In an image data conversion device, color image data is represented in gray scale, a histogram of brightness values is created for the gray-scaled image data, it is determined based on the created histogram which image pattern of a plurality of image patterns the gray-scaled image data is classified into, a range subjected to gamma correction and a range fixed to at least one of a minimum value and a maximum value of gray scale are set for each image pattern, and image data conversion including the gamma correction is performed on the gray-scaled image data.

An image processing apparatus of an embodiment includes an image processing unit to convert a color image to a monochrome image. The color image comprises pixels with a plurality of color components. The image processing unit is configured to generate a histogram from the monochrome image showing a color intensity gradation in the monochrome image by pixel frequency. A processor is configured to obtain a first threshold value based on the histogram, determine for each color component of each pixel in the color image whether or not each color component of the pixel is light based on the first threshold value, and generate a corrected color image by removing a background coloring from the color image by correcting each pixel for which all the color components are determined to be light.

A method to reduce background noise in a document image. The method 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, using a non-linear mapping function based on the histogram, a non-linear probability distribution of the pixel values in the connected component, generating, based at least on a comparison between the non-linear probability distribution and a predetermined threshold, a replacement range of the pixel values, selecting, from the connected component, a pixel having a pixel value within the replacement range, and converting the pixel value of the pixel to a uniform background color.

An image processing apparatus includes a filtering processing unit that executes a filtering process to suppress background noise of input image data; a threshold setting unit that sets a binarization threshold for the input image data; a background noise determination threshold setting unit that determines that a tone value at which the number of pixels of background noise of the input image data reaches a peak is a background peak tone value and that sets, as a background noise determination threshold, a tone value having a density higher than a density of the background peak tone value and having a number of pixels within a specific range of percentages, of the number of pixels at the peak; a background noise reduction processing unit that executes a background noise reduction process on the input image data and a binarization processing unit that executes a binarization process on the input image data.

An image processing apparatus of an embodiment includes an image processing unit to convert a color image to a monochrome image. The color image comprises pixels with a plurality of color components. The image processing unit is configured to generate a histogram from the monochrome image showing a color intensity gradation in the monochrome image by pixel frequency. A processor is configured to obtain a first threshold value based on the histogram, determine for each color component of each pixel in the color image whether or not each color component of the pixel is light based on the first threshold value, and generate a corrected color image by removing a background coloring from the color image by correcting each pixel for which all the color components are determined to be light.

An image forming apparatus includes an image forming portion, a first acquisition processing portion, a second acquisition processing portion, and an adjustment processing portion. The image forming portion forms an image on a sheet. The first acquisition processing portion acquires a captured image of the sheet. The second acquisition processing portion acquires a specific value that indicates a difference between a gradation value of a pixel that, among pixels included in the captured image acquired by the first acquisition processing portion, corresponds to a higher part of an outer surface of the sheet, and a gradation value of a pixel that, among the pixels included in the captured image, corresponds to a lower part that is lower than the higher part. The adjustment processing portion adjusts an image forming condition of the image forming portion based on the specific value acquired by the second acquisition processing portion.

An image processing apparatus is provided with a converter to convert a first color image into lightness information and color information other than the lightness information, a lightness compressor to generate compressed lightness information obtained by decimating a pixel value from the lightness information, a reconverter to combine the compressed lightness information and the color information to generate a second color image, an edge extractor to extract an edge included in the first color image, and a pixel value changer to change a pixel value at a position of the edge in the second color image while maintaining similar colors, to generate a third color image.

A system accesses an image with each pixel of the image having luminance values each representative of a color component of the pixel. The system generates a first histogram for aggregate luminance values of the image, and accesses a target histogram for the image representative of a desired global image contrast. The system computes a transfer function based on the first histogram and the target histogram such that when the transfer function is applied, a histogram of the modified aggregate luminance values is within a threshold similarity of the target histogram. The system modifies the image by applying the transfer function to the luminance values of the image to produce a tone mapped image, and outputs the modified image.

An image processing apparatus includes a filtering processing unit that executes a filtering process to suppress background noise of input image data; a threshold setting unit that sets a binarization threshold for the input image data; a background noise determination threshold setting unit that determines that a tone value at which the number of pixels of background noise of the input image data reaches a peak is a background peak tone value and that sets, as a background noise determination threshold, a tone value having a density higher than a density of the background peak tone value and having a number of pixels within a specific range of percentages, of the number of pixels at the peak; a background noise reduction processing unit that executes a background noise reduction process on the input image data and a binarization processing unit that executes a binarization process on the input image data.

Embodiments of the present invention disclose a method, computer program product, and system for cataloging images based on a gridded color histogram analysis. The computer accesses an image gallery specified by a user, wherein the image gallery is at least one of an image gallery stored on a user computing device, an image gallery stored on a user account at a third-party image storage, or an image gallery searched on the web. The computer receives a request to search the image gallery specified by the user. The computer performs a search of the image gallery, wherein the search is using a color based histogram algorithm based on a user input. The computer transmits a cataloged and sorted image gallery to the user computing device to be displayed.