Abstract: A method for improvement of contrast in an image shown on a display having a range of displayable video levels. The method comprises providing input video levels representing the image, said levels being within said displayable range; providing a transfer function (120, 121) having a slope greater than one everywhere in a gain region (130) of said displayable range, and a slope greater than zero and less than one everywhere in a softclip region (131) of said displayable range, said regions (130, 131) meeting at a threshold level (125), the transfer function (120, 121) being adapted to transfer any input video level within said displayable range to an output level within displayable said range; and transforming said input levels into output levels within said range, using the transfer function (120, 121). According to the invention, instead of “hardclipping” there is a “softclipping” of levels. Hence, compared to conventional methods, a higher gain may be used.

Abstract: An image processing device extracting a contrast component for each pixel of an input image by removing a low-frequency component of the input image and correcting the contrast component for each pixel based on a gain value, including: an input/output-property generating unit for generating an input/output-property curve, assuming an input contrast component which is the pre-correction contrast component as input, and an output contrast component which is the post-correction contrast component as output, which is an input/output-property curve of which the output contrast component monotonously increases as to the input contrast component; a gain properties generating unit for generating a gain property curve representing properties as to the input contrast component of the gain value for correcting the input contrast component to obtain the output contrast component based on the input/output-property curve; and a gain-value calculating unit for calculating the gain value for each pixel of the input image bas

Abstract: An image processing method aims to optimally improve a brightness distribution with respect to brightness of a face being a main subject of a person image. Thus, the method consists of: a brightness component extraction step of extracting a brightness component from image data; a low-frequency brightness component extraction step of extracting a low-frequency component signal of the brightness component as a low-frequency brightness component; a color adjustment step of performing color adjustment to the image data by using the brightness component and the low-frequency brightness component; a first parameter determination step of determining a first parameter; and a second parameter determination step of determining a second parameter in accordance with a distribution of brightness component values in a second area in the image data, wherein the color adjustment step causes processing a degree of the color adjustment according to the first and second parameters.

Abstract: An electro emission device (EED) operated by a driver for modulating the pulse width of a driving pulse according to a pulse width modulation (PWM) clock signal to control the brightness of images. The EED calculates a brightness level of image data indicating the brightness of the whole image for each unit image of a video signal. The image data is stored for each unit image of the video signal. The reference brightness level stored in the look-up table is compared with a calculated brightness level to determine a signal of the PWM clock signal condition. A PWM clock signal is generated according to the signal of the PWM clock signal condition to drive the display panel based on the PWM clock signal.

Abstract: To automatically adjust the quality of a projection image commensurate with the performance in-time deterioration and aging of projector component parts in an image projection system, each projector detects an integrated service time of its own light-source lamp and a service time and temperature of a liquid-crystal panel, and sends a detection result thereof to a control unit in compliance with a request from the control unit. These parameter values are parameter values having an effect upon the quality of a projection image and varying with time. The control unit copes with the projectors depending upon the detection result received from the projectors, to set predetermined control data for use in image-quality adjustment and send the control data respectively to the projectors. Each projector controls the driving to its light-source lamp and liquid-crystal panel, depending upon the control data received from the control unit.

Abstract: In image processing apparatus and method for displaying and printing a person image photographed by a digital camera, it is possible to automatically correct image data and output the person image of an optimum characteristic. In this apparatus, an image obtaining processor obtains the image data from a recording medium, a face region extraction processor extracts a face region of a person from the obtained image data, an image feature amount calculator calculates an image feature amount of the extracted face region, a correction effect inference processor infers whether or not a correction effect can be obtained by correcting a characteristic of the image data, based on the calculated image feature amount, and an image correction processor corrects the characteristic of the image data based on the image feature amount and thus outputs post-correction image data when it is inferred that the correction effect can be obtained.

Abstract: An image brightness and contrast management module for automatically adjusting brightness and contrast of an input video signal includes a histogram generation unit that generates a pixel luminance histogram based on pixel luminance values in a frame, whereby the histogram shows a distribution of luminance values in the frame and indicates the dynamic range and the dominant luminance value(s) for the frame. The module includes a histogram characterization unit that uses the pixel luminance histogram to identify which of a plurality of brightness/contrast properties is exhibited in the frame. The module also includes a brightness and contrast adjustment unit that nonlinearly adjusts, in real-time, the pixel luminance values in a next frame based on the identified brightness/contrast properties exhibited in the preceding frame.

Abstract: A contrast control apparatus includes a memory for storing input image signals within one frame and an image reducing unit for selecting at least one image signal of the input image signals. An accumulation value calculating unit calculates accumulation values for predetermined sampling gray values with respect to the selected image signal. An image characteristic decision unit determines at least one characteristic of the selected image based on the accumulation values. A contrast control function calculating unit calculates a contrast control function based on the characteristic of the selected image. A contrast controller controls contrast of the image signals stored in the memory according to the contrast control function.

Abstract: A gamut error false color display uses false coloring on a monochrome image of a video picture being tested. Composite and component gamut error signals are extracted from an input video signal representing the video picture being tested. Such error signals may represent gamut error states corresponding to near out-of-gamut, out-of-gamut high, near out-of-gamut low, out-of-gamut low, etc. A false color display generator has the gamut error signals and a luminance component of the input video signal as inputs and outputs the gamut false color display as the monochrome image with different colors for those pixels in the monochrome image that correspond to the gamut error signals when a gamut error is indicated. Each display component may be tested for gamut errors as well as the video picture as a whole (component or composite). Also either fixed or variable persistence may be used to identify gamut errors over several video pictures in the input video signal.

Abstract: An automatic contrast limiting circuit and method thereof with spatial domain infinite impulse response filter are disclosed. A spatial domain infinite impulse response filter is adapted to generate an output value of the spatial domain infinite impulse response filter related to an input signal. A peak value detector is adapted to detect the peak output value of the spatial domain infinite impulse response filter during a predetermined recording interval. A contrast evaluator is used to evaluate the required contrast value referring to a predetermined threshold value and the output value of the spatial domain infinite impulse response filter.

Abstract: A device for producing a video image sharpness improvement signal (DOC21-DOC22), with black level clipping of an associated video signal, comprises a differential transconductance stage processing the video signal and whose bias currents (Imax) are directly proportional to the active component (?V) of the video signal so as to bring about a black level sharpness improvement signal clipping.

Abstract: An apparatus for and a method of continuously adjusting a brightness and a contrast of a video display. An analog video signal is converted to provide digital luminance (Y) signals and amplitudes of the digital Y signals are adjusted based on determining whether the digital Y signals of a frame have amplitudes corresponding to one or more of four regions of digital values. The four regions include a highest region, a second highest region, a lowest region and a second lowest region. Contrast is adjusted based on whether digital Y values of the frame are included for the highest region and/or the second highest region and brightness is adjusted based on whether digital Y values are included for the lowest region and/or the second lowest region.

Abstract: Digital dc restore methods and apparatus to restore the DC component of an analog waveform to a quantized reference value level at a given temporal point on a waveform, prior to an ADC. This may used to establish the relationship between the full scale digital value out of the ADC and the waveform being digitized. For a video signal, the Digital Value of Black, is compared with the value on the back porch of the video signal. The difference is converted to the analog domain by a DAC clocked at the Temporal Point to provide a sample and hold function. An amplifier compares the difference, mapped to one half full scale digital, to an analog common mode voltage for the ADC, removing any error due to the difference between them. Other applications include correlated double sampling of contact image sensors to remove Dark Current Offset.

Abstract: A video output device adds a blank on both left and right sides or both upper and lower sides of an input video to produce a video having the same aspect ratio as that of the display screen of the display device, when an aspect ratio of the input video and an aspect ratio of a display device for displaying the video are different. At this time, the brightness of the blank to be added to the input video is adjusted in accordance with the brightness near the boundary between the input video and the blank to suppress a difference in brightness near the boundary.

Abstract: Provided is a method of automatically setting image quality, which maintains a brightness and a contrast of an image regardless of a status of an input signal. The method includes: (a) setting a variable range of brightness and a variable range of contrast; (b) converting a brightness signal included in an input video signal into a digital signal and recording the digital brightness signal in a plurality of registers according to brightness level; (c) changing a brightness value or a contrast value of an output video signal by comparing values of a first register, second register, third register, and fourth register among the registers to predetermined values; and (d) if the changed brightness value is in the variable range of the brightness and the contrast value is in the variable range of the contrast, determining that the compensation of image quality is complete, and returning to step (b).

Abstract: An apparatus, system and method for clamping a video signal input to a coupling capacitor (215) for providing a clamping voltage. A charging current is applied to the capacitor (215) via an amplifier (225) having a first input (227) coupled with the capacitor output and a second input (226) coupled to a reference potential, the amplifier (225) is responsive to the capacitor output signal and the reference potential for providing the charging current to the capacitor (215). The current has a linearly varying magnitude which is proportional to a difference between the capacitor output and the reference potential.

Abstract: A signal processing unit in a liquid crystal display device, etc., includes a brightness component appearance frequency measuring unit that measures an appearance frequency of each brightness component in a video signal; a parameter outputting unit that outputs a distribution of each brightness component, as a parameter, based on the appearance frequency of each brightness component measured by the brightness component appearance frequency measuring unit; a changing signal outputting unit that alters an input signal recorded in a recording unit, by using the parameter, and that outputs the input signal as a changing signal; and a brightness component changing unit that changes a distribution of each brightness component, by using the changing signal, and that outputs the video signal in which the distribution of each brightness component is changed.

Abstract: Digital circuitry for imparting halftone to that portion of a video image over which an on-screen-display (OSD) window is superimposed.

Abstract: A gray scale bistable electro-optic display is driven by storing a look-up table containing data representing the impulses necessary for transitions, storing data representing at least an initial state of each pixel of the display, storing data representing temporal and gray level prior states of each pixel, receiving an input signal representing a desired final state of at least one pixel of the display; and generating an output signal representing the impulse necessary for a transition, as determined from the look-up table, dependent upon the temporal and gray level prior states. Other similar methods for driving such displays are also disclosed.

Abstract: A method for dynamically adjusting video brightness performs histogram equalization on a video YUV brightness/color signal to generate an equalization brightness curve. The brightness of each pixel is compared with every pixel of the video frame before and after histogram equalization to generate a comparison difference value. The brightness of the pixel is adjusted so that the brightness difference after adjustment won't be larger than three times of the comparison difference value and won't be smaller than a fourth of the comparison difference value. The brightness of each pixel before and after histogram equalization is compared, one by one, to generate a brightness difference value. The brightness difference value is adjusted so that the brightness difference after adjustment won't be larger than a largest brightness value and won't be smaller than a smallest brightness value. The brightness of each video frame can be properly adjusted to accomplish clearer displaying effect.

Abstract: A method and apparatus for controlling the brightness of an image processing device to improve a brightness characteristic of an image signal, by reducing a pedestal voltage range and correspondingly expanding a brightness control voltage range in a highlight mode. The brightness control method includes the operations of determining whether a highlight mode is enabled; and if the highlight mode is enabled, reducing a pedestal voltage range by a first predetermined value and expanding a brightness control voltage range by a second predetermined value. The pedestal driving voltage and the brightness control voltage can be reciprocally controlled without modifications to a circuit having limited amplification, and the brightness can be improved without saturating an image in a highlight mode.

Abstract: A method and apparatus for selectively enhancing contrast depending on the level of incoming video signals while preserving colors are provided. An apparatus for enhancing the contrast and brightness of a video signal displayed on a display device includes: a first luminance level transformation circuit that receives luminance and chrominance signals, reduces the level of the luminance signal in response to a first control signal, and outputs the chrominance signals and the luminance signal whose level has been reduced; an image converting circuit that receives the output signals from the first luminance level transformation circuit and converts the received signals into RGB video signals; and a second luminance level transformation circuit that receives the RGB video signals from the image converting circuit, concurrently increases the respective levels of the RGB video signals in response to a second control signal, and outputs the RGB video signals whose levels have been increased.

Abstract: The present invention relates to controlling contrast in at least part of a picture. The contrast control is performed by reducing the saturation (2–4) of the picture during contrast increase (1).

Abstract: At first, average brightness of each of frames of a moving image is calculated by a computer. Following that, a moving average along a time axis is calculated for each of the frames so that moving average brightness is generated as a reference data of brightness. Next, difference data between the average brightness and the moving average brightness are generated. Further, the difference data are grouped based on the signs of the reference data. Then, on the basis of the grouped difference data, it is judged whether an unwanted change of brightness is present. Thus, it is automatically and precisely judged whether the unwanted change of brightness such as a flicker is present in the moving image.

Abstract: An average luminance calculation section 7 calculating an average luminance of video data to output an average luminance level, latches 8 to 10 delaying said average luminance levels by one-frame portion respectively to output them, a LUT 2 outputting a pre-set maximum correction factor e when the video data is input, correction factor calculation sections 3 to 6, adders 11 and 12, and a multiplier 12 are provided, each of the correction factor calculation sections compares the corresponding average luminance level out of the average luminance levels, which were output, with a plurality of correction thresholds respectively to carry out weighting of the maximum correction factor e responding to the comparison result and to output it as each correction factor, and simultaneously the adders 11 and 11, and the multiplier 12 correct the luminance level of the video data based on the average value of these correction factors.

Abstract: A light quantity control by a user can be synchronized to an automatic light quantity control depending on a luminance level of an input video signal.

Abstract: A method and an apparatus for changing the brightness of an image are provided. The method for changing the brightness of an image includes obtaining a level incremental rate, which denotes the degree to which the brightness of three input color components, i.e., first, second and third color components, will be increased according to a determined color gamut, scaling the input color components using the level incremental rate and determining the results of the scaling as incremental values of the input color components, obtaining a fourth color component value using the incremental values, and obtaining output color components, the brightnesses of which are increased from those of the input color components, using the fourth color component value and the incremental values.

Abstract: In a moving picture decoding display apparatus and moving picture decoding display method according to the present invention, moving picture decoder 101 decodes a moving picture signal, RGB matrix manipulation section 103 converts the decoded video signal in YCbCr format into a video signal in RGB format, contrast/brightness adjusting section 104 adjusts the contrast and brightness of the video signal in RGB format, and liquid crystal display module section 110 displays the adjusted video signal on liquid crystal panel 109. At this point, operation control section 105 switches on and off the operation of RGB matrix manipulation section 103 and contrast/brightness adjusting section 104 corresponding to the actual frame rate in moving picture decoder 101, and only when the operation is “on”, the section 105 controls so that the video signal from contrast/brightness adjusting section 104 is stored in video RAM 107 in liquid crystal display module section 110.

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 programmable gain amplifier having three separately programmable amplifiers. A programmable transconductance amplifier is followed by a programmable transimpedance amplifier, then a programmable switched capacitor amplifier. In one embodiment, this programmable gain amplifier is implemented in an analog front-end (AFE) circuit. One AFE embodiment provides a coarse pre-gain offset a black reference level sampler, and a fine post-gain offset in the programmable switched capacitor amplifier. In one embodiment, an ADC reference is sampled, and is subtracted directly from the video signal in the switched capacitor amplifier so that the zero level of the video signal is made to correspond to the zero level of the ADC.

Abstract: A video display interface controller for a host video display unit in which control signals multiplexed with component video signals are extracted and routed according to included address information. Control data associated with one or more local addresses is used for initial processing of the component video signals while control data associated with one or more remote addresses is used for subsequent signal processing.

Abstract: A video signal enhancement unit (100) and an image display apparatus containing the unit have a processing unit (102) for contrast modification of the video signal. The processing unit (102) receives input data from a contrast counter (112), designed to store a contrast count. The contrast count is decreased by a pixel counter (104) each time the total number of pixels which have video signal levels that are higher than a predetermined video level, exceeds a predefined threshold. The contrast count is increased each time a trigger means (114) generates a pulse. A contrast comparator (116) can be coupled to the contrast counter (112) to limit the contrast count to a maximum contrast value.

Abstract: It is intended to provided an image processing method, an image display unit, and a storage medium, capable of effecting an appropriate color reproduction even under a change in brightness of external illumination. In an image display unit according to the present invention wherein a desired image processing is applied to inputted image data, an tone reproduction characteristic in a dark surround of the image display unit in a dark surround and an tone reproduction characteristic in a illuminated surround of the image display unit under illumination of a predetermined luminance value are measured by a measuring means and the tone reproduction characteristic in an illuminated surround is approximated to the tone reproduction characteristic in a dark surround in a desired input tone range by a characteristic approximating means.

Abstract: A multiplexed video signal interface in accordance with the present invention provides a multiplexed component video signal which includes component video signals with OSD data and user-controllable contrast and video gain, along with the ability to individually control such signal components. This advantageously minimizes the complexity of the necessary signal interfaces and allows for greater integration of circuit functions, thereby significantly reducing circuit complexity, size and costs. Also provided is a signal peaking circuit in the form of a variable high pass filter that enhances the magnitudes of the higher frequency signal components of the component video signals and OSD data, thereby providing for sharper edges on the displayed images.

Abstract: Digital circuitry for imparting halftone to that portion of a video image over which an on-screen-display (OSD) window is superimposed.

Abstract: A CRT display device includes an on-screen display circuit for producing a display signal displayed on-screen on a CRT and superposing said produced display signal on a video signal; a brightness restraining circuit for suppressing the brightness of CRT in a range below an upper limit value based on an anode current of CRT; and a controller for controlling the operation of the on-screen display circuit and the operation of the brightness restraining circuit, and controlling a power supply to turn on or off; wherein when a display signal having a great area ratio of higher brightness portion is a discharging display signal, said controller controls said on-screen display circuit to produce the discharging display signal, upon an instruction for turning off the power supply, and controls the power supply to turn off when the operation of the brightness restraining circuit to suppress the brightness is relieved or stopped.

Abstract: An automatic beam limiter circuit (ABL circuit) calculating an average of a video signal at least a portion of the video signal is provided. After a converter circuit converts an analog signal, which is generated from the video signal, to a digital signal, a horizontal and a vertical average circuits calculate a horizontal and vertical averages of the digital signal at least a portion of the digital signal. The portion of the digital signal is a scanned line of the digital signal on a CRT. A comparison circuit compares a first calculation value calculated between a reference value and the vertical average with a second calculation value calculated between the reference value and the horizontal average, and outputs a first comparison signal and a second comparison signal based on the comparison results. A gain control circuit produces a gain control signal for adjusting the brightness/contrast in response to the first comparison and second comparison signals.

Abstract: An apparatus for and a method of continuously adjusting a brightness and a contrast of a video display. An analog video signal is converted to provide digital luminance (Y) signals and amplitudes of the digital Y signals are adjusted based on determining whether the digital Y signals of a frame have amplitudes corresponding to one or more of four regions of digital values. The four regions include a highest region, a second highest region, a lowest region and a second lowest region. Contrast is adjusted based on whether digital Y values of the frame are included for the highest region and/or the second highest region and brightness is adjusted based on whether digital Y values are included for the lowest region and/or the second lowest region.

Abstract: The circuit takes into account whether the image on a screen is too bright, whether more than one specific number of pixels have a luminance value that is greater than a given peak value and whether this condition is met in more than one specific number of lines in a picture and in more than one specific number of successive images with one such number of lines.

Abstract: A method and apparatus for adjusting the amplitude and DC bias of a video signal is presented, which may be performed in preparation for analog-to-digital conversion. This is accomplished by first converting a received voltage mode video signal to a current mode video signal. Similarly, a voltage mode bias control signal is converted to a current mode bias control signal. The amplitude of the current mode video signal is then adjusted to produce an amplitude adjusted video signal. Similarly, the amplitude of the current mode bias signal is adjusted to produce an amplitude adjusted bias control signal. The current mode amplitude adjusted signals are then combined to produce a biased adjusted current mode video signal. The biased adjusted current mode video signal is then converted back to a voltage mode signal, which may be provided to an analog-to-digital converter for conversion.

Abstract: Disclosed is a brightness control apparatus and method capable of adaptively compensating brightness values based on an average brightness of an image signal. The adaptive brightness control apparatus comprises a probability density function (PDF) calculation unit calculating a PDF based on a distribution of pixel values of pixels of an input image signal, a compensation value calculation unit for calculating an average value of the pixel values of the respective pixels, and calculating a function having a predetermined slope according to a range of the average brightness value, and a pixel value compensation unit for re-establishing the distribution of the pixel values based on the calculated function.

Abstract: An apparatus for displaying a digital video signal includes a shade reflection ratio calculator and a brightness compensator. The shade reflection ratio calculator calculates a shade reflection ratio r of each pixel per display clock using a linear distance function between a center pixel and a current pixel on a screen. The brightness compensator compensates brightness of each pixel by applying the shade reflection ratio value r and a brightness adjustment width Yrate to an input digital video signal. Thus, it is possible to improve picture quality of a video displayed on a screen.

Abstract: A method for independently controlling hue or saturation of individual colors in a real time digital video image, without affecting the hue or saturation of any other color in the same real time digital video image.

Abstract: A white balance adjusting apparatus includes a test signal source 13 for generating a black signal for testing and a white signal for testing, a first impedance means 1 for converting currents flowing through three drive transistors for amplifying primary color R, G, B signals into voltages, a second impedance means 5 connected in parallel with the first impedance means, a switch 6 which is selectively closed to flow a current through the second impedance means, a reference voltage source 7 for generating a first reference voltage at the time of performing the cut-off adjustment and a second reference voltage at the time of performing the drive adjustment, a comparator 8 for comparing the levels between the reference voltages of the reference voltage sources and the output voltage converted by the first or second impedance means, and a microcomputer 75 which generates a control signal for adjusting the white balance on the basis of the output signal of the comparator and adjusts the DC level and the AC level

Abstract: A circuit for regulating a signal, such as a cathode current. The circuit has an input stage for inputting a signal and for producing a sense signal based thereon. The circuit may input timing signals and have a first stage for comparing a first reference signal with the sense signal when a first timing signal indicates and for outputting a first correction signal based on the comparison. The circuit may have a second stage for comparing a second reference signal with the sense signal when a second timing signal indicates and for outputting a second correction signal based on the comparison. The circuit may further have elements for measuring a leakage signal in the input signal during a third time interval. In this embodiment, the first and second stages are further for subtracting the leakage signal from the sense signal prior to the comparisons.

Abstract: A multiplexed video signal interface in accordance with the present invention provides a multiplexed component video signal in which, in addition to the component video signals with OSD data and user-controllable contrast and video gain, includes control signal components for image brightness and CRT bias along with the ability to individually control such control signal components. This advantageously minimizes the complexity of the necessary signal interfaces and allows for greater integration of circuit functions, thereby significantly reducing circuit complexity, size and costs.

Abstract: In a period from temporal storage of a video signal to reading and displaying of the video signal, an average value 121 of the brightness levels obtained from a video signal before the video signal is stored in a storage means 3 and a predetermined target value 122 are used to perform a calculation by using a proportionality term and an integration term so that a quantity of limited electric currents is obtained. Moreover, the quantity of limited electric currents is provided with a non-response region or a hysteresis characteristic.

Abstract: An appropriate correction quantity is obtained for a video luminance signal on an individual video basis with a characteristic value, like the maximum or average value, of the luminance signal taken into account, thereby performing gray scale correction more effectively.

Abstract: A contrast control and clipping device is configured to determine a maximum range of enhancement that may be applied to each pixel for picture sharpness enhancement. This maximum range is used to limit the enhancement that is determined by the conventional convolution kernel and gain control modules. Preferably, the maximum range is independent of the determined convolution value, thereby minimizing the bandwidth requirements among the modules used for picture sharpness enhancement. The reduced bandwidth requirement allows for an efficient partitioning of tasks between hardware and software embodiments, and eases the overall system design task. In a multi-media application, the amount of data that is transferred between the processor and sub-components is substantially reduced, and the efficient partitioning facilitates parallel processing.

Abstract: An apparatus and method for stretching the black level of an image signal to minimize flicker are provided. A black level stretching apparatus includes a minimum and maximum value extraction unit, and an adaptive black level stretch unit. The minimum and maximum value extraction unit for extracting the minimum and maximum values of each field of an image signal removes impulse noise using at least one low-pass-filter. The adaptive black level stretch unit extracts a tilt point, which delimits a dark region that is stretched, calculates a first gradient, selects the first gradient or a second gradient defined by users according to the dynamic range of the input signal, and stretches the black level of the image signal using the selected gradient. Another black level stretching apparatus includes a minimum value extraction unit, a dark region average value extractor, and a black level stretch unit. The minimum value extraction unit extracts and outputs the minimum value of each field of an image signal.