Abstract: There is disclosed an image reading apparatus having an image sensor unit. The image sensor unit may include a number of photodiode arrays. The photodiode arrays may have different qualities and the output of the photodiode arrays may be processed differently. Output of the photodiode arrays may be mixed to improve image qualities.

Abstract: A picture image processing apparatus is provided with a hue calculating portion for calculating a hue pixel by pixel based on RGB data, a first sampling portion for sampling pixels having a hue corresponding to a skin color from the RGB data, a first characteristic quantity calculating portion for calculating a first characteristic quantity representing a characteristic of the RGB data of the pixels, a second sampling portion for sampling the pixels located in a central part of an image area, a second characteristic quantity calculating portion for calculating a second characteristic quantity representing the RGB data of the pixels sampled by the second sampling portion, a correction amount calculating portion for calculating a density correction amount using the first and second characteristic quantities, and a density correcting portion for correcting the density of the RGB data. The density of a main subject in the image can be properly corrected.

Abstract: There is provided a patch measurement device which, even if the position of a patch in a control strip printed on a printed material is incorrectly detected, does not affect the controlling of the printing apparatus. A data storage section 271 in a patch measurement device 27 stores printed-image data Dpd. A reference mark detection section 272 detects a reference mark rm in the printed-image data Dpd, and generates position data thereof. A reference mark position data comparison section 273 compares the position data against past position data stored in a reference mark position data storage section 274 to determine the validity of the position data. If the position data is valid, a patch position detection section 275 detects a patch whose color density is to be measured. A color density measurement section 276 generates color density measurement data of the printed patch.

Abstract: An LUT1 preparation section 1 and an LUT2 preparation section 2 prepare an LUT1 and an LUT2 for producing linear output from first raw data or second raw data. Using the LUT1 and LUT2, an LUT1 conversion section 3 and an LUT2 inverse conversion section 4 convert CMYK of the first raw data and C?M?Y?K? of the second raw data into four color values adjusted, and an L matching LUT preparation section 5 prepares an L matching LUT so that the K value of the four color values adjusted becomes equal. A K preservation 4DLUT preparation section 6 prepares a K preservation 4DLUT from the four color values adjusted, the L matching LUT, and the Lab value of the first and second raw data. A 4DLUT reset section 7 resets some of data in the prepared K preservation 4DLUT, whereby partial calorimetric match is intended.

Abstract: A method for modifying an input digital image having an (x,y) array of image pixels, each image pixel having an input code value for each of four or more color channels, to produce a depleted digital image subject to a total colorant amount limit. The method includes determining depleted code values for each color channel such that the depleted code values produce substantially the input perceived color according to a device color model.

Abstract: A method for modifying an input digital image having an (x, y) array of pixels, each pixel having an input code value for one or more color channels, wherein said input code value has a nonlinear relationship to colorant amount, to form an output digital image containing output code values for each pixel subject to a total colorant amount limit.

Abstract: An image processing method matches the gradations of a first output unit and a second output unit which have different gradation-reproduction ranges. The image processing method sets first-output-unit information on the first output unit, sets output-medium information for use in the second output unit, and finds an output-gradation reproduction curve from the first-output-unit information and the output-medium information.

Abstract: In an image reading apparatus having a light source for illuminating a document, an image sensing element for outputting an electrical signal in accordance with an input light quantity, a first reference member, and a second reference member, shading correction data is acquired. A time since the light source is turned on is measured, and when the measured time does not reach a predetermined time, shading correction data is acquired by a first method using the first reference member. When the predetermined time has elapsed, shading correction data is acquired by a second method using the second reference member.

Abstract: An image processing apparatus includes a determination part, an information obtaining part, a dynamic range setting part and a processing part. The determination part determines whether or not an image includes an area where destruction of gradation due to contrast correction tends to be conspicuous. The information obtaining part obtains information of the area when the determination part determines that the image includes such an area. The dynamic range setting part sets a dynamic range using the information obtained by the information obtaining part. The processing part performs the contrast correction on the image using the dynamic range set by the dynamic range setting part.

Abstract: An image processing method and apparatus enhancing sharpness of an image while suppressing enhancement of noise components. Image data is separated into frequency components, and an evaluation value for evaluating the level of an image to be enhanced is calculated for each pixel. A gain for an intermediate/high frequency component is set in accordance with the evaluation value, and multiplied by the intermediate/high frequency component, and the frequency components are synthesized. Test images, each having a density which is different from the other but constant over the test image, are prepared and an evaluation value is obtained from each of the test images as an evaluation correction value. The evaluation value of the image for processing is corrected by subtracting the evaluation correction value corresponding to the density of each pixel from the evaluation value of the image data to be processed for each pixel.

Abstract: A multi-level error diffusion system includes a processor that creates an m by n super pixel cell as an output pixel value for individual ones of a plurality of single input pixel values that are indicative of an image. The processor assigns to individual ones of the m by n super pixel cells available printer output color values, where the average of the assigned output values are selected to be as close as possible to corresponding individual one of the single input pixel values. A multi-level printer receives the individual ones of the m by n super pixel cells having assigned output values and converts them into printer data to form a printed image.

Abstract: A printing adjustment method includes providing a plurality of solid and screened density values produced by a proofing device that represent intended density values. The method also includes providing a plurality of solid and screened density values produced by a press output device. The method also provides calculating, in response to selected ones of the plurality of density values produced by the press output device and selected ones of the plurality of density values produced by the proofing device, required percent dot values to be used to print on the press output device a plurality of adjusted density values that approximately correspond to the intended density values. In a particular embodiment, the plurality of solid density values produced by the press output device are varied approximately linearly in density along a first axis, the first axis approximately perpendicular to direction in which output of the press output device is produced.

Abstract: An image data of M-gradations in a pixel is converted into multivalued image data of N-gradations (M>N>2) in a pixel. A remarked pixel converted into the multivalued data is determined whether to be a predetermined gradation TJ (N>TJ>2) in which a tone jump occurs. When the remarked pixel converted into the multivalued data is determined to be the predetermined gradation TJ, it is determined whether a pixel of the predetermined gradation TJ exists in pixels being adjacent to the remarked pixel. When the pixel of the predetermined gradation exists, the gradation of the remarked pixel is changed to the gradation other than the predetermined gradation so as to prevent the tone jump, and an average density after multivalued image data conversion is preserved.

Abstract: An integrated processing box performs processing commonly to a plurality of input devices, a plurality of output devices, or a plurality of storage devices. For example, the integrated processing box performs noise reduction processing on data received from an input device or a storage device or data supplied to an output device or the storage device. The integrated processing box also performs processing, for example, temporal/spatial processing or grayscale processing, variably to each type of input device, each type of output device, or each type of storage device. Accordingly, if the input device is, for example, a video camera, the video camera is formed only by a CCD, a sample-and-hold circuit for sampling and holding the output from the CCD, an AGC circuit for adjusting the gain of the output from the sample-and-hold circuit, and an A/D conversion circuit for converting the analog output of the AGC circuit into a digital output.

Abstract: An image recording device includes a sub-scanning/conveyance device for sub-scanning and conveying an image recording material. An acceleration pickup for measuring acceleration of the sub-scanning/conveyance device is mounted to the sub-scanning/conveyance device and connected to a control section. When the acceleration pickup detects acceleration equal to or greater than a predetermined value, an alarm is turned on via a bus to signal a frame number of the image recording material exposed when vibration equal to or greater than a predetermined value has occurred. Image data of the corresponding image number detected by a hole sensor is inputted from an image processor to an image data storage device and stored therein. When a predetermined exposure ends, the stored image data is transmitted from the image data storage device to a light beam scanning device, and the image recording material is re-exposed in accordance with the image data.

Abstract: The present invention has an object to provide a gradation correcting apparatus for correcting the gradation of the white side of a video luminance signal. The gradation correcting apparatus is provided with a maximum value detector 101 for detecting a maximum value of a luminance signal S101, a white comparator 102 for comparing the luminance signal S101, a maximum luminance value S111 detected by the maximum value detector 101, and a first white threshold value S103, a white linear converter 103 for performing linear conversion on the luminance signal S101 on the basis of the maximum luminance value S111, the first white threshold value S103, and a second white threshold value S104, and a white controller 104 for correcting the luminance signal S101 on the basis of the result of the comparison in the white comparator 102, the output of the white linear converter 103, and the second white threshold value S104.

Abstract: An attentional portion to be corrected in gradation of an image is specified, and a gradation corrective function with respect to a density of the specified attentional portion is generated. Preset gradation conversion characteristics are corrected with the gradation corrective function, and the gradation of the image is converted according to the corrected gradation conversion characteristics. The gradation conversion characteristics can be corrected in the vicinity of a desired density.

Abstract: An image reading apparatus comprises a correction coefficient determining circuit 4 for determining a correction coefficient per each bit of white reference data in a main scanning direction which are read immediately before reading an original image, a correction coefficient modifying circuit 5 for producing a modified correction coefficient, and a correction coefficient predicting circuit 6 for producing a predicted correction coefficient with reference to the modified correction coefficient. If an absolute value of a difference between the correction coefficient and the predicted correction coefficient is smaller than and not smaller than a predetermined threshold value, the correction coefficient modifying circuit 5 produces the correction coefficient and the predicted correction coefficient as the modified correction coefficient respectively. A correction coefficient memorizing circuit 7 memorizes the modified correction coefficient as shading correction coefficient data.

Abstract: A color image processing apparatus includes at least patch image output units which output patch image data, based on patch data in a storage area, a patch data extractor which extracts read patch data by reading a patch image formed according to the patch image data, using a color scanner, a patch data processor which estimates the record gradation of patch data, based on the read patch data, and a gradation corrector which corrects a color image signal, based on the estimated record gradation and patch data. The apparatus provides gradation correction based on gradation estimated from patch data, thus making it possible to reproduce gradation and color well.

Abstract: A superposed colors graphic providing a true, continuous color fade transition between two different colors achieved by applying first and second color graphics onto respectively different side surfaces of at least one transparent substrate, each color graphic having a respective color fade. The first and second color graphics are mutually aligned such that the color fade of each of the color graphics are mutually coextensive and superposed so as to thereby provide a continuous fade between the colors. The first and second color graphics may be applied to the respective substrate side surfaces by any suitable method, such as for example by silk screening, by lithography or by decorative film applique.

Abstract: Linear chromaticity conversion is used to perform color reproduction of a liquid crystal display (LCD) compatible with a cathode ray tube (CRT). An inputted signal is subjected to processing similar to processing used in the CRT display. A light source chromaticity conversion processing portion carries out a ? correction to the signal in a ? operation portion by using ?1=?crt of the same nonlinear characteristics as the CRT, and performs an operation of a chromaticity conversion matrix in a matrix operation portion. An LCD inverse ? correction portion uses ?2 establishing ?_lcd=?lcd/?2=1 to perform an inverse ? correction to the inputted signal. An LCD ? characteristic operation portion performs a ? correction using ? characteristics of the LCD to the signal inputted from the LCD inverse ? correction portion, outputs a picture signal, and causes an image to be displayed on the LCD.

Abstract: In order to carry out gradation drawing processing without causing deterioration of printing processing throughput, i.e., deterioration of printer engine performance, in the event that a received drawing command is a gradation drawing command, the degree of change of color within the gradation drawing area is obtained, and a thinning-out level within the gradation drawing area is determined, based on the obtained degree of change of color. An enlargement value is determined based on the thinning-out level decided upon, and instructions are given to an image processing unit to draw the gradation drawing area in a manner enlarged with the enlarging value decided upon. Next, the color values of the pixel values within the gradation drawing area are calculated at pixel intervals determined by the thinning-out level, and this is used as gradation data.

Abstract: Image data supplied to an image forming apparatus are converted into image data linearly correlated with the image density, and the image ratio is calculated by dividing the number of pixels in which the toner is deposited during image formation based on the thus-converted image, with a value obtained by multiplying the total pixel number corresponding to the size of the print medium with the number of gradation levels per pixel. Then the toner amount consumed in the image formation based on the entered image data is determined by multiplying the image ratio, the size of the print medium to be used and the toner amount consumed per unit area in a solid image formation.

Abstract: An image management system is proposed that can display the same image in the same appearance on each image display device connected to a network independent of individual hardware characteristics. When an image file server that manages diagnostic images transfers the diagnostic image to an image display device connected to the network, it transfers a gradation table describing a gradation correction curve corresponding to the type of display of the image display device to be a destination as well. On the side of the image display device, the diagnostic image will be displayed in the same appearance independent of local characteristics such as hardware or the like by performing luminance correction on the diagnostic image referring to the received gradation table.

Abstract: The present invention provides a unique method, apparatus, system and storage medium for image binarization process, wherein an image to be processed is divided into a plurality of sub-images and an binarization threshold for each of the sub-images is determined based on the gray-levels of the edge pixels detected in respective sub-image. The image processing method of the present invention comprises: calculating a gray-level statistical distribution of pixels of an image, detecting edge pixels in an image based on an edge criterion corresponding to the gray-level statistical distribution, dividing the image into a plurality of sub-images; determining a binarization threshold for each of the sub-images based on the gray-levels of edge pixels detected in the sub-image; and performing binarization process for each of the sub-images based on the binarization threshold of the sub-image.

Abstract: In a digital printing process employing a CTP device 14, hues can easily be changed in a process of generating printing plates without going back to a prior process. A plurality of gradation conversion curves whose gradation characteristics are different stepwise from each other, which are stored in a gradation conversion curve saving unit 22, are displayed on a display unit 36. The user selects a desired of the displayed gradation conversion curves with respect to at least one color element with a keyboard/mouse 34. The selected gradation conversion curve is set in an LUT converter 26. Input image data G can easily be converted into output image data Ga by converting the gradations of the input image data G according to the gradation conversion curve set in the LUT converter 26. The image data Ga is converted by a binarizing unit 30 into binary image data H, which is supplied to the CTP device 14. The CTP device 14 outputs printing plates each bearing a binary image represented by the binary image data H.

Abstract: The tone reproduction curve is smoothed to eliminate or reduce artifacts due to abrupt changes in the final system tone reproduction curve. As the tone reproduction curve approaches an end point, it is modified, if necessary, so that the angle between a tangent to the tone reproduction curve at a point, and a line from that point to the end point is less than a threshold value. The end point is considered to be a corner of a box, the threshold value is a function of the distance from the point to the nearest of the walls of the corner, and the threshold value goes to zero as the distance to the wall goes to zero. Thus, the tone reproduction curve is guided to the end point in a smooth and monotonic fashion.

Abstract: To provide an image processing apparatus capable of making an MTF correction for each image at a low cost. The image processing apparatus according to the present invention performs a spatial filtering process by selecting a filter having an appropriate spatial frequency characteristic for each area according to an image area determination signal and a color gamut determination signal for an input color image signal. Furthermore, an image signal is divided into blocks for each image area, and an appropriate spatial filter is selected for each block depending on the ratio of blocks of each image area to the entire block. Thus, an appropriate filter can be selected depending on the characteristic of an image, and an appropriate MTF correction can be made without largely changing a conventional configuration.

Abstract: An integrated processing box performs processing commonly to a plurality of input devices, a plurality of output devices, or a plurality of storage devices. For example, the integrated processing box performs noise reduction processing on data received from an input device or a storage device or data supplied to an output device or the storage device. The integrated processing box also performs processing, for example, temporal/spatial processing or grayscale processing, variably to each type of input device, each type of output device, or each type of storage device. Accordingly, if the input device is, for example, a video camera, the video camera is formed only by a CCD, a sample-and-hold circuit for sampling and holding the output from the CCD, an AGC circuit for adjusting the gain of the output from the sample-and-hold circuit, and an A/D conversion circuit for converting the analog output of the AGC circuit into a digital output.

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. The sigmoidal function has the form: t ? ( x ) = 100 1 + exp ? ( - ? ? ( x / 100 - ? ) ) , where ? is the slope parameter and ? is the shift parameter. The input value x in the sigmoidal function varies in the range [0, 100], because the tone curve is generated on an L* scale, which has values from 0 to 100.

Abstract: An image processing apparatus substantially performs image processing on an image including first gray-scale conversion processing using a first gray-scale conversion curve. Then, the image processing apparatus performs second gray-scale conversion processing on the processed image using a second gray-scale conversion curve, and displays a composite gray-scale conversion curve combining the first and second gray-scale conversion curves.

Abstract: In the case of color purification, images do not appear unnatural even by an input profile other than a certain particular input profile, no considerable labor is required for creating profiles and no large memory area is required for storing the profiles. A color conversion method includes holding a color space used for color conversion for color data having specific color space characteristics in advance, comparing color space characteristics of the inputted color data with color space characteristics of the color space held in advance, performing color conversion using gradation characteristics of the inputted color data and a color space of the inputted color data when a difference between the color space characteristics is a set threshold level or less, and performing color conversion using the gradation conversion data of the inputted color data and the color space held in advance when the difference is over the set threshold level.

Abstract: An image processing method for extracting a characteristic amount of a photographed image from the photographed image obtained by photographing an object, comprises a passing through deleting step of deleting a passing through area from the photographed image, a preparing step of preparing a projection from the image from which the passing through area is deleted, and a setting step of setting a characteristic area of said photographed image based on a result of the projection.

Abstract: A color correction device for correcting colors in a color image comprises: coordinates for registering points in a first color space of at least one standard point, the first color space having axes for specifying colors; a second set of coordinates for registering points in a second color space of at least one standard point, the second color space having coordinates that include at least one coordinate for specifying color hue; a translator to convert image data of at least one point in the first color space to coordinates in the second color space; a modifier for modifying at least hue within image data in the second color space to form corrected image data in the second color space; and a translator for transferring corrected image data in the second color space to corrected image data in the first color space.

Abstract: An image processing apparatus includes an edge detecting portion for detecting an edge area of an input image signal and a lightness and chroma detecting portion for detecting a low lightness and low chroma area of the input image signal. An image processing such as edge emphasizing is performed for the edge area of black letters or lines decided by the detection signals of the edge detecting portion and the chroma detecting portion. The image processing apparatus further includes an edge enlarging portion 6 for enlarging the edge area detected by the edge detecting portion 4 and circuits 12 and 19 for converting color image data C, M and Y and black image data K so that C, M and Y color densities in the enlarged edge area is decreased and a black densities is increased. Thus, supporting a high definition, color drift in the edge portions of the black letters or lines of the color image becomes inconspicuous, so that the reproducing quality is improved.

Abstract: A construction is achieved at low cost which reduces the loss of gradation in a dark portion of an image that has been subjected to gamma correction in accordance with characteristics of a display. In an image reading apparatus, to make it possible to more finely reproduce the gradation in the dark portion, the number of gradations expressed by an signal obtained by a CCD is reduced by performing non-linear gamma correction using a gamma coefficient below one, and the resulting signal is transferred to a computer serving as a host computer. In the computer, the transferred signal is subjected to gamma correction using a gamma coefficient that is an inverse of the gamma coefficient used in the image reading apparatus, thereby canceling out the influence of the gamma correction performed in the image reading apparatus.

Abstract: A video processing method comprises the steps of dividing an entire input data region into three of first, second and third regions in order from the low level side thereof; setting, as an output data characteristic to input data, a trapezoidal characteristic which is nonlinear and continuous as a whole and consists of a linear portion in the first region where the gain is greater than one, a linear portion in the second region where the gain is equal to one exactly or approximately, and a linear portion in the third region where the gain is smaller than one; setting, as another output data characteristic to the input data, an S-shaped characteristic which is nonlinear and continuous as a whole and consists of linear portions in the first and third regions where the gain is smaller than one, and a linear portion in the second region where the gain is greater than one; selecting either the trapezoidal characteristic or the S-shaped characteristic; and correcting the digital luminance data in accordance with th

Abstract: A system and method for detecting text edges in digital document images utilizes filters that process the luminance and/or chrominance values within a selected region of the image to determine whether a given pixel of the selected image region is a text edge. The filters are configured to determine the gradient, the curvature, the maximum luminance value, and/or the maximum chrominance value for the luminance values within the selected region of the document image. Two or more of these indicators are used to detect text edges in the document image.

Abstract: When an image forming means forms a reading gradation pattern chart, gradation patterns are formed so as to prevent an intensified electric field caused by a potential difference at a boundary of an electrostatic latent image on the gradation patterns, which are adjacent to each other in a sub-scanning direction of an image forming section. With this arrangement, an image forming apparatus for suitably correcting the gradation pattern can adjust image forming conditions in a positive and appropriate manner.

Abstract: The image processing apparatus and the photoprinter include a condition setting section for setting image processing conditions by analyzing image data, an image processing section for executing image processing in accordance with the image processing conditions set in the condition setting section, a mode setting an section including a plurality of operation modes, setting a operation mode from among the plurality of operation modes and changing at least one of a processing content in the condition setting section and a content of the image processing executed in the image processing section in accordance with the thus set operation mode, and optionally a selection device for selecting the operation mode.

Abstract: To allow high-speed image data generation processing by shortening time required to generate an object having a predetermined gradation pattern over a number of lines in the vertical or horizontal direction in gradient fill object drawing processing, an image processing apparatus of this invention detects the number of lines of gradation in the horizontal or vertical direction, calculates only the first line of detected gradation, copies the calculation value of the first line, and embeds it in the second and subsequent lines, thereby shortening time required to generate objects of the second and subsequent lines and allowing high-speed generation processing.

Abstract: The present invention addresses problems encountered in the conversion of continuous tone data into binary data for printing on low resolution imaging systems. Representation of the continuous tone data is only roughly approximated through the conversion to binary data. Artifacts of the binary printing process are objectionable for several reasons. They decrease over all image quality and may sometimes allow for only partial representation of the original data. Partially formed and/or irregularly formed text characters are one such example. This invention addresses this problem by forcing certain levels to be processed through predictable dot dispersion patterns so as to preserve pre-identified portions of the input data stream. Continuous tone image data for imaging on a digital output device is processed by identifying at least one problematic tone level in the binary representation of the image, and identifying at least one non-problematic tone level in the binary representation of the image.

Abstract: In a recording device, electrostatic recording units of Y, M, C and K are arranged along the direction of the feed of a recording sheet by a belt unit. The device forms latent images corresponding to image data by optical scanning of an exposure device onto a rotating photosensitive drum, develops the latent images with toner components having different colors, and then transfers the developed images onto the recording sheet on the belt unit. A color matching processing unit performs color matching processing including color slippage correction of different color images. An automatic color matching mode processing unit works the color matching processing unit when conditions beforehand decided in the state that an automatic correction mode is set up are realized.

Abstract: In a copying machine connected to the network, calibrations on the printers are performed as follows. When an execution of calibration is requested, the copying machine displays all identification numbers of the printers connected to the network on the operation panel of the copying machine. When the user selects a printer to be calibrated through the display, the copying machine causes the selected printer to output a specified test pattern. Then the copying machine reads the test pattern, generates a correction table and registers the generated table with the printer.

Abstract: The present invention relates to an image processor and an image processing method for compensating gradation by effectively avoiding drop of partial contrast through application to an image processor such as television receiver, video tape recorder, television camera and printer or the like. A domain to which an input image data belongs is judged, for example, with reference to the low frequency element r (i, j) of the pixel value x (i, j) and the signal level x (i, j) of the image data forming an input image VT is compensated on the basis of the result of judgment r(i, j).

Abstract: It is difficult properly to perform correction processing such as white balance adjustment and exposure compensation for all types of images. This invention provides a way in which white balance adjustment and exposure compensation are performed in accordance with image features by considering the arrangements of pixel values in the highlighted and shadow areas of an image. Proper correction processing can therefore be performed for any types of images.

Abstract: A gradation patch image Ip used for determination of tone characteristics of an apparatus is progressively varied in the tone level thereof from the maximum tone level (level 255) to the minimum tone level (level 0). The gradation patch image is either a toner image continuously and consistently varied in the tone level thereof or a toner image having the tone levels varied stepwise at a smaller pitch than a width of a detection region of a patch sensor. In density detection of such a gradation patch image Ip, toner image densities at portions on either sides in the detection region of the patch sensor are canceled each other out by averaging and hence, only a toner image density substantially at the center of the detection region can be obtained.

Abstract: An image processing method for creating a reproduced image by executing image processing on digital image data obtained by a digital camera. This method determines first a density conversion condition for the digital image, determines next a gradation conversion condition for the image on the basis of the density conversion condition, modifies the digital image on the basis of at least one of the density and the gradation conversion conditions, and thus creates the reproduced image. The method may initially separate the digital image data into density component data and color component data, determine the density and gradation conversion conditions by using the density component data instead of the digital image data, modify the density component data in accordance with the density and gradation conversion conditions and synthesize the modified density component data with the color component data.

Abstract: The present invention performs gradation conversion linearly on an image signal when the image signal is darker than a preset value. Consequently, the dark region of the image is not distorted nonlinearly, and the gradations of shadows and hair can be reproduced in full richness. On the other hand, gradation conversion is performed nonlinearly on image signals if the image signal is brighter than a preset value. The nonlinear conversion in this case: (1) has a slope that effectively equalizes an average noise amplitude of the image signal without being based on the output gradation value, and (2) is offset so as to be continuous with the gradation conversion characteristic of the dark area gradation conversion unit. Through condition (1), the level-dependent noise in the bright region is equalized. Furthermore, through condition (2), gradation differences and gradation reversals do not occur at the boundary between the dark region and the bright region.

Abstract: An automated method of improving digital color images at high speed, which supports pipe-lining and has very little memory requirements, and is therefore specially suitable for on-the-fly processing of real time video, as well as for processing of large batches of images without the need of human intervention. The method includes a novel dynamic range adaptation scheme that operates on the norm of the image, which is suitable as is for gray-scale images. For, color images, a simple color reconstruction stage is added that maintains optimal color fidelity.