Abstract: An image condition is judged based on a mean value and a standard deviation of a feature quantity of an image, and image correction information in the image condition is created based on the mean value and the standard deviation, to thereby correct the image, based on the created image correction information. In this manner, parameters for the image correction processing are determined automatically and highly accurately corresponding to the feature quantity of the image, and the image correction processing is performed based on the parameters. Therefore, the image quality can be improved, while considerably reducing the labor of the operator who performs the image processing.

Abstract: A shading correction circuit is disclosed which prevents unevenness and partial dull of an edge caused by noise which remains when noise is sliced using a fixed value as a threshold level to be used for distinction between noise and an edge component. The shading correction circuit includes a level correction circuit for correcting a level of shading, and a noise removal circuit for receiving a level adjusting coefficient used by the level correction circuit and controlling the slice level of level slice to be used to remove an edge component mixed in a noise component with the level adjusting coefficient.

Abstract: A digital camera which is an image processing apparatus is controlled so that a first image and a second image are acquired for the same subject in different timings. A plurality of correction tables for use in shading correction are prepared in advance in a shading ROM of the digital camera. When a first image and a second image are acquired, multiplication of one correction table is performed on both images by a shading correction circuit. As a result of this, a shading correction is effected on both images. The first image and the second image that have been subjected to the shading correction are taken into respective image memories, and after being subjected to a positioning process by a general controller, they are synthesized to generate a synthesized image.

Abstract: Apparatus and method of correcting for dark current in a solid state image sensor, include capturing an image with the image sensor to produce a digital image having pixel values; correcting the pixel values with a dark level correction value; employing a control system to adjust the dark level correction value to drive the number of pixels having values lower than a predetermined value chosen to represent dark scene content to a predetermined range.

Abstract: An image input apparatus has an image sensor for photoelectrically converting image information of an object into an electric signal and outputting the signal, and a correction circuit for adjusting a fluctuation of offset components generated during photoelectric conversion contained in the signal output from the image sensor to correct the offset components. Images of good quality can be obtained by correcting the offset components contained in the signal output from the image sensor.

Abstract: An imaging device is calibrated using a flat, featureless surface and uniform illumination, relying on the effect of off-axis illumination and vignetting on the reduction of light into the camera at off-axis angles. The effect of the tilt of the camera is also considered. These effects are used to extract intrinsic camera parameters including focal length, principal point, aspect ratio and skew.

Abstract: Disclosed is an image sensing apparatus having a function of removing a dark current noise component of an image sensor. This image sensing apparatus includes an image sensor such as a CCD, at least two noise component storage areas, a CPU for controlling an operation of writing a noise component of one frame generated by the image sensor into a noise component storage area selected from the at least two noise component storage areas, and a subtracter for correcting an object image photographed by the image sensor, on the basis of the noise component stored in one of the at least two noise component storage areas.

Abstract: An image processing method for compensating for light falloff in a digital image provides individual compensation values to correct light falloff in the image pixels of an input digital image; however, the individual compensation values induce a balance change in the digital image. Therefore, a balance value is determined for correcting the balance change of the digital image and the individual compensation values and the balance value are applied to the pixels of the input digital image to provide a corrected image having compensation for light falloff with minimal change to the light balance.

Abstract: A digital camera includes: an image-capturing device which captures an image of a photographic subject which passes through a photographic lens, and outputs image data; a gain adjustment section which performs gain adjustment by multiplying the image data output from the image-capturing device by a predetermined gain; a detection section which detects an optical axis of the photographic lens upon the image-capturing device; and a gain adjustment coefficient calculation section which calculates a gain adjustment coefficient according to distance between a position of a part of the image on the image-capturing device and the optical axis, and the gain adjustment section performs gain adjustment of image data corresponding to the position of the part of the image on the image-capturing device using the gain adjustment coefficient.

Abstract: A digital camera whose lens is detachable, comprising a judging section for judging whether an image failure is caused due to dirt adhering on an image sensor device unit including image sensor device, an illuminating member which is disposed in the vicinity of the image sensor device unit such that irradiation light can enter the image sensor device and which is driven when at least the judgment is made, a memory for storing a position of a picture element of the image sensor device corresponding to image sensor data causing image failure when the judging section judged that image failure has been caused, and a correcting section for correcting the image sensor data output from the image sensor device unit based on picture element position data stored in the memory when a picture is photographed after the lens is interchanged.

Abstract: From horizontal and vertical coordinate values HC and VC of a pixel, a distance operation unit calculates a distance value RV indicating the distance from an optical-axis position to the pixel. A correction-data operation unit receives the distance value RV, and calculates correction data CD for the pixel by referring to an approximation function indicating relation between distance values and correction data. The approximation function is divided into a plurality of segments, and in each segment represented by a quadratic function defined by a predetermined number of sample points.

Abstract: A method and system using a sensor array includes a programmable analog/multi-level memory array for modifying individual outputs from elements in the sensor array in order to obtain a desired sensor array output. The memory array can be programmed with data corresponding to desired modifications, such as low and high offset voltage correction, low gain correction, and gamma correction. Consequently, by utilizing arithmetic circuits, the adverse effects of corrupted elements in a sensor can be corrected by re-programming the memory array with different modification data as the need arises.

Abstract: In an X-ray film image reading apparatus, dark output distribution data of a CCD line sensor is corrected by using correction data. In order to suppress the influence of random noises on the correction data, a dark distribution correction data calculation circuit 10 calculates an average value or mode value of dark distribution outputs of all or some pixels of a CCD line sensor or a dark distribution output of the CCD line sensor subjected to a spatial low-pass filtering process, and stores it in a dark distribution memory as correction data. Next, a light source is turned on, and a subtractor subtracts the stored correction data from an output of the line sensor read from an X-ray film while the light source is turned on.

Abstract: A method for correcting a deficient image signal without lowering the resolution of a display page. The method includes generating an image signal of a subject pixel and image signals of peripheral pixels arranged about the subject pixel. A maximum level and a minimum level of the image signals of the peripheral pixels are detected. The method generates a first reference value by adding a first offset value to the maximum level and a second reference value by subtracting a second offset value from the minimum level. The method further includes generating a correction signal using at least one of the image signals of the peripheral pixels, and replacing the deficient image signal with the correction signal when the level of the image signal of the subject pixel is greater than the first reference value or less than the second reference value.

Abstract: A method for compensation at least one digital image for light falloff. The digital image may be generated for example from a conventional image frame on a film roll. A plurality of pixel values is provided for each of at least one digital image. A light falloff compensation function is applied and according to that a light falloff correction parameter is determined. Both the light falloff compensation function and the light falloff correction parameter are used to generate an individual compensation value for each pixel element. The compensation value is applied to each pixel element. The method is also able to differentiate and correct the images according to light falloff generated by pure lens falloff or a light falloff generated by the lens and the flash falloff.

Abstract: There is provided an image pickup device in which an overall output image can be prevented from being affected by an image signal of a mask area. According to the image pickup device, a prescribed area in a pickup image is masked to keep the masked area non-displayed in the output image, and the image signal of the mask area is removed from a detection target for image processing to prevent the image signal of the masked area from affecting the image processing on the overall image, whereby the image processing such as automatic exposure processing, automatic white balance processing, etc can be properly performed and the image quality of the output image can be enhanced.

Abstract: Apparatus for image capture via a blemished sensor, comprising: a large area pixel based image sensor being actuatable to move between a first image capture position and a second image capture position, an image capture controller for controlling said sensor to move between said image capture positions during an image capture operation thereby to take a sub-image at each one of said positions so that each part of an image subject is captured by at least two separate pixels of said sensor, and an integrator, associated with said sensor, for integrating said sub-images into a single full image. Preferably, the sensor is tested to find blemish positions and a shift is calculated that minimizes the number of blemish positions that superimpose between the two pixel positions.

Abstract: A correction circuit 50 is provided to correct the luminance shading caused by uneven thickness of the liquid crystal layer in the LCD panel. The correction circuit 50 generates a correction signal obtained by modulating the gradually changing signal with smaller amplitude at positions closer to the center in the horizontal direction of the LCD panel and with smaller amplitude at positions closer to the center in the vertical direction when the signal is seen vertically. The signal in the lowfrequency range components of the video signal is used for such modulation. After addind the correction signal from the correction circuit 50 to the video signal by the adder 51, the signal is processed for AC driving and then supplied to the LCD panel section 10. By thus superimposing the correction signal on the video signal for the LCD panel, the luminance shading can be corrected.

Abstract: To correct the gray levels or pixel intensities of images provided by a digital infrared camera having a two-dimensional array of detector elements with non-sensitive areas therebetween, correction coefficients respectively allocated to the detector elements are stored in a memory of an image processing system. The gray levels of image pixels are corrected by the respective corresponding correction coefficients. The correction coefficients are progressively updated and improved by means of a dynamic correction process. To distinguish stationary features in a scene being viewed from non-uniformities among the detector elements so that such stationary features do not influence the updating of the correction coefficients, the image of the scene incident on the detector is moved relative to the detector, by means of a microscanner deflecting the image beam incident, on the detector.

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: The present invention is a method of processing a digital image that is initially represented by digital data indexed to represent positions on a display. The digital data is indicative of an intensity value Ii(x,y) for each position (x,y) in each i-th spectral band. A classification of the image based on its dynamic range is then defined in each of the image's S spectral bands.

Abstract: The present invention is a method of processing a digital image that is initially represented by digital data indexed to represent positions on a display. The digital data is indicative of an intensity value Ii(x,y) for each position (x,y) in each i-th spectral band.

Abstract: An image obtaining method and apparatus for an endoscope, wherein the S/N ratio of an observation image formed from the image signal obtained by a solid state image obtaining element equipped with a charge multiplying shift resistor is improved. A signal charge representing a fluorescent image is obtained of the fluorescent image formed of the fluorescent light emitted from a target subject upon the irradiation thereof by an excitation light emitted from an illuminating means, by a charge multiplying shift resistor. A readout means reads out the signal charge and outputs an image signal based on the read out signal charge. In obtaining an observation image signal based on the read out image signal, a computing means subtracts the dark noise image signal component from the read out image signal to obtain the observation image signal.

Abstract: In an image input apparatus having an image sensor composed of plural chips, the stepwise difference in density on a chip boundary is made inconspicuous by a few compensation memories.

Abstract: The invention is an image pickup apparatus comprising an LE-SE buffer for storing multiple images with different exposure amounts that have been taken with a CCD, an SL synthesizing circuit for performing Super Latitude (SL) processing for the multiple images to generate a synthesized image with a wide dynamic range, a suitability evaluating circuit for evaluating whether the photography scene is suitable for performing SL processing with the SL synthesizing circuit, an image quality evaluating circuit for comparing the synthesized image with the images before synthesizing and evaluating image quality, and a recording format selecting circuit for which of the multiple images before synthesizing and the synthesized image to be recorded by a recording circuit, based on the image quality evaluation results and operating input from a key input circuit.

Abstract: A digital camera which is an image processing apparatus is controlled so that a first image and a second image are acquired for the same subject in different timings. A plurality of correction tables for use in shading correction are prepared in advance in a shading ROM of the digital camera. When a first image and a second image are acquired, multiplication of one correction table is performed on both images by a shading correction circuit. As a result of this, a shading correction is effected on both images. The first image and the second image that have been subjected to the shading correction are taken into respective image memories, and after being subjected to a positioning process by a general controller, they are synthesized to generate a synthesized image.

Abstract: An image signal processing apparatus to realize signal processing system and apparatus constitution, where an image signal inputted using a photoelectric conversion element such as a CCD or a contact type image sensor is obtained in circuit constitution of small scale with high picture quality. In order to solve the problems, data width of a signal referred to in a shading corrector, an MTF corrector and an error diffusion circuit is made b+f+j≦8 per one pixel. Or error component commonly possessed by plural pixels (N pixels) in the error diffusion circuit is made b+f+j′≦8, data width per one pixel being made j′=j/N. Image signal processing is realized in this constitution, thereby data width of a signal referred to in respective signal processings is reduced, and an image signal satisfying accuracy of signal processing sufficiently and having high picture quality can be obtained.

Abstract: This invention has as its object to eliminate sensitivity nonuniformity on the plane of an image sensing element irrespective of exchange of a lens. To achieve this object, in an image sensing apparatus which has an image sensing element and can exchange a lens, a memory stores shading correction coefficients respectively corresponding to pixels in a two-dimensional matrix on the plane of the image sensing element, and a correction device makes a correction calculation of pixel data read out from each pixel of the image sensing element by extracting the shading correction coefficient associated with the corresponding pixel from those stored in the memory.

Abstract: Front-ends for CCD cameras are known which use a clamping part and a sampling part using parallel arrangement of a coil and a resistor. As coils are almost always bulky they can not be integrated.

Abstract: Image-dependent tone and color reproduction processing of digital images is accomplished by creating a spatially blurred and sub-sampled version of the original image, and applying knowledge of the capture device physical characteristics to obtain statistics related to the scene or original captured. The statistics are used for image-dependent linearization of the captured image data based on an OECF model, and in conjunction with information about the output medium, to calculate image-specific preferred tone reproduction curves based on a preferred reproduction model. These curves may be applied to the red, green, and blue channels of RGB-type images to produce preferred tone and color reproduction, or to the luminance channel of luminance-chrominance type images to produce preferred tone reproduction. Alternately, the linearized image data may be reproduced directly.

Abstract: An image signal correction device comprises a shading correction circuit, a shading correction data memory and a defective pixel detecting circuit. A shading correction data corresponding to each of the pixels forming an image signal, outputted from a CCD, is stored in the shading correction data memory. In the shading correction circuit, the image signal is subjected to a shading correction in accordance with the shading correction data read from the shading correction data memory. The shading correction data is a 256-gradation data, for example. In a memory area corresponding to the highest gradation level in the shading correction data memory, the shading correction data is replaced with a defective pixel data, showing that the corresponding pixel is a defective pixel. When a defective pixel is detected by the defective pixel detecting circuit, a delay circuit is actuated, so that a pixel data, having no defect, is outputted from the delay circuit in place of the defective pixel data.

Abstract: An electronic imaging device employs black pattern correction for dark current in a charge transfer image sensor. The sensor is composed of image pixels having a characteristic black pattern of dark current in which the amplitude of the dark current for each pixel is dependent upon exposure time. A reference dark frame exposure is captured from the image sensor in the absence of light and dark frame pixel values are obtained. An exposure section regulates the exposure time of image light upon the image sensor and provides a corresponding plurality of image frame exposures; the image sensor thus generates a corresponding plurality of image frames each comprised of image frame pixel values. A processor then generates a correction factor from the dark frame pixel values and applies the correction factor to the image frame pixel values for the plurality of image frames to obtain corrected image frame pixel values that are modified for the black pattern.

Abstract: A hand held label reader is capable of illuminating a label, capturing a digital image of two-dimensional information indicia on the label, and decoding the digital image to provide decoded output data to a terminal. The target label is illuminated by a low variation illuminator that includes a circular LED array mounted behind a plano-concave dispersing lens. The automatic electronic camera, which includes a CCD camera and control circuitry, uses three images to adjust the intensity of the digital image and store a properly exposed image of the label in video RAM. The intensity of the digital image is adjusted by controlling the video system gain via adjusting the CCD array's integration time, the gain of a video amplifier, and the gain provided by an analog-to-digital converter. The gain provided by the analog-digital-converter is adjusted to compensate for the attenuation of light through the camera's lens assembly. For the first image, the digital image is obtained using a default setting for the gain.

Abstract: The image reading device has a white level correction coefficient calculation processor, in which a white level correction coefficient, used when performing a shading correction, is calculated for each pixel data outputted from a line sensor. An exposure measurement is performed so that a color correction coefficient is calculated. A combined correction coefficient, i.e. a product of the white level correction coefficient and the color correction coefficient is obtained, and a pre-scanning operation is performed to obtain pixel data. The pixel data is multiplied by the combined correction coefficient, so that the shading correction and the color correction are performed simultaneously as a combined correction.

Abstract: A method for calibrating a multi-chip image sensor, and an imaging system having a multi-chip sensor that includes color correction factors generated by such a method. The image sensor is successively controlled to image three different test targets. After imaging each target, a set of correction factors is generated and used to correct image signals generated when imaging the next test target. A first set of correction factors corrects for pixel-to-pixel variations between imaging elements in the array. The second set of correction factors corrects for chip-to-chip variations between chips in the array. The third set of correction factors corrects for array-wide variations compared to a standard color chart.

Abstract: Compressing graphic data for a first computer system, e.g. an emulated system, on a second computer system. For each scanline of the graphic data for the first computer system, a number of colors present on the scanline are counted. A new color palette for the scanline is formed at a reduced representation. Then, a representation of each color of each pixel on the scanline is converted to the new palette. The scanline is then run-length encoded. The graphic data is compressed so that it can be, for example, transmitted between a client (e.g. an X client) and a server (e.g. an X server) and conserve network bandwidth.

Abstract: White shading of an image signal is corrected by a white shading correction system which requires a small amount of memory. Rather than storing correction signals for an entire image frame for each possible condition of zoom lens position and iris opening degree, the present system stores correction signals for a single frame corresponding to a single condition where the zoom lens is at a medium position and the iris is at a medium opening degree. The present system also generates a set of correction factors corresponding to each possible condition of zoom lens position and iris opening degree. When the conditions of zoom lens position and iris opening change from their medium values, the correction signals used for correcting the image data picked up by the camera are modified by the appropriate correcting factor prior to performing correction of the picked-up image data.

Abstract: When an array of photodetecting elements has to be calibrated, normally a reference surface is scanned. Yet the reference surface is not an ideal surface and likely may include scratches or dust particles so that the signals read out from the array have to be corrected. A method and system of correction are provided in which the statistical distribution of the signals read out over the surface is evaluated for each photodetector. By this evaluation, dust and scratches can be disregarded before calculating a mean value representative of the sensitivity of each individual element.

Abstract: Shading correction is achieved with high precision while reducing the amount of data representing a correction factor for shading correction. A correction factor C(x-1) at a pixel address "x-1" is held in a latch circuit. The correction factor C(x-1) is fed to an adding circuit through a changeover switch. A differential correction factor V(x) representing the difference between the correction factor C(x-1) for a pixel addressed by "x-1" and a correction factor C(x) for a pixel addressed by "x" is read out from a differential correction factor memory, and is fed to the adding circuit. The correction factor C(x-1) and the differential correction factor V(x) are added together in the adding circuit, and data obtained by the addition C(x-1)+V(x) is outputted as the correction factor C(x) at a pixel address "x".

Abstract: An image processing apparatus is furnished with (1) a tabletop main body, (2) a readout scanner, attachable to and detachable from the main body, for outputting readout image data, (3) a portable memory pack, attachable to and detachable from the scanner, for storing image data from the scanner, and (4) a control section for, when the portable memory pack and main body are connected to each other, controlling the main body and memory pack in such a manner that the latest first correction data stored in the main body are transmitted to the memory pack to update second correction data stored in the memory pack, so that the image data in the pack memory are corrected based on the updated second correction data. Thus, the portable memory pack of the present image processing apparatus obviates measuring means for measuring correction data, and therefore, can be downsized.

Abstract: A method and apparatus for reducing bloom in output of a charge coupled device (CCD) image sensor is disclosed. The method includes the step of toggling at least two phases of said CCD after exposure of said CCD. The method and apparatus are particularly useful when a flash of light occurs during the exposure.

Abstract: An Adaptive Discrete Cosine Transformation is widely used for orthogonally transforming image data. The number of adders necessary for sum-of-product operations in a matrix multiplication is reduced. A high speed matrix multiplication and a progressive image build-up are realized by minimizing the number of operations by skipping those for insignificant data. This invention speeds up the operations for restoring image data, minimizes the necessary circuit size, and enables a progressive image build-up to be performed efficiently.

Abstract: The device includes systems for picking up (1), acquiring (2) and digitizing (3) a distorted source image (SI), a system for processing digital images (4, 47) for constructing a distortion-corrected target image (TI) corresponding to the source image (SI), this system including a first sub-assembly (4) for predetermining, on the basis of the data of a distorted TEST source image (SG.degree.), an optical center (OC.sup.n) and a polynomial function (F.sub.n) for correcting radial distortions around this optical center, and a second sub-assembly (47) which applies the polynomial correction function to each address of the pixel of the target image (TI) for furnishing the address of a point in the distorted source image (SI) in which an intensity data is present which is applied to the initial address in the target image. The method includes the computation, in a TEST source image (SG.degree.), of an optical center (OC.sup.n) at the center of optical distortions, and of a polynomial function (F.sup.

Abstract: The shading correction is performed with respect to a signal "A" indicative of the image density read by an optical read device in accordance with a reference signal "B". Both the signals "A" and "B" consist of n bits. An inputted signal having an initial value "A" is doubled by a multiplier when A=B and B.noteq.0. A subtracter subtracts the reference signal "B" from a signal "X" outputted from the multiplier and discriminates whether or not a signal "X-B" is negative. An S/P conversion register doubles an integrated value "S" having an initial value "0" and changes the integrated value from "S" to "2S" when the signal "X-B" is negative. In contrast, when the signal "X-B" is not negative the S/P conversion register adds "1" to "2S" and changes the integrated value from "S" to "2S+1". The signal "X" outputted from the multiplier is again inputted into the multiplier when the signal "X-B" is negative.

Abstract: An image obtained by imaging an object having a solid shape, such as that of a circular column or prism, develops a distribution in brightness since the angle of each portion of the surface of the object with respect to a lighting device and image pick-up device differs depending upon the location. The distribution of brightness is substantially uniform along the longitudinal direction of the object but varies transversely of the object. One line is designated on the captured image of the object in a direction that cuts across the object, and the distribution of brightness on this line is obtained. A two-dimensional shading pattern is obtained by expanding this brightness distribution in the longitudinal direction of the object. The shading pattern represents the distribution of the brightness in the image of the surface of the object.

Abstract: A charge transfer device including a charge input portion for inputting a reference charge, a charge transfer portion for receiving and transferring the reference charge, and a conversion portion converting the reference charge outputted from the charge transfer portion into a reference voltage. The reference charge input portion may be arranged to generate a reference charge. Alternatively, the reference charge may be externally generated. The charge transfer device may further include a signal charge input portion for inputting signal charges to the charge transfer portion. The signal charge input portion may be arranged to generate signal charges corresponding to incident light. Signal charges externally generated may be inputted to the signal charge input portion. The charge transfer device enables a charge-output voltage characteristic to be accurately detected at all times without any problem. It is also possible to accurately control the charge-output voltage characteristic.

Abstract: An image reading apparatus for reading an image on film which uses a shading correction coefficient computation unit for obtaining a shading correction coefficient in order to correct irregularities in image signals of a photoelectric conversion unit, and a quantity of light ratio measurement unit for obtaining the ratio of the quantity of light of each emission color in order to equalize the quantity of light emitted by a light emission unit. The shading correction coefficient and the quantity of light ratio are obtained immediately before reading of a first original medium, and additional original mediums can then be read using the correction coefficients obtained for the first original. Alternately, the shading correction coefficient and the quantity of light ratio can be obtained immediately before reading each original medium.

Abstract: A high frame rate camera includes;a multi-channel sensor array for producing a plurality of parallel analog image signals representative of a sensed image;a plurality of analog-to-digital converters (ADC) for converting each of the parallel analog image signals to parallel digital image signals, wherein each of the ADCs has a fine gain parameter which is a function of a top ladder potential and also has a fine offset parameter which is a function of a bottom ladder potential; anda control for controlling the fine gain and offset parameters of each of the ADCs by means of fine gain and offset control signals which are a function of desired average output black and gray levels of the image signal.

Abstract: A technique is disclosed for correcting black shading errors in a video camera. The technique involves calculating a horizontal correction waveform as a function of the average pixel values for the columns of a field. Next, a vertical correction waveform is calculated as a function of the average pixel values for the rows of a field. Then, calculation of a diagonal correction waveform as a function of the average pixel values along predetermined diagonals is performed. Finally, an input video signal representing real images is combined with the correction waveforms to produce a video output signal having substantially reduced black shading errors. Correction waveforms can be determined in any order.

Abstract: A video camera generates an approximation of the dark current or black shading distortion signals based on scan position in the image, and subtracts the approximation signal from the signal generated by the camera during normal image-sensing operation to reduce the black shading distortion. In a particular embodiment of the invention, counters generate location signals representative of the location of pixel currently being read, and the location signals are processed by functions such as squaring or raising to a constant power, and by weighting, to produce components of the approximation of the dark signal. The components are subtracted from the imager signal, to reduce the dark shading. In one embodiment of the invention, the functions are automatically selected from among a plurality of preselected functions, and implemented by look-up tables.