Abstract: An image coding method includes: performing context arithmetic coding to consecutively code (i) first information indicating whether or not to perform sample adaptive offset (SAO) processing for a first region of an image and (ii) second information indicating whether or not to use, in the SAO processing for the first region, information on SAO processing for a region other than the first region, the context arithmetic coding being arithmetic coding using a variable probability, the SAO processing being offset processing on a pixel value; and performing bypass arithmetic coding to code other information which is information on the SAO processing for the first region and different from the first information or the second information, after the first information and the second information are coded, the bypass arithmetic coding being arithmetic coding using a fixed probability.

Abstract: The present application discloses a driving method and a driver chip for a display panel, and a display device, where the driving method includes steps of: acquiring a refresh rate of a first data information; performing local dimming on the first data information to generate a first backlight driving information and a first data driving information; and adjusting the first backlight driving information and the first data driving information according to the refresh rate to generate a second backlight driving information and a second data driving information, respectively.

Abstract: Disclosed herein are methods, systems, and computer-readable storage media for generating three-dimensional (3D) images of a scene. According to an aspect, a method includes capturing a real-time image and a first still image of a scene. Further, the method includes displaying the real-time image of the scene on a display. The method also includes determining one or more properties of the captured images. The method also includes calculating an offset in a real-time display of the scene to indicate a target camera positional offset with respect to the first still image. Further, the method includes determining that a capture device is in a position of the target camera positional offset. The method also includes capturing a second still image. Further, the method includes correcting the captured first and second still images. The method also includes generating the three-dimensional image based on the corrected first and second still images.

Abstract: A tone-mapping technique based on bidirectional logarithm stretch enhances the luminance contrast of not only the dark areas but also the bright areas. In other words, the algorithm not only maps the dark pixels brighter but also map the bright pixels darker.

Abstract: An image coding method includes: performing context arithmetic coding to consecutively code (i) first information indicating whether or not to perform sample adaptive offset (SAO) processing for a first region of an image and (ii) second information indicating whether or not to use, in the SAO processing for the first region, information on SAO processing for a region other than the first region, the context arithmetic coding being arithmetic coding using a variable probability, the SAO processing being offset processing on a pixel value; and performing bypass arithmetic coding to code other information which is information on the SAO processing for the first region and different from the first information or the second information, after the first information and the second information are coded, the bypass arithmetic coding being arithmetic coding using a fixed probability.

Abstract: The invention relates to a method for investigating signal parameters in an electrical measuring device with a display element with the method steps: display of a detected signal on the display element, manual masking of at least one signal component of the signal by a user by means of a masking element of the measuring device and investigation of signal parameters from the masked signal component or from the unmasked signal component of the signal by the measuring device. At least one further signal parameter is also investigated alongside the time duration and the bandwidth of the masked signal component. According to the invention, a corresponding measuring device is also provided.

Abstract: An apparatus is described that includes first and second pixels arrays integrated on a same semiconductor chip. The first pixel array contains visible light pixels and no Z pixels. The second pixel array contains Z pixels and no visible light pixels. The first and second pixel arrays do not overlap on said same semiconductor chip.

Abstract: An apparatus is described that includes first and second pixels arrays integrated on a same semiconductor chip. The first pixel array contains visible light pixels and no Z pixels. The second pixel array contains Z pixels and no visible light pixels. The first and second pixel arrays do not overlap on said same semiconductor chip.

Abstract: An image coding method includes: performing context arithmetic coding to consecutively code (i) first information indicating whether or not to perform sample adaptive offset (SAO) processing for a first region of an image and (ii) second information indicating whether or not to use, in the SAO processing for the first region, information on SAO processing for a region other than the first region, the context arithmetic coding being arithmetic coding using a variable probability, the SAO processing being offset processing on a pixel value; and performing bypass arithmetic coding to code other information which is information on the SAO processing for the first region and different from the first information or the second information, after the first information and the second information are coded, the bypass arithmetic coding being arithmetic coding using a fixed probability.

Abstract: An image coding method includes performing: context arithmetic coding to consecutively code (i) first information indicating whether or not to perform SAO processing for a first region and (ii) second information indicating whether or not to use, in the SAO processing for the first region, information on SAO processing for a region except the first region; and bypass arithmetic coding to code other information after the first and second information are coded. The other information includes third information indicating whether the SAO processing is edge or band offset processing. In the performing of context arithmetic coding, an initial bit value in a bit string of a parameter indicating a type of the SAO processing is coded as the first information. In the performing of bypass arithmetic coding, a value of a next bit following the initial bit in the bit string of the parameter is coded as the third information.

Abstract: A video processing method and an apparatus using the same are disclosed. The method includes steps of performing a brightness-reducing treatment on all pixels in a displayed image; performing a brightness-enhancing treatment on all first pixels in the displayed image; performing a brightness-smoothing treatment on pixels having a brightness value being between a higher smooth-treatment brightness value and a lower smooth-treatment brightness value. The video processing method keeps the brightness value of the pixels from being out of grayscale range.

Abstract: A signal processing unit; includes: a high-frequency signal determination section configured to determine whether a reference region as a peripheral region of a phase difference pixel is a high-frequency signal region in a specific direction based on a pixel signal output from an image pickup section having the phase difference pixel disposed therein; and a synthetic ratio determination section configured to, when the reference region is determined to be not the high-frequency signal region in the specific direction, determine, using a pixel difference of the reference region, a synthetic ratio of an interpolated value of the phase difference pixel by a gain multiple interpolation technique to an interpolated value of the phase difference pixel by a peripheral pixel interpolation technique.

Abstract: A video processing system may be operable to utilize multi-band sharpening to process luma signals for image signals. The luma signal may be decomposed into a plurality of frequency band components, wherein each component may be processed separately using different sharpening gains and/or offsets. The multi-band processed components may be combined to generate sharpened output luma signals. The multi-band sharpening may be performed utilizing peaking processing, and the input luma signal and/or LTI sharpened luma signals may be combined with the multi-band peaking sharpened signals to generate the sharpened output luma signals. Corresponding chroma signals may also be adjusted to generate sharpened output chroma signals. Luma and/or chroma sharpening operations may be further adjusted based on coring, clipping avoidance, luma statistics, color region detections, and/or curve control parameters.

Abstract: An image processing apparatus includes a unit configured to calculate a plurality of characteristic amounts from an input image, a unit configured to calculate a first multidimensional lookup table based on the characteristic amounts, a unit configured to calculate attribute information of a specific object from the input image, a unit configured to calculate a second multidimensional lookup table based on the attribute information, a unit configured to generate a control parameter from the input image, an interpolation unit configured to apply the first and second multidimensional lookup tables to the input image, and a control unit configured to control interpolation intensity of the second multidimensional lookup table using the control parameter.

Abstract: A device includes converters for converting first image data of an RGB-type into second image data of a YCbCr-type, into third image data of the YCbCr-type, and into fourth image data of the RGB-type, wherein a CbCr-coordinate system has six regions defined by coordinates of a reference color and of six primary colors, and when coordinates of the second image data are located in a region defined by coordinates of the reference color, a first primary color, and a second primary color, the coordinates of the second image data are determined by the coordinates of the reference color, the first primary color, the second primary color, coordinates of a target reference color corresponding to those of the reference color, coordinates of a first target primary color corresponding to those of the first primary color, and coordinates of a second target primary color corresponding to those of the second primary color.

Abstract: The present invention provides a method for enhancing contrast of a color image displayed on a display system and an image processing system utilizing the same. In the present invention, the gray values of R, G, and B components of one color image are separately counted during processing the image. When calculating the corresponding output values for the gray values of R, G, and B components in each pixel, they are adapted to ratios between the gray values of R, G, and B components. Therefore, the present invention can effectively maintain the color distribution for a considerable degree and greatly enhance the image contrast.

Abstract: When a single pixel is displayed by four color sub-pixels, or R (red), G (green), B (blue), and G, in a Bayer array, this invention sets the scaling rate of a scaling process to 3/2 times when executing the scaling process on image data having three color components, or R, G, and B, and then executes a color conversion process for finding four color components from the three color components; after this, a decimation process for reducing the number of pixels is carried out. Setting the scaling rate of the scaling process to an integer proportion, moirés caused by the scaling process can be made less noticeable. Note that it is desirable for the scaling rate of the scaling process to be close to ?2 and for the denominator of the integer proportion to be lower.

Abstract: A color adjustment system for a display device includes a computer device, and a display device for displaying an image. The display device selectably displays a plurality of color temperature color presets. The computer device makes a white point adjustment to the display device, based on a color temperature color preset selected from among the plurality of color temperature color presets by a selecting operation from the computer device.

Abstract: System and methods for gamut bounded saturation adaptive color enhancement are provided. Color enhancement incorporating gamut bounded saturation enhances colors of an pixel from a source color gamut such that the resulting color is within a target color gamut. This resulting color may, for example, take advantage of an expanded target color gamut of a display. Gamut bounded saturation may be implemented independently or in combination with RGB bounded saturation.

Abstract: A method for eliminating image blur includes: detecting the difference in pixel value between two corresponding pixels in two continuous images to generate a difference value; and adjusting the luminance of the two corresponding pixels according to the difference value, wherein when the difference value exceeds a predetermined value, the luminance of one pixel of the two corresponding pixels is increased and the luminance of the other pixel is decreased.

Abstract: An apparatus and method for adjusting hue in an image processing device are provided. The method includes: setting a rotation angle of hue of each of regions of an image divided into a predetermined number about a central point; calculating coordinates of hue values Cr and Cb of an input pixel to determine in which of the regions the pixel is located; calculating an angle of the pixel in the determined region; calculating a movement angle using rotation angles set for the determined region and an adjacent region, and determining whether interpolation is to be performed to the angle of the pixel based on a difference between the movement angle and the angle of the pixel; and if it is determined that the interpolation is to be performed, calculating an interpolation angle using the movement angle and the angle of the pixel, and moving the pixel by the interpolation angle.

Abstract: An image processing apparatus for sharpening edge boundaries of an image is provided. The image processing apparatus includes a transient improvement (TI) circuit and a color protection circuit. The TI circuit receives multiple original pixel data and performs a TI process on an original target pixel data from the original pixel data to output first and second TI chroma signals corresponding to the original pixel data. The color protection circuit respectively compares the first and second TI chroma signals with first and second original chroma signals of the original pixel data to correspondingly generate a weighting value, and outputs first and second adjusted chroma signals according to the weighting value, the first and second original chroma signals, and the first and second TI chroma signals.

Abstract: A pixel interpolation process is based on detection of a potential edge in proximity to a pixel being estimated, and the angle thereof. The potential edge and its angle is determined based on filtering of offset or overlapping sets of lines from a pixel window centered around the pixel being estimated and then cross-correlating the filter results. The highest value in the correlation result values represents a potential edge in proximity to the pixel being estimated and the index of the highest value represents the angle of the potential edge. This information is used in conjunction with other information from the cross-correlation and analysis of the differences between pixels in proximity to verify the validity of the potential edge. If determined to be valid, a diagonal interpolation based on the edge and its angle is used to estimate the pixel value of the pixel. Otherwise, an alternate interpolation process, such as vertical interpolation, is used to estimate the pixel value for the pixel.

Abstract: A video signal processing apparatus includes: an enhancement gain generating section obtaining an enhancement gain for each pixel based on an luminance signal forming part of an input video signal and a predetermined enhancement gain; and an enhancing section performing a process of enhancing the luminance signal forming part of the input video signal based on the enhancement gain. The enhancement gain generating section includes a mean deviation calculating portion obtaining a mean deviation of luminance values of pixels included in a predetermined region centered at a pixel of interest that is the pixel for which the enhancement gain is to be obtained, a weighting coefficient generating portion generating a weighting coefficient for the pixel of interest according to the value of the mean deviation, and a multiplication portion multiplying the predetermined enhancement gain by the weighting coefficient to obtain the enhancement gain for the pixel of interest.

Abstract: A histogram generation portion calculates a prescribed feature value of a pixel and the maximum feature value for the pixel, for each pixel of one frame of an input video signal. Then, the ratio of the feature value of the pixel to the maximum feature value is calculated for each pixel as an index of color brightness, and a histogram generated wherein the numbers of pixels are integrated by index value. An enhancement processing portion applies gain and carries out an enhancement for pixel values wherein the index in the histogram which the histogram generation portion generates is greater than or equal to a prescribed threshold. The feature value is treated as a luminosity (L*) which is defined with CIELAB chroma space. Additionally, the feature value may be data which has the maximum tone value among pixel RGB data, or may be a luminosity value (Y) of the pixel.

Abstract: A color conversion device generates color data in a second color gamut based on first converted color data and input color data, which are obtained from input color data in a first color gamut, and outputs the color data in the second color gamut. The color conversion device includes a first color mapping unit which generates the first converted color data by mapping the input color data into the second color gamut; a color mixing unit which generates color data by mixing the first converted color data and second converted color data at a ratio corresponding to the first color gamut and the second color gamut; and a color data output unit which outputs the color data.

Abstract: System and methods for gamut bounded saturation adaptive color enhancement are provided. Color enhancement incorporating gamut bounded saturation enhances colors of an pixel from a source color gamut such that the resulting color is within a target color gamut. This resulting color may, for example, take advantage of an expanded target color gamut of a display. Gamut bounded saturation may be implemented independently or in combination with RGB bounded saturation.

Abstract: The fact that B and R are close to a U axis and to a V axis, respectively, is noted. On that basis, from an example of color adjustment parameters set in directions of colors, it is found out that, when inputted V is in a negative range, B has a small influence. Accordingly, a B component is omitted from calculation in order to reduce a calculation amount. Similarly, components having small influences are omitted when B is in a positive range, when U is in the positive range, and when U is in the negative range. Thereby, adjustment parameters AR, AG, and AB set in directions shown in the drawing can be defined. When inputted V is in the positive range, a V component can be adjusted by multiplying AR by the inputted V. Similar processing is performed when inputted V is in the negative range, when U is in the positive range, and when U is the negative range, respectively.

Abstract: The subpixel rendering component of a display system provides the capability to substitute a second subpixel rendering filter for a first subpixel rendering filter for computing the values of certain subpixels on the display panel when the input image data being rendered indicates an image feature that may give rise to a color balance error at some portion of the displayed output image. An image processing method of correcting for color balance errors detects the location of a subpixel being rendered and for certain subpixels, detects whether the input image data indicates the presence of a particular image feature. When the image feature is detected for particular subpixels being processed, a second subpixel rendering image filter is substituted for a first subpixel rendering image filter.

Abstract: A display device capable of displaying an image selected by a user for a certain period of time without interruption even when power consumption to be used to completely display the image exceeds a remaining capacity of a battery, and a method of driving the same. The display device includes a storage element; a selection circuit configured to select an image stored in the storage element according to a user request; a battery; a first detection circuit configured to detect a remaining capacity of the battery; a controller; and a display panel coupled to the battery via the controller and configured to display the selected image in accordance with a control output of the controller.

Abstract: An image processing method and its associated image processing circuit for processing an image based on a sequential couleur avec memoire (SECAM) system are provided. The image includes a first pixel, a second pixel and a third pixel, which are successively arranged in a same vertical line and are respectively corresponding to a first image signal and a second image signal and a third image signal. The image processing method includes steps of calculating a chroma signal via a vertical filtering process according to the first image signal, the second image signal and the third image signal; calculating a chroma angular frequency via a frequency modulation process according to the chroma signal; and generating a chromaticity according to the chroma angular frequency.

Abstract: A device for outputting a luminance signal and a method thereof are disclosed. The device includes an image smoothing unit, a band pass filter unit, and a summing unit. The image smoothing unit receives a 2D luminance signal and decreases a signal intensity of a component of the 2D luminance signal within a frequency range with respect to a carrier frequency of a chrominance component. The band pass filter unit passes the component of the 2D luminance signal within the frequency range with respect to the carrier frequency. The summing unit sums the output of the image smoothing unit and the output of the band pass filter unit to generate a resultant luminance signal. The present invention is capable of avoiding the occurrence of saw-tooth or sparkling situation caused by inharmonious switching between a 1D comb filter and a 2D comb filter.

Abstract: A method and system are described for adjusting displaying of images to be displayed on a display system. The method is suitable for display systems comprising at least one hardware feature (f1, f2, f3) influencing the display uniformity of the displaying of images, such as e.g. a defect pixel, seams, variations in positions of hardware components, etc. The method comprises obtaining pixelated image information to be displayed on a display system (100), and adjusting the displaying thereof by applying a distributed variation correction signal to the displaying of the pixelated image information. Such a distributed variation correction signal thereby takes into account the at least one hardware feature (f1, f2, f3) of said display system (100) so as to influence the perception of the display uniformity.

Abstract: A computerized device for converting a color image data, indicative of a plurality of color image regions defining a two-dimensional color image, into a grayscale image data indicative of a plurality of grayscale image regions defining a two-dimensional grayscale image, with each of the color image regions corresponding to one of the grayscale image regions. A luminance information and a two-dimensional chromatic information is associated with each of the color image regions. The device includes a processor and a memory store. The memory store is adapted to store a program executable by the processor so as to perform the following steps: determining a principal chromatic component of each of the color image regions; determining a first correlation value; and generating the grayscale image data by reference to the first correlation value.

Abstract: A parameter for determining a chrominance correction curve for use in correcting the chrominance component of each pixel is determined from one or more parameters for determining a luminance correction curve for use in correcting luminance applied to the entirety of one frame of motion picture data. The chrominance component of each pixel is corrected using the chrominance correction curve.

Abstract: A circuit and a method for image processing are provided. The image processing circuit has an adaptor and a sharpening circuit. The adaptor has a processing unit and a weight generator. The processing unit receives an input video signal, and the input video signal has information of a plurality of pixels. The processing unit processes the input video signal to calculate a color difference value of a target pixel of the pixels. The weight generator generates a weighting signal according to the color difference value. The sharpening circuit performs a sharpening operation on the input video signal according to the weighting signal to generate a sharpened video signal.

Abstract: The adaptive contrast enhancer uses an adaptive histogram equalization-based approach to improve contrast in a video signal. For each video frame, the histogram of the pixel luminance values is calculated. The calculated histogram is divided into three regions that are equalized independently of the other. The equalized values are averaged with the original pixel values with a weighting factor that depends on the shape of the histogram. The weighting factors can be also chosen differently for the three regions to enhance the darker regions more than the brighter ones. The statistics calculated from one frame are used to enhance the next frame such that frame buffers are not required. Many of the calculations are done in the inactive time between two frames.

Abstract: A display method and apparatus are provided for enabling a user, whether or not he has experience, to readily detect a luminance level of a video image with high accuracy. A luminance level of a video signal of a video image is converted to color information to display a change in the luminance of the video image as a change in color. The conversion preferably involves a method of converting the luminance level to color information of three primary colors, red, green, blue, in accordance with a plurality of weights, respectively, a method of converting a luminance level in a predetermined range to color information having a changing rate larger than a changing rate of the luminance level, a method of converting a luminance level out of the predetermined range to color information of a maximum or a minimum level, or the like. Also, the input video signal is preferably displayed together with a converted video image side by side or one on another.

Abstract: A system of edge direction detection for comb filter includes a buffer, first and second filters, first and second oblique detectors, and a comparator. The buffer receives and stores a composite signal. The first filter performs filtering operation on the composite signal to produce a first filter signal. The second filter performs filtering operation on the composite signal to produce a second filter signal. The first oblique detector detects an oblique in the first filter signal to produce a first oblique indication signal and a first oblique direction signal and output a first minimum oblique difference. The second oblique detector detects an oblique in the second filter signal to produce a second oblique indication signal and a second oblique direction signal and output a second minimum oblique difference. The comparator compares the first and second oblique indication signals and the first and second oblique direction signals to produce edge information.

Abstract: A system (600) for performing gamut compression or gamut extension by transforming an input color (608) of an input image defined within a first gamut (102) into a reproduction color (610) of an output image for rendering by a reproduction device capable of rendering colors within a second gamut (104) different from the first gamut. The input color has an input chromaticity (C1) and an input lightness (Z-*) together forming an input point (202) in a chromaticity-lightness plane. The reproduction color has a reproduction point (210) in the chromaticity-lightness plane, wherein an absolute difference between the input lightness and the output lightness is a decreasing function of at least the chromaticity. An absolute difference between the input chromaticity and the output chromaticity is an increasing function of at least the chromaticity.

Abstract: The present invention relates to a method and corresponding system for improving the perceived visual quality of images for instance displayed on a color television screen. According to the invention, there is provided a means for carrying out histogram processing (13) for scaling an input video signal (6) such that the maximum dynamic range is utilised and where the quality of the perceived image is also optimised. According to the invention, the histogram processing (13) provides a transfer function for the image pixels to obtain enhanced image dynamics and also to provide a chrominance gain (gc) for scaling the chrominance components, when the luminance has been changed by the histogram processing. According to the invention, the histogram processing can also take variations of the ambient light into account (5).

Abstract: A method presents metadata that is used for determining the color correction processes to be performed on image data representing a sequence of moving images. Instructions in the metadata controls how many color corrections are to be performed and when such operations occur. The image data is then subjected to the specified color correction operations that are performed at specified times and in a determined order. The image data is then rendered as a series of images by a rendering device. Optionally, different regions of the image data may be subjected to different color correction operations.

Abstract: An image enhancement unit and method for enhancing the image quality of a video stream is presented. The image enhancement unit combines a contour enhancement unit, a luminance contrast stretching unit, a color transient improvement unit, and a color saturation control unit to enhance both the luminance and chrominance values in the video stream. Specifically, the contour enhancement unit processes the luminance values to improve the contours of the images in the video steam. The luminance contrast stretching unit further improves the luminance by enhancing the contrast in the images. The color transient improvement unit processes the chrominance values to remove blurring around along the edges of color transitions and the color saturation control unit increases the color saturation to improve the appearance of the images.

Abstract: A dynamic motion degree of a video composite signal is estimated. A chrominance signal after Y/C separation and chrominance demodulation is narrow-band low pass filtered (NBLPF) and wide-band low pass filtered (WBLPF), so as to generate a narrow-band filtered signal and a wide-band filtered signal. The narrow-band filtered signal and the wide-band filtered signal are weighted based on the estimated dynamic motion degree, so as to determine how much high frequency component of the chrominance signal is reserved. In the static image processing, more high frequency component is reserved, so as to reduce the color transition issue and keep the image color being sharp. In the dynamic image processing, more high frequency component is filtered, so as to reduce the cross color issue.

Abstract: An image processing method and an image processing apparatus are provided. After receiving an image signal, the image and apparatus according to the invention first judge whether a target block in the image signal includes a non-chroma line. If the judging result is YES, a first edge detection procedure will be performed on the non-chroma line. If the judging result is NO, a second edge detection procedure will be performed on the target block.

Abstract: In an image processing apparatus, a first conversion unit converts, on the basis of an input device profile, input data into first device-independent data expressed by a color space that is independent of an apparatus. A storage unit stores plural conversion profiles for converting using a color appearance model in the color space that is independent of the apparatus in correspondence with plural device characteristics that are dependent on apparatuses. A selection unit selects a conversion profile corresponding to characteristics of the input device, characteristics of an output device, observation conditions of the input data and the output data. A second conversion unit converts, on basis of the selected conversion profile, the first device-independent data into second device-independent data. A third conversion unit converts the second device-independent data into the output data on the basis of an output device profile.

Abstract: An image signal is resolved into a plurality of frequency components whose spatial frequencies are different from each other; a variation component of the image signal is extracted based on each of the plurality of frequency components, an absolute value of the variation component being smaller than a predetermined reference value; a level difference amount of the image signal is calculated based on the extracted variation component; and the calculated level difference amount is subtracted from the image signal.

Abstract: An image correction circuit capable of easily achieving adaptive color correction on the basis of a luminance correction amount is provided. An image correction circuit includes: a luminance correction section for performing luminance correction on input image data; and a color correction section for performing adaptive color correction on input image data on the basis of the following formula (1): Cout?Cin×[1+M×(?Y/L)]??(1) where Cout represents a chrominance signal after color correction, Cin represents a chrominance signal before color correction, M represents an adaptive color correction magnitude which is a fixed positive value, ?Y represents the total amount of luminance correction by the luminance correction section, L represents a fixed positive value satisfying L<(Ymax/2), and Ymax represents maximum luminance of input image data.

Abstract: White balancing is performed using a mapping that maps the visible gamut's boundary into itself. A predefined color Win is mapped into a color Wout which is a white color or a color perceived as white under some viewing conditions. If Sin is some other color, a corresponding color Pin is determined on the visible gamut's boundary. Pin can be on the intersection of the visible gamut's boundary with a plane containing Sin and Win in a linear color coordinate system. Sin is mapped into a color Sout obtained from Wout and a value of the mapping on Pin.

Abstract: The invention discloses an image processing apparatus for adjusting the lightness of an input image which has a hue. The image processing apparatus includes a look-up table, a processing unit and an adder. The look-up table records M lightness, N hues and M*N corresponding lightness offset values. The processing unit is used for storing the look-up table and for selecting a corresponding lightness offset value from the look-up table according to the lightness and the hue of the input image. The adder is coupled to the processing unit and used for adding the selected lightness offset value to the lightness of the input image, so as to obtain an adjusted lightness. Accordingly, the image quality is improved.