Provided is an operation method of an image signal processor (ISP) configured to perform signal processing on a raw image received from an image device, the operation method including generating a plurality of multi-scale images based on an input image, the plurality of multi-scale images having resolutions that are different from each other, iteratively performing a fast global weighted least squares (FGWLS) based operation on each of the plurality of multi-scale images to generate a final illuminance map, and outputting an enhanced image based on the final illuminance map and the input image.

An image processing portion of an image reading apparatus includes an extraction portion that extracts color information, a management portion that manages management color information that is an estimated value of the color information based on a control signal, a determination portion that determines whether or not the color information matches the management color information, and a writing control portion that causes the storage portion to store the pixel data when it is determined that the color information matches the management color information and that does not cause the storage portion to store the pixel data when it is determined that the color information does not match the management color information. When the color information does not match the management color information, the management portion adjusts the management color information to match the color information.

An apparatus includes, a change unit configured to change a pixel value of an edge pixel indicating an edge portion of an image based on the image data having the quantized color, wherein, in a case where the pixel value of the edge pixel is a pixel value changed by color reduction processing to decrease a luminance, the change unit changes the pixel value of the edge pixel to a pixel value of a pixel having a highest luminance among pixels surrounding the edge pixel, and wherein, in a case where the pixel value of the edge pixel is a pixel value changed by the color reduction processing to increase a luminance, the change unit changes the pixel value of the edge pixel to a pixel value of a pixel having a lowest luminance among pixels surrounding the edge pixel.

An apparatus includes, a change unit configured to change a pixel value of an edge pixel indicating an edge portion of an image based on the image data having the quantized color, wherein, in a case where the pixel value of the edge pixel is a pixel value changed by color reduction processing to decrease a luminance, the change unit changes the pixel value of the edge pixel to a pixel value of a pixel having a highest luminance among pixels surrounding the edge pixel, and wherein, in a case where the pixel value of the edge pixel is a pixel value changed by the color reduction processing to increase a luminance, the change unit changes the pixel value of the edge pixel to a pixel value of a pixel having a lowest luminance among pixels surrounding the edge pixel.

A method to reduce background noise in a document image includes: extracting, from the document image, a connected component corresponding to a background of the document image; generating a histogram of pixel values of the connected component; generating a replacement range using a range pruning algorithm that narrows a range of the histogram by iteratively discarding at least one pixel value and corresponding pixel count of the histogram from at least one side of the histogram; selecting, from the connected component, at least one pixel having a corresponding pixel value within the replacement range; converting the corresponding pixel value of the at least one pixel to a uniform background color; and outputting, subsequent to the converting, the document image.

A method to reduce background noise in a document image includes: extracting, from the document image, a connected component corresponding to a background of the document image; generating a histogram of pixel values of the connected component; generating a replacement range using a range pruning algorithm that narrows a range of the histogram by iteratively discarding at least one pixel value and corresponding pixel count of the histogram from at least one side of the histogram; selecting, from the connected component, at least one pixel having a corresponding pixel value within the replacement range; converting the corresponding pixel value of the at least one pixel to a uniform background color; and outputting, subsequent to the converting, the document image.

An image processing method is performed by an electronic device, the method including: obtaining, according to a quantity of pixels whose color feature values fall within color feature intervals in an original image, a first histogram corresponding to the original image; obtaining, according to a quantity of pixels whose color feature values fall within the color feature intervals in an upsampled image of the original image, a second histogram corresponding to the upsampled image; respectively determining, according to the first histogram and the second histogram, target color feature intervals matching the color feature intervals in the second histogram; and processing, according to the target color feature intervals matching the color feature intervals in the second histogram, the color feature values of the pixels falling within the color feature intervals in the upsampled image, to obtain a target image.

A system performs a method for processing an image of a machine-readable code. The method includes receiving an image of a machine-readable code comprising coded information, where the machine-readable code is at least partially obscured by a substance that has a predominant color; generating an adjusted image by adjusting a color space of the image based on the predominant color; binarizing at least a machine-readable code region of the image, wherein the machine-readable code region of the image depicts the machine-readable code; and decoding the binarized machine-readable code region to determine the coded information. Other apparatus and methods are also described.

Systems and methods are disclosed for image signal processing. For example, methods may include receiving an image from an image sensor, detecting, in a linear domain, color fringing areas in the image, correcting detected color fringing areas to obtain a corrected image, performing tone mapping to the corrected image to obtain a tone mapped image and storing, displaying, or transmitting an output image based on at least the tone mapped image.

An image processing apparatus sets, for at least one portion of a first image in which a brightness range is a first range, relationship information which associates an input brightness value with an output brightness value, changes, based on the relationship information, brightness values of pixels in the portion, and outputs a second image which has a second range of brightness. The relationship information is generated so as to associate, with each of the brightness values of the pixels in the portion, an output brightness value which does not exceed a value higher than the brightness value by a predetermined value, and to associate, with a brightness value which is not less than a feature amount among the brightness values of the pixels in the portion, a predetermined output brightness value falling within a predetermined range.