a plurality of pixels, the target image data including a plurality of sets of component image data representing respective ones of a plurality of component images; smoothing the plurality of component images to generate respective sets of a plurality of sets of smoothed component image data representing respective ones of a plurality of smoothed component images; enhancing an edge in each of the plurality of smoothed component images to generate corresponding one set of a plurality of sets of enhanced component image data; generating single-component image data including one type of component value corresponding to each of the plurality of pixels by using the plurality of sets of enhanced component image data; and specifying a plurality of edge pixels using the single-component image data, the plurality of edge pixels constituting an edge in the target image.