Provided is an image calibration method, an image formation device and a storage medium. The image calibration method includes: acquiring at least one of a first end color density value or a second end color density value of a calibration reference image along a direction to be calibrated; calculating a difference between the at least one of the first end color density value or the second end color density value and a target color density value, to obtain at least one of a first end color density difference value or a second end color density difference value; and performing uniformity calibration on an image to be calibrated if the at least one of the first end color density difference value or the second end color density difference value is greater than or equal to a preset difference threshold.

An image forming apparatus includes a converter configured to convert image data with use of a tone correction condition corresponding to a position in a main scanning direction of the image data, and an image forming unit, which includes a photosensitive member and an exposure portion configured to expose the photosensitive member to light based on the converted image data, and is configured to form an image on a recording medium. The image forming apparatus further includes a holding portion configured to hold a plurality of feedback conditions corresponding to a plurality of tones and a controller configured to control the image forming unit to form a plurality of test images, acquire measurement results for the plurality of test images, and generate the tone correction condition based on the measurement results and the plurality of feedback conditions.

An image processing apparatus is configured to: acquire a correction factor from a recording unit for recording, for each of a plurality of pixels, the correction factor for correcting a difference in pixel value corresponding to a difference between a spectral sensitivity and a preset reference spectral sensitivity in a predetermined wavelength range at a pixel of interest, based on image data generated by an image sensor, the image sensor having the plurality of pixels on which color filters of a plurality of colors with different spectral transmittances are respectively located, the color filters forming a predetermined array pattern; calculate a correction amount for correcting a pixel value of the pixel of interest based on the correction factor at the pixel of interest and pixel values of pixels surrounding the pixel of interest; and correct the pixel value of the pixel of interest by using the correction amount.

Certain examples described herein relate to the control of colorants and treatments for printing. In certain examples image data, a colorant color mapping and one or more treatment color mappings is obtained. The colorant color mapping may be used to map the image data to colorant application values. The one or more treatment color mappings may be used to map the image data to treatment application values. The colorant application values and treatment application values may be used to generate discrete print control instructions to apply the set of colorants and set of treatments to a printing substrate.

A system and method provide for automated evaluation of reference point pairs. For each of a set of reference point pairs in an input color space, a straight line connecting the reference points is sampled to generate a set of sampled points. Each of the set of sampled points in the input color space is converted to a sampled point in an output color space. For each of a set of color separations in the output color space, discontinuities are identified, based on the set of sampled points in the output color space. Candidate reference point pairs are identified in the set of reference point pairs for which at least one discontinuity is identified. The candidate reference point pairs can be validated by printing test sweeps, which are each derived from a respective set of sampled points in the output color space, and identifying contour artifacts in the printed test sweeps.

A test color sheet of color strips of color patches is used in calibration operations for a printing device. Control color patches are used to identify each color strip and the scanning direction of any measured data captured by a color measurement tool. The control color patches have a unique pattern for each row. The patterns are changed according to an updating process that associates each unique pattern with its respective color strip. Scanning operations may be done in any sequence or direction without having to update the data being captured. The control color patches include a specified control color that differs from the color patches used for calibration operations.

A test color sheet of color strips of color patches is used in calibration operations for a printing device. Control color patches are used to identify each color strip and the scanning direction of any measured data captured by a color measurement tool. The control color patches have a unique pattern for each row. The patterns are changed according to an updating process that associates each unique pattern with its respective color strip. Scanning operations may be done in any sequence or direction without having to update the data being captured. The control color patches include a specified control color that differs from the color patches used for calibration operations.

A liquid droplet ejecting apparatus comprises a liquid droplet ejecting head which has a nozzle array composed of a plurality of nozzles arranged in a first direction, a relative movement mechanism which relatively moves the liquid droplet ejecting head and a recording medium in the first direction, and a controller. The controller controls the liquid droplet ejecting head and the relative movement mechanism to record, on the recording medium, a nonuniformity correction pattern in order to correct any dispersion in a liquid droplet ejection amount among the plurality of nozzles. The controller is configured, in order to record the nonuniformity correction pattern, such that the liquid droplet ejecting head is allowed to eject liquid droplets from at least the first nozzle to thereby record a first pattern group, the relative movement mechanism is allowed to relatively move the liquid droplet ejecting head and the recording medium in the first direction by a predetermined distance, and the liquid droplet ejecting head is allowed to eject the liquid droplets from at least the second nozzle to thereby record a second pattern group.

A printing system is disclosed. The printing system includes at least one physical memory device to store halftone calibration logic and one or more processors coupled with the at least one physical memory device to execute the halftone calibration logic to receive print image measurement data corresponding to a first halftone design associated with each of a plurality of pel forming elements, generate measurement data for each of the pel forming elements based on the print image measurement data, generate a uniformity compensated halftone for each of the pel forming elements based on inverse transfer functions corresponding to each of the pel forming elements and the first halftone design and transmit the uniformity compensated halftone for each of the pel forming elements.

A printing system is disclosed. The printing system includes at least one physical memory device to store calibration logic and one or more processors coupled with the at least one physical memory device to execute the calibration logic to perform uniformity compensation, including receiving print image measurement data corresponding to primary color markings and secondary color markings printed by pel forming elements, wherein each of the pel forming elements is associated with one of a plurality of primary colors, generating a first set of transfer functions based on the print image measurement data, wherein the first set of transfer functions includes a transfer function for each of the pel forming elements associated with a primary color, generating a second set of transfer functions based on the print image measurement data, wherein the second set of transfer functions includes transfer functions for each of the pel forming elements associated with a plurality of secondary colors, generating a set of inverse transfer functions for each of the pel forming elements based on the first set of transfer functions and the corresponding second set of transfer functions and generating a uniformity compensated halftone design based on the set of inverse transfer functions and a first halftone design.