Abstract: An adaptive image tone mapping curve based on perceptual preference guidelines is generated as a sigmoidal function, in which the sigmoidal function parameters (slope and shift) are determined by original image statistics. Tone curves generated for different images each have a smooth sigmoidal shape, so that the tone mapping process does not change the image histogram shape drastically.

Abstract: A streamlined technique for obtaining interpolated color output values from corresponding color input values based on color output values stored in a color look-up table, with tetrahedral interpolation being applied so as to dissect each cubic grid of the color look-up table into plural tetrahedrons. According to the invention, processing efficiency is increased by avoiding the use of conditional branches when making a determination as to which of the plural dissected tetrahedrons a particular color input value falls. Preferably, rather than making such a determination, weights for all possible tetrahedrons for one cube are stored in a temporary look-up table, and an index into the temporary look-up table is calculated based on the magnitude of component values for each color input value. The index is calculated in a block of code that does not include conditional branches that are conditioned on the relative magnitude of the component values of the color input value.

Abstract: A circuit for developing correction signals for on-line controlling a precorrection arrangement in an HDTV 8VSB digital signal transmitter. The transmitted signal is sampled, sorted, smoothed and sliced to determine the symbol amplitude levels of the transmitted multilevel symbols. The centers of the sliced clusters of sampled symbol levels are used to determine the symbol amplitude levels. Correction signals for compensating the precorrection arrangement are developed based upon the determined symbol levels and the known symbol levels.

Abstract: A printer is interrogated with regard to a plurality of processing functions thereof and, in response to the interrogation, response information is sent from the printer. An image object delivered from an application program is analyzed and, on the basis of the analytical results and the response information from the printer, it is determined whether the number of color elements and number of palettes of the image object are capable of being supported by the printer. If they are capable of being supported, control information for output to the printer is created based upon the image object. If the number of color elements and number of palettes are incapable of being supported by the printer, then control information for output to the printer is created from the original image object upon taking into consideration the functions possessed by the printer.

Abstract: A smoothing circuit smoothes lookup tables generated by a color conversion table generator, using a filter function selected from a filter function storage circuit, and supplies smoothed lookup tables to a color processing circuit. Density data supplied from a calibration circuit are converted into halftone dot % data according to the smoothed lookup tables. The halftone dot % data are interpolated and then converted into LD control data, which are supplied to laser diodes.

Abstract: Methods and apparatus that generate data structures representing the frequency with which colors occur in a collection of colors, such as occurs in a raster image. The invention provides a list consisting essentially of first generation entries and combines first generation entries to form a list consisting essentially of second generation entries. Each first generation entry has an associated color set of one or more colors. Each first generation entry represents the frequency with which colors in the associated color set appear in the image. The color sets for all of the first generation entries are mutually non-intersecting. Particular embodiments have the following features. Each second generation color set corresponds to a volume of the color space. All second generation color sets have the same size. The second generation entries can be combined to form a list of third generation entries.

Abstract: Palletized image enhancement systems and methods enhance palletized images by &sgr;-filtering the palletized image. Palletized images, such as GIF images, are analyzed to obtain a number of &sgr; filter parameters based on the global image features of the palletized image. Local portions of the image data are analyzed to determine which of the &sgr; filter parameters should be used for each particular portion. The &sgr; filter parameters are determined based on histograms of the color palette of the palletized image data. As a result, a good balance between color re-creation and image sharpness in the enhanced palletized image is obtained.

Abstract: Data in only three colors is printed in the three colors plus black. The coverage amount represented by the smallest intensity of the three colors is determined. When that amount is above a predetermined value at which observable grain becomes minimal, an exponent value is determined and a formula is followed. As an additional improvement, lightness is redefined on a model which favors less black at the lighter values and more black at the darker values. Hue is to remain the same, and is known from the original color data. The chroma is refined based on the original chroma, CMY and CMYK full gamut boundaries. Since black, lightness, chroma and hue are known, the new three color values are found by known techniques.

Abstract: A method for calibrating a printer includes printing a first set of color samples with the printer, reflecting at least a portion of the printer gamut. Each printed color sample in the set of samples is measured calorimetrically, to determine the printer's response thereto. The colorimetric response is compared with a predictive model of printer behavior for that portion of the printer gamut. In a portion of the printer gamut wherein the calorimetric response differs from predicted printer behavior, the printer generates a new set of color samples, for printing. The new set of color samples is secondarily measured to determine the printer's colorimetric response thereto; and using the initial measurements and the secondary measurements, a color calibration table is generated for use by the printer in converting device independent colors to device dependent colors.

Abstract: Digital images often have undesired color casts due to unusual illuminant sources. A color correction method is provided that uses adaptive segmentation to identify the presence of such casts, estimate their chromatic strength, and alter the image's near-neutral-color regions to compensate for the cast. The method identifies most major objects in a scene and their average color. A color space having an achromatic axis is provided with a default gray radius that is used for establishing bins of neutral color in a chromatic plane. The bins are populated with the pixels of the digital color image based on pixel chromaticity. A color histogram computed with chromaticity peaks for the pixels in the bins within the default gray radius. The default gray radius is adjusted to a gray radius based on the chromaticity peaks in the color histogram.

Abstract: An image processor includes an input device that inputs image data representing a target image, and a color gamut mapping device that performs a color gamut mapping process. The image processor also includes a color reproduction process device that performs a color reproduction process, and a judgment device that judges whether a monochromatic mode for forming an image on a recording medium is set. A controller controls the color gamut mapping device and the color reproduction device, with the controller inhibiting the color gamut mapping device from performing a color mapping process on the input image data when a judgment is made that the monochromatic color mode is set.

Abstract: Provided is a system for eliminating background noise, i.e. unwanted dots of ink in the background of a document which is to be reproduced by a copier. An STS module collects statistics on a stream of pixels representing an original document generated by a scanner of the copier. The statistics are used by an MIC module to determine a reference background color value of the scanned document. The reference background color value and pixel values of pixels included in the pixel stream are compared by an RTE module and the results of comparison are used to adjust, when necessary, the pixel values remove the undesirable background noise.

Abstract: A printer is interrogated with regard to a plurality of processing functions thereof and, in response to the interrogation, response information is sent from the printer. An image object delivered from an application program is analyzed and, on the basis of the analytical results and the response information from the printer, it is determined whether the number of color elements and number of palettes of the image object are capable of being supported by the printer. If they are capable of being supported, control information for output to the printer is created based upon the image object. If the number of color elements and number of palettes are incapable of being supported by the printer, then control information for output to the printer is created from the original image object upon taking into consideration the functions possessed by the printer.

Abstract: The present invention includes a digital image reading apparatus and method which can determine the characteristic value of film with pinpoint accuracy and can properly determine the image processing conditions for each frame using the characteristic value even if the images recorded on the film have color failure.

Abstract: A method for extracting a histogram and a cumulative distribution function (CDF) value for an image enhancement apparatus, and a circuit therefor are provided. The histogram extraction is performed during an active section of a video signal. The level of an input digital video signal is input as an address of a memory, and a data value stored at the address is increased. The processes are repeated during a one-screen period, thereby obtaining a histogram value indicating the number of samples distributed to each gray level. Also, a CDF value of each gray level is obtained by cumulatively integrating the number of samples from the lowest gray level on the basis of the histogram value obtained, during a vertical blanking period of the video signal. Therefore, the histogram/CDF extracting circuit can be built of simple hardware and an integrated structure, even though it performs both histogram and CDF extractions.

Abstract: In a digital full color image processor, color data are obtained by reading a color image with a color image sensor. An image forming mode of the color image such as background level and magnification is specified, and the image forming mode is changed according to the specified image forming mode when the color data is processed. A reference value for area discrimination is changed according to the image forming mode. Then, an area such as a black portion or a dot area in the color data is discriminated for image processing of the color data with the reference value, and the color data is processed according to the area discrimination.

Abstract: A non-linear response correction apparatus and method reduce look up table size and output error. In one embodiment, a range of an N-bit input signal is split into two or more sectors, based on a gradient of a non-linear correction curve and an allowable error, and then a N-bit input signal is divided into U upper bits and D lower bits where U and D depend on which sector contains the input signal. First and second look up tables read first and second data stored therein, respectively, using the upper bits of the digital signal as an address. The first data is the difference between a corrected signal and the input signal, and the second data is the gradient of the corrected signal with respect to the gradient of the input signal. The second data read from the second look up table is multiplied by the lower bits, and the first data read from the first look up table is added to the upper bits.

Abstract: Luminance levels of an analog or digital image signal entered from outside are detected as a luminance histogram. Based on the luminance histogram, a black luminance level and a white luminance level are determined, and are assigned respectively to a darkest tonal level and a lightest tonal level of a gradation range available for printing. To those pixels having luminance levels between the black and white levels, tonal levels between the darkest and lightest tonal levels are assigned according to a gradation conversion curve. The gradation conversion curve is selected among from a plurality of predetermined conversion curves depending upon a scene discrimination coefficient. The scene discrimination coefficient is calculated by multiplying the frequency of each luminance level shown in the luminance histogram with a different luminance coefficient predetermined according to the luminance level, and accumulating multiplication results of all the luminance levels.

Abstract: A color conversion device includes a region judging section for judging which region of a three-dimensional color space contains an input value, and/or a representative points-dispersed axis selecting section for selecting a representative points-dispersed axis which is nearest to said input value. Additionally, the color conversion device includes a representative points selecting section for selecting representative points in the vicinity of the input value among representative points discretely arranged along (or within) the selected representative points dispersed axis; a look-up table (LUT) which stores coordinates of representative points and color correction data; and a linear interpolation section for performing color conversion by weighting based on the selected representative points.

Abstract: In a digital full color copying machine, image signals of red, green and blue are converted to a value signal, and histograms of the value signal for chromatic dots and achromatic dots respectively are generated. Then, a document type, such as a color standard document, a color photograph document, a color standard document having a colored background, a black-and-white standard document, or a black-and-white photograph document, is determined automatically based on the histograms. Background level of a copy is controlled automatically at an appropriate level both for a color document and for a black-and-white document having a white background according to the document type by gradation correction of the value signal. Thus, background processing is performed irrespective of a color document or a black-and-white document.

Abstract: A face (skin color) area of a person is extracted with minimized error irrespective of different skin colors of the human races. A hue value calculating portion determines a hue value from an input image (RGB signal). A primary discriminating portion extracts pixels having hue value that lies in a specified range defined by limiting values outputted from a control portion. A pixel-counting portion counts the extracted pixels. The control portion selects a threshold value for extracting a face area according to the count of the extracted pixels and outputs the threshold value to a face-area extracting portion which in turn extracts a face area according to the threshold value.

Abstract: An image processing apparatus includes a feature data extracting circuit for detecting feature data indicative of density characteristics of a document based on image signals inputted from an input terminal, a density correction table selecting circuit composed of a neural circuit network which is learned beforehand so as to recognize image characteristics based on the feature data, and a density correcting circuit for selecting a density correction table in accordance with image characteristics based on a selection signal from the density correction table selecting circuit so that the density of image signals is corrected based on the density correction table. As a result, characteristics of the document are extracted, so that the density of the image signals can be corrected based thereon.

Abstract: A color-image reader reads a recorded color image from a recording medium, and has an image sensor for sensing the color image as at least a first and second regular series of monochromatic image signals during a regular reading operation. A first optimal exposure period is determined regarding the first regular series of image signals, and a second optimal exposure period is determined regarding the second regular series of image signals. A first set of color-correction parameters is determined based on a first provisional series of image signals, sensed from the color image by the image sensor over the first optimal exposure period. A second set of color-correction parameters is determined based on a second provisional series of image signals, sensed from the color image by the image sensor over the second optimal exposure period. A color balance is performed among the first and second regular series of image signals by using the first and second sets of color-correction parameters.

Abstract: Image processing parameters for gradation correction of a digital image from a scene, which includes specular reflections may be seriously influenced by the presence of those specular reflections. Therefore, a method is developed to detect the presence of specular reflections in a scene, to modify the exposure time of the photo-sensitive means, which converts a luminous image to electronic image signals and to apply a gradation correction to the image data thus acquired. In one embodiment a digital camera is used to capture the image data, a cumulative histogram is built and two characteristic cumulative frequencies are used to determine via the histogram specular densities and highlight densities. The relative position of these density values indicates whether specular reflections are present, and give suitable parameters for setting an optimal exposure time and for computing a gradation correction curve.

Abstract: An input image is divided into relatively small blocks of pixels. Border data defining the areas are periodically calculated. For each pixel, a pair of selection pulses indicative of the area where the pixel is located is generated. In response to the pair of pulses, the gray scale characteristic is calculated for each area. The gray scale of the input image is corrected using one of the gray scale characteristic associated with each area to providing a corrected image signal for the area. In response to the pair of pulses, the corrected image signals are combined into an output image signal. An optimal gray scale correction is made for each area. The selection pulses are configured to gradually change near the borders thereby making the reproduced image appear natural.

Abstract: A fully regularized printer LUT with improved accuracy is generated by measurement of color patches at a first LUT interval and measurement of color patches for critical color regions at intermediate points between the first LUT interval. Thereafter, a fully regularized LUT is produced at a second LUT interval which is less than the first interval, by insertion of all measurement values into the regularized LUT and by insertion of interpolated values into the regularized LUT at grid points that were not actually measured. In a case where eccentric points have been measured, meaning points that are closely adjacent to the regularized LUT grid, actually-measured values are not entered into the LUT grid; rather interpolated values are entered, with interpolation being such that post-processing of the entries yields the measured value for the eccentric point.

Abstract: An image reader has an image sensor for sensing an image, as a series of pixel signals, by exposing the sensor to light rays. The sensor exhibits a characteristic curve, having at least a partial linear section, describing a relationship between a level-value of a pixel signal and an exposure period over which the sensor is exposed to the light rays. First and second effective maximum level-values are determined from first and second series of pixel signals, obtained by exposing the sensor to the light rays, over first and second exposure periods, respectively. The second exposure period is longer than the first exposure period. The exposure periods are encompassed within the partial linear section of the characteristic curve, and an optimal exposure period of the image is determined based on the first and second effective maximum level-values corresponding to the first and second exposure periods, and an effective maximum level-value corresponding to the optimal exposure period.

Abstract: A technique for calibrating a scanner wherein once the scanner is calibrated, the scanner's device-dependent tristimulus values (e.g., RGB) for an arbitrary color are transformed to a device-independent representation (e.g., XYZ) of the arbitrary color in a computationally efficient manner. The scanner is characterized in a manner that a corrected device-independent representation of an arbitrary scanned color can be determined on the basis of a pair of chromaticity coordinates in a chromaticity space having (i) a pair of chromaticity coordinates that span hue and chroma (saturation), and (ii) a lightness coordinate that is a luminance correlate (monotonic function of luminance). A look-up table stores XYZ values and a lightness value. A set of XYZ values and a lightness value are retrieved from the table as addressed by a pair of chromaticity values corresponding to the scanned value.

Abstract: In a digital image forming apparatus, a document image is read as digital data, and an image type of bi-level image or multi-level image is discriminated from the digital data. For a bi-level image, an intensity of laser beam for exposing a photoconductor is modulated according to the image data with a duty ratio of 100%. On the other hand, for a multi-level image such as a photograph image, the intensity of laser beam is modulated with a duty ratio in the unit of two or more dots according to the image data. The duty ratio and the laser output power are changed according to a type or document image or according to sensitivity characteristic of the photoconductor.

Abstract: Optimally determined halftoning algorithms are applied to tone values by selecting among combinations of at least two algorithms that best address the tradeoff between output quality and rendering performance. Input tone values are scrutinized and matched with the algorithm combination that processes the associated tone values in a manner that increases performance (including data compressibility) without sacrificing output quality. The selection process is computationally simple and fast. Reliability is ensured because the combinations of halftoning algorithms are tabulated as a result of analysis of test samples of the printed output.

Abstract: A method and device for processing image data for a document includes the steps of reading RGB image data for the document; dividing the document image data into a plurality of blocks including a prescribed pixel matrix; calculating an average value information and a gradation range index for each of the blocks; converting the data for each pixel of each of the blocks into coded image data based on the average value information and the gradation range index so that the coded image data defines each pixel with fewer gradation levels than the original image data; storing in a memory unit the gradation range index and coded data, which were obtained for each block through the converting step; forming letter distribution histograms for a primary scanning direction and a secondary scanning direction for each block determined to belong to a letter image; identifying a direction in which letters of the document are aligned based on a number of change points in the histogram for the primary scanning direction and a n

Abstract: Improved image enhancement methods are disclosed which may be performed on conventional video processing systems. These methods operate in real time to improve the appearance of images as perceived by the human eye, and/or to render these images more suitable for computer analysis. A first preferred embodiment enhances color images without degrading the fidelity of the image. A second preferred embodiment enhances scanned gray-level document images by decreasing the blurring of the image and increasing the contrast between light and dark regions of the image.

Abstract: An image enhancing method using a mean-separate histogram equalization method is disclosed. An input image signal is divided into two sub-images in a picture unit according to a mean level of the input image signal. Then, cumulative density functions for each of the sub-images are calculated. Afterwards, the input sample is mapped into two gray levels, each of which belongs to a first range and a second range, by using first and second transform functions defined by use of the cumulative density functions, respectively. Finally, one of two mapped levels is selected depending on the magnitude of the input sample. As a result, the brightness of the given image can be preserved while the contrast is enhanced.

Abstract: Colored objects are represented by digitized color histograms which are used for the segmentation of digital color images. In this case, the binary values of the color histograms correspond to the decision as to whether a pixel can or cannot belong to a given object segment. Model-based parameterizations of these color histograms are preferred for the efficient execution of the segmentation. In particular, they permit adaptation of the color histograms to temporally varying lighting conditions with acceptable expense.

Abstract: A method and apparatus for generating a digital representation of an image. The apparatus includes a scanning device for scanning the image to generate digital data defining the colour content of pixels of the image. An input profile generator is provided for generating an input profile defining the NTF of the scanning device.

Abstract: In a state where no original document is set, light emitted from a light source 6 is received by a sensor 5, a integrated light quantity reference value with which an output is made to be predetermined value V0 is obtained (P1), a magnification of the quantity of light and a gamma correction table are produced from gamma function data for prescanning (P2-1), a quantity of light for prescanning is obtained in accordance with a light quantity adjustment value obtainable from the magnification of the quantity of light and the integrated light quantity reference value and prescanning of a color negative film is performed (P2-2), and an image signal obtained by prescanning is converted with the gamma correction table so as to output image data (P2-3).

Abstract: A filtering process is carried out on an image signal representing a color image and with an infinite impulse response (IIR) filter to form an unsharp image signal, which represents an unsharp image of the color image. Dynamic range compressing is performed out on the image signal in accordance with the unsharp image signal, and a processed image signal is thereby obtained. A visible image is reproduced from the processed image signal. The dynamic range compressing process can be carried out with relatively few line memories such that the apparatus for carrying out the processing may be kept small, and the printed image having good image quality can thereby be obtained.

Abstract: In the present invention statistical methods are used to estimate the reflectance of the paper and align the tone gamut to the dynamic range of a digital input device such as a scanner during a single scan. The estimate is refined during the scan. This refinement increases the robustness with respect to unfavorable originals (e.g., originals with a dark border) and at the same time also can take into account such phenomena as the change of the response of the sensor due to thermal effect during slow scans. In the present invention no spatial information on the image is collected. Instead a histogram of the occurrence of each tone level is accumulated during the scan. The background color of the image, i.e., the tone value of the paper is estimated by analyzing the histogram. When this value is known, the parameters for a tone reproduction curve (TRC) can be calculated. The shape of the TRC is not altered by these parameters, i.e., the exposure can be controlled independently of the tone reproduction.

Abstract: In an image processing apparatus, a color image is read with pixels aligned along a direction to provide first color data on the color image. The first color data includes red, green and blue data at each pixel. A first operator calculates first chroma data according to the first color data. On the other hand, a phase shift device generates second color data by shifting a phase of red data and by shifting a phase of blue data in the first color data, and a second operator calculates second chroma data according to the second color data. A selector selects chroma data having a lower chroma, and a black edge of a character a the color image is discriminated according to the selected chroma data.

Abstract: An image conversion apparatus for image-converting input color image signals, and outputting the converted signals to an output apparatus, allows execution of a plurality of different color processing operations, checks if an input color image falls within a color reproduction region of the output apparatus, and changes the color conversion processing result to be output depending on whether or not the input color image falls within the color reproduction region of the output apparatus. For example, when the input color image falls within the color reproduction region of the output apparatus, color reproduction color-matched with input color image signals is performed. When the input color image falls outside the reproduction region, color reproduction is performed by color conversion processing assuring highest color reproducibility.

Abstract: Different exposures of an electronically represented, pictorial scene are combined into a final image having expanded dynamic range yet still capturing subtle differences in exposure. The final image provides increased shadow, midtone and highlight detail notwithstanding the limited response of the system (electronic or photographic) that produced the component images. The invention features automatic identification of optimally exposed regions (on a pixel-by-pixel basis) from the component images, as well as automatic combination into a final image. The invention may also be used to make a camera, of possibly unknown response function, behave as an array of photometric measurement instruments (e.g., an array of light meters) to within a constant scale factor.

Abstract: A digital color processing method for images from scanners and digital cameras processes image data suitable for display on monitors or color hardcopies produced by digital color printers and correct hue shift and incorrect exposure based on the image content. The method automatically corrects the data based on the histogram of the acquired image normalizing the image data to correct for the hue shift and determining the gamma parameter to correct the exposure of the image.

Abstract: An apparatus for correcting contrast of a selected range without changing lightness and color tone of a pixel designated as a central object of processing.

Abstract: This invention relates to a method and apparatus for processing an image and particularly a method and apparatus for providing a function of automatically judging whether an input image is a color or monochrome image. This invention discloses various arrangements for preventing errors in the above judgement.

Abstract: The present invention relates to a method and apparatus for converting and for matching color values between color spaces. The invention comprises a source device (16) for generating image signals; a color space converter (11), including a receiving and determining means (10), an interpolating means (14), and a regular primary look-up-table (LUT) (12), for converting the received image signals into second space color values; an outputting means (18) for supplying the second color values to a peripheral device (20).

Abstract: A system for converting RGB color signals to CMY or CMYK color signals, such as to operate a color printing apparatus, utilizes three separate electronic look-up tables. Each look-up table allows inputs of RGB signals, which are applied to a three-dimensional space. Each point in the space represents an output for one CMY color signal, and each look-up table is dedicated to one CMY color output. Each look-up table emphasizes one particular RGB color, by providing a higher resolution of inputs along the axis for that color.

Abstract: A technique, applicable for use in implementing a print preview function in a color electronic imaging system, that, under a variety of different ambient lighting conditions, will yield a highly acceptable color match between a color image appearing on a CRT monitor and that which will be produced by the system as a printed version of the same image. Specifically, a computer system (120) is employed to scan an image and, through an ambient illumination sensor (27), senses the spectral content of the ambient illumination. The computer displays the scanned image along with various non-image information which can be used to adjust the color of the image. The computer transforms the color of the scanned image and the non-image information such that a resultant display of the image and the non-image information on a color monitor (24) will show the appearance of a print when the print is viewed under the ambient illumination.

Abstract: In a digital image forming apparatus, a document image is read as digital data, and an image type of bi-level image or multi-level image is discriminated from the digital data. For a bi-level image, an intensity of laser beam for exposing a photoconductor is modulated according to the image data with a duty ratio of 100%. On the other hand, for a multi-level image such as a photograph image, the intensity of laser beam is modulated with a duty ratio in the unit of two or more dots according to the image data. The duty ratio and the laser output power are changed according to a type of document image or according to sensitivity characteristic of the photoconductor.

Abstract: A method and system for compressing video in a manner characteristic of photographic film compression. One embodiment of the invention is a video camera including circuitry for compressing the raw video signals generated thereby to introduce film-like compression characteristics thereto. Such video camera preferably includes controls allowing smooth, gradual, film-like compression of video image data recorded thereby, in response to user variation of no more than a small number of compression parameters. In other embodiments, the invention is a video post-production editing system which performs film-like compression on an analog or digital video signal. Such compression can be performed to match the dynamic range of a first, film-derived video segment to that of a second, non-film-derived video segment. Preferably, the invention implements film-like compression digitally, by employing digital circuitry.

Abstract: In a digital image scanning system and method, a sample of tone values from the image is used to estimate the exposure or central tendency of the recorded image. The estimate is then used to select a tone correction function used to process the image prior to printing, transmission, or CRT display.