Abstract: An apparatus and method for magnifying a dynamic range of an image while improving a contrast of an image are provided. A histogram calculator receives a digital image signal and calculates histograms depending on the illuminance distribution of an image. A histogram accumulator receives a histogram output by the histogram calculator, obtains an accumulative density function by integrating the input histogram up to each illuminance level and normalizes the accumulative density function, and generates an initial conversion function. A bias calculator determines a threshold value for dividing into a low illuminance level and a high illuminance level on the basis of a histogram output by the histogram calculator, and obtains a histogram compensation function for applying a negative bias to a histogram around the threshold value.

Abstract: A time shared histogram chip (80) implemented in a system for manipulating video signal data. The system includes a processor (82) for controlling system operation and for processing a video signal input into the system. The time shared histogram chip (80) accumulates video signal data in a format readable by the processor (82). The histogram chip (80) is operative to perform histogramming, video line summing and video line grabbing functions. Control means (100) is operatively connected to the processor and enables the processor (82) to selectively control the mode of operation of the histogram chip (80).

Abstract: A histogram equalization circuit includes a calculator and a mapper. The calculator calculates cumulative distribution function (CDF) values for the respective gray levels with respect to an input image corresponding to an area signal of a predetermined period. The mapper maps the input image of a predetermined period to a new gray level based on the CDF values of the respective gray levels. The present invention obtains a CDF value by selecting a field period or a frame period as a CDF calculation area and performs a histogram equalization the image signal of the selected period based on the CDF value. Calculation of the CDF is performed by direct comparison of the pixels of the image, thus eliminating the need to calculate a probability density function for the gray levels. Therefore, it is possible to obtain a high correlation between the input data and the equalized data and to reduce the quantity of hardware.

Abstract: A histogram operating unit comprises: histogram generator which receives input video signals, and creates a histogram of input video signals, a first limiter for receiving a histogram generated by the histogram generator and an externally set first limit level, and restricting the frequency of the histogram created by the histogram generator to within a specified level, and outputting a restricted histogram, a first totaling circuit for calculating the number of samples of video signals produced by the first limiter, second totaling circuit for calculating the number of samples of the input video signals, a first subtractor for subtracting the output of the first totaling circuit from the output of the second totaling circuit, and a corrected histogram generator which receives the output of the first limiter and the output of the first subtractor, and creates the corrected histogram.

Abstract: A television receiver comprising an information extracting circuit for extracting information from a format or content of an input video signal, a video signal processing circuit for processing this video signal by a program or data, a memory for storing the program and data, a CPU for controlling, operating or driving these elements, and a display device for displaying an image. The video signal processing circuit can, under the control of the CPU, decode the signal, correct or set the picture quality such as gradation and sharpness, or adaptively process an on-screen display based on the input video signal. The television receiver is also able to adaptively extend the functions of the television receiver corresponding to various signal formats.

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

Abstract: The present invention relates to a dynamic range expanding apparatus. The dynamic range expanding apparatus realizes a wide dynamic range for a video image while reducing the quantization noise, by determining the brightness transform function based on the combined results of the differential and the integral operation with respect to a brightness distribution function. Moreover, the dynamic range expanding apparatus transforms the color difference signal by using the brightness transform ratio without losing the valance in a color tone.

Abstract: A color correction device is disclosed for correcting color distortion in a displayed television image. Internal circuitry of a television receiver has a color signal distortion characteristic, and the cathode ray tube (CRT) in the television receiver has a gamma characteristic according to which display color is distorted. The color correction device includes an average luminance level calculator for calculating the average luminance level of an image signal displayed by the CRT. Based on the average luminance level calculated by the average luminance lever calculator, a selection is made of appropriate sets from a plurality of available sets of coefficient correction values and a plurality of sets of gamma correction values. The color signal input to the television receiver is then corrected according to the selected sets of coefficient correction values and gamma correction values.

Abstract: An image file for recording natural images, a generation method of the image file and an image display apparatus for displaying image data from this image file. The image file includes image data obtained by digitizing an original, and conversion tables for separating the color tones of the original into R, G and B and converting the changes of the color tones to input luminance-v-output luminance. The image display apparatus controls a color look-up table by the conversion tables read out from the image file, and displays the image data read out from the image file.

Abstract: A method and apparatus are provided to allow threshold values needed for the desired number of gradations to be set through a simple process when converting image data with numerous values into a low number of gradations. The desired number of gradations is achieved without shading being noticeable even for images having shading. The cumulative frequency distribution of the pixels for each brightness is determined from image data having a brightness range with designated gradations. The average brightness and standard deviation of the portion that is primarily background is determined from this cumulative frequency distribution. The first threshold value is determined on the basis of this average brightness and standard deviation, the second through n- 1st threshold values corresponding to the meaningful information are determined on the basis of this first threshold value. An n value conversion process is accomplished using these threshold values.

Abstract: In an image enhancement method is disclosed using a histogram equalization for an input image expressed in a predetermined number of gray levels. While calculating the probability density function of the gray levels of the input image, for use in a histogram equalization, the number of occurrences of each gray level are constrained not to exceed a predetermined value. Then a histogram equalization is performed on the input image based on the calculated probability density (or distribution) function. As a result, the mean brightness of the input image does not change significantly by the histogram equalization. Additionally, noise is prevented from being greatly amplified.

Abstract: In an image processing apparatus, a uniform region whose luminance level change is small is correctly extracted from a noise-containing image. To this end, this image processing apparatus includes an extracting module for extracting a high frequency component of a luminous signal of the image over an entire portion of the image within one screen; histogram generating module for generating a histogram of a luminance level of the luminance signal for one screen on the basis of the output value of the extracting module; coefficient calculating module for analyzing the histogram to calculate a predetermined coefficient indicative of likeness of the uniform region every luminance level; and pixel-position-depending coefficient producing module for establishing a correspondence relationship between the predetermined coefficient calculated by the coefficient calculating module and all of the pixel positions on the image in correspondence to the luminous level of the luminance signal from each of the pixel positions.

Abstract: A video contrast enhancer enhances luminance contrast by dividing each video frame or field into blocks, calculating a mean luminance level for each block, selecting mapping functions on the basis of these mean luminance levels over a series of frames or fields, and mapping the video luminance levels according to the selected mapping functions. Color-saturation contrast is enhanced by modifying the amplitude of the modulated chrominance signal by the histogram equalization method, preferably by making a single linear modification in each period of the chrominance signal, so that color phase is not affected. For video signals with non-picture bands, these enhancements are preferably restricted to the picture area. If a black offset is present, it is preferably removed.

Abstract: Histograms are generated for one or more of the image components. Each histogram is clipped at each end to exclude outlying values and to identify initial minimum and maximum values. Conservatism terms are included in each of the initial minimum and maximum values to generated final minimum and maximum values that are used as thresholds to define the color range used in chroma-key processing. In one embodiment, the first frame of a video sequence is designated as a chroma-key frame that is analyzed to determine the chroma-key color range.

Abstract: An automatic aspect ratio discrimination apparatus for detecting a picture starting position, a picture ending position and a subtitle ending position by generating three histograms segmented by two slice levels S and T at every line from a luminance signal Y at a comparison circuit and counters, judging when the line is black, a picture or a subtitle by inputting the obtained histograms to the comparison circuit, detecting lines varying from black to picture, from picture to black, and from subtitle to black at an edge detection circuit and judging if the lines varying from black to picture and from picture to black are stable in time or not at a temporal filter.

Abstract: A system and method for processing a digital image signal which represents an image can be made to optimally map luminance values versus a tonal reproduction capability of a destination application. Specifically, the system includes a device for partitioning the image into blocks, then combining certain blocks into sectors. An average luminance block value is determined for each block and a difference is determined between the maximum and minimum average luminance block values for each sector. If the difference exceeds a predetermined threshold value, then the sector is labeled as an active sector and an average luminance sector value is obtained from maximum and minimum average luminance block values.

Abstract: A background region of the current image is compared to a reference region to characterize the gain associated with the current image. The values of the unsaturated background pixels of the current image are then adjusted to correct for the characterized gain before encoding the current image. In a preferred embodiment, the reference region is generated based on the previous n frames in the video sequence.

Abstract: Systems and methods for improving the intensity equalization of image data obtained with systems that perceive images with energy sources other than visible light includes a sensor for such data; a converter for transforming the image data from analog form to digital form; a converter for transforming the digital data into black-and-white images containing a predetermined, desired number of gray shades; an intensity equalizer that compensates for the logarithmic effect of visual images on a human eye; an intensity equalizer that compensates for the non-linear effect of the display device for the data; and a converter for transforming the digital intensity-equalized black-and-white image data into analog form for display on a device such as a conventional CRT.

Abstract: A non-linear circuit having a transfer characteristic which is adjustable per amplitude segment of an input signal (Yi) includes a segmenting circuit (11 . . . 15, 21 . . . 25) for obtaining a plurality of amplitude segment signals (Y1 . . . Y5) from the input signal (Yi), and a non-linear segment amplifier circuit (31 . . . 35) coupled to the segmenting circuit (11 . . . 15, 21 . . . 25) for separately multiplying segments (Y1 . . . Y5) of the input signal (Yi) by respective segment gain factors (HM1 . . . HM5) in dependence upon a common gain factor (HMa) derived from the segment gain factors (HM1 . . . HM5) and on the basis of the amplitude segment signals (Y1 . . . Y5) for supplying a signal (Y"s) which is adjustable per amplitude segment of the input signal (Yi). The non-linear circuit may also include an output circuit (37, 39) coupled to the non-linear segment amplifier circuit (31 . . .

Abstract: A picture quality improving circuit for automatically obtaining a corrected image by capturing features of the input video signals. The circuit first compares an input luminance signal with a plurality of reference values, measures the results of the comparison by a plurality of counters and obtains a cumulative histogram within a predetermined period of time. Next, the cumulative histogram signals are stored in a latch circuit for a predetermined period of time, and an interpolation circuit determines and outputs a correction signal corresponding to the input luminance signal by interpolating the cumulative histogram. Accordingly, when a large number of dark signals exist in the input luminance signal, the cumulative histogram signals will describe an upwardly projecting graph, and the dark portions of the signal will be extended in a bright direction. Thereby, the picture quality can be improved.

Abstract: A gradation correcting apparatus, which can be effectively incorporated into various video devices, enables the display of a sub-display within the domain of main-display (i.e. Picture in Picture) and also enables automatic adjustment of each gradation of the display dependent on the characteristics of the respective input signal. By using both a window pulse and a main- and sub-display switching signal, gradation corrections of the displays are carried out such that either no gradation correction is applied to the sub-display or a proper correction is applied according only to the sub-display signal. In this apparatus, the luminance information related to the sub-display and the luminance information related to the main-display excluding that of the sub-display are independently inputted into a signal correction system, thereby allowing individual processing of this information.

Abstract: The invention relates to an intensity correction device for automatically adjusting an intensity of an input video signal by detecting luminance characteristics of the input signal, and provide intensity correction with maintaining clear image by reducing magnitude of the correction signal or by not effecting correction when the luminance level of the input luminance signal is concentrated to a certain luminance level. The intensity correction device includes a histogram memory, a look-up table operating circuit, a look-up table, a maximum value detecting circuit, and an inverter and a multiplier, limiter, or a gain control circuit. By this, when a luminance level of the input video signal is concentrated to a certain luminance level, magnitude of the correction signal can be reduced or made zero. Therefore, by detecting the characteristics of the input image, the intensity of the input video signal can be automatically corrected to the optimal image for providing better picture quality.

Abstract: A gradation corrector for use in a television receiver which can subject a signal at any luminance level to non-linear correction to provide optimum image quality. Memory stores therein luminance histogram of an input signal. On the basis of the data, a circuit detects a total frequency, a circuit detects luminance distribution, and a circuit detects the expanse of the luminance distribution. A circuit calculates a fixed value to be added. Further, a circuit detects a minimum luminance level, and a circuit detects an average luminance level. A circuit calculates an accumulation starting point and a circuit calculates an accumulation stopping point. An adder adds the calculated fixed value to the data in the memory. A circuit accumulates the results in the range from the accumulation starting point to the accumulation stopping point. The accumulation result is stored in memory.