Hewlett-packard Development Company, L.p.

Yu-Wei Wang

Kevin J Matherson

Robert E Sobol

John M Baron

Casey L Miller

Ren Wu

Zhehong Chen

Systems, methods, and other embodiments associated with producing spatially varying spectral response calibration data are described. One example method includes controlling a digital camera to capture characteristic data arrays from light sensors in the digital camera in response to the digital camera being exposed to light stimuli from a multi-spectral reference display. The data arrays will be acquired multiple times at multiple locations in multiple stimuli provided from the multi-spectral reference display. The method also includes controlling a calibration logic to manipulate characteristic data arrays to produce spatially varying spectral response calibration data as a function of using characteristic data arrays and known wavelengths of the light in light stimuli. The method may also include providing the spatially varying spectral response calibration data to a downstream consumer (e.g., correction process, quality control process), displaying the data, or storing the data.

Spatially-varying spectral response calibration data

In one implementation, an image sensor is calibrated by determining a spectral characterization for each image window of an image sensor, correlating the spectral characterization for each image window of the image sensor with a spectral property of a target illuminant, and generating a scale factor for each image window of the image sensor. The scale factor for each image window of the image sensor is generated based on the correlating.

Calibrating image sensors

A color constancy method and system include dividing an image into a plurality of sub-images and applying a plurality of color constancy algorithms to each of the sub-images. The outputs of each of the color constancy algorithms are analyzed for each of the sub-images to determine which of the color constancy algorithms give inconsistent results across the sub-images. The influence of the outputs of the algorithms providing inconsistent results is adjusted to decrease their influence (e.g. effect or weight) with respect to the outputs of algorithms providing consistent results. The outputs from the plurality of color constancy algorithms are combined based upon the adjustment of the outputs.

Color constancy method and system

A method is provided for correcting a captured image. The method comprises determining an illuminant for the captured image. When the determined illuminant matches a reference illuminant the image is corrected with a reference inversion mask. When the determined illuminant matches a first extreme illuminant, the reference inversion mask is modified using a first set of reference point ratios that corresponds to the first extreme illuminant and the image is corrected with the modified inversion mask. When the determined illuminant does not match the first extreme illuminant, a set of reference point ratios are calculated for the determined illuminant. The reference inversion mask is modified using the calculated set of reference point ratios and the image is corrected with the modified inversion mask.

Correcting a captured image in digital imaging devices

In a method of digital image compression, the spatial frequency content of a digital image is characterized using a relatively sparse sampling of data blocks from the image, and a quantization table is constructed based on the characterization of the spatial frequency content.

Image-adaptive quantization for JPEG compression

Consistent white balance between successive similar digital images of a scene is provided by comparing the digital images and, if they are sufficiently similar, maintaining substantially the same white balance setting in a second digital image as in a first digital image. The method is applicable to, for example, mixed-illuminant situations and may be implemented in both still-capture and video digital imaging devices.

Method and apparatus for maintaining consistent white balance in successive digital images

Methods for improving image quality of a digital image are disclosed herein.

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Fort Collins, CO, United States of America

Yu-Wei Wang