Showing papers on "Bilateral filter published in 1996"

Method and apparatus for compensating errors in a transmitted video signal

Abstract: For concealing channel errors in an image signal divided into a multiplicity of blocks of M×N pixels, M and N being positive integers, a lost region is detected, wherein the lost region is of a polygonal form having a plurality of sides and includes one or more connected lost blocks, each lost block containing a channel error. And then, a reference region of pixels including a plurality of groups of first and second pixels, each group of first pixels being adjacent to a side of the lost region and each group of second pixels being adjacent to a first group of pixels is found. Thereafter, edge pixels having non-zero valued edge magnitudes, an edge magnitude for a pixel representing differences between pixels residing adjacent to the pixel among pixels within the reference region are determined. And each edge point representing an edge pixel having a largest edge magnitude among the edge pixels included in groups of first and second pixels for a side of the lost region is detected. Thereafter, the channel errors of the lost region are rectified by compensating pixels within the lost region based on the edge points and the pixels of the reference region.

Digital image processing method for degraining of film images using distance weighted averaging of target pixel code values

Abstract: A method of digital image processing for degraining (smoothing) of images based on selected averaging of pixels in a neighborhood of pixels surrounding a target pixel to be recalculated. Improvement in the application of the selected average method to images of higher graininess such as might be obtained from higher speed films is achieved by weighting the difference in code values between each neighborhood pixel and the target pixel in accordance with a function that is related to physical distance between the neighborhood pixel and the target pixel. After all target pixels are recalculated using a selected fraction of pixel elements based on their distance weighted difference values, the process is iterated for each target pixel "n" number of times to achieve a desired relative code value of the target pixel to surrounding background pixel code values whereupon a final unweighted averaging operation is performed to achieve the final recalculated value of the target pixel.

Method and device for filtering a picture signal, and encoding/decoding using the same

Abstract: A great decrease of a step, i.e., block distortion, of such as antifact brightness and color, on a block boundary, leads to much visual improvement of picture quality. Against a picture that has been encoded and decoded by block, the smoothing filter characteristics is changed according to quantizing parameter, block activity of a decoded picture, the activity of each pixel of the decoded picture, and the position with respect to a block boundary of a pixel. A smoothing filter utilizes a weighted mean whose weight is the inverse number of a difference between a target pixel and its surrounding pixels. The weighted mean is obtained by adding a certain number to a weight before taking its inverse number. The value to be added is controlled by the parameter. Similarly, the mixing ratio of a pixel value after performing the smoothing filter and a decoded pixel value is changed depending on the parameter. A filter having strong edge preserving property is utilized for the inside of a block, and a filter having weak edge preserving property is utilized for a block boundary. A filter having edge preserving property is utilized for the post/loop filter.

A self-adjusting weighted median filter for removing impulse noise in images

Abstract: An intelligent self-adjusting weighted median filter for removing impulsive noise in images is presented. Three main techniques are developed to implement this self-adjusting weighted median filter: an intelligent classification to divide the image data into the "corrupted" pixels and the "uncorrupted" pixels, an efficient algorithm to find the median output of any weight set, and a realistic training procedure without the noise free image to obtain the proper weights. Our simulations on some test images demonstrate that the proposed filter has less smoothing effect and smaller mean square error (MSE) or mean absolute error (MAE) measurement than the standard median filter. At the same time, the quality of the filter output has been enhanced significantly. Finally, a demonstration chip of this weighted median filter for the 5/spl times/5 window size is also presented.

Image sharpening filter providing variable sharpening dependent on pixel intensity

Abstract: An automatic level-sensitive Laplacian filter for image processing Laplacian filter coefficients and normalization divisors are made a function of intensity on a pixel by pixel basis Pixels indicating a high intensity may be greatly changed by neighboring pixels Pixels indicating a low intensity receive relatively little or no filtering In a specific example embodiment, the intensity range is divided into bands, with a different filter for each band The resulting images are visually sharpened (edge enhanced) with very little impact in darker areas of the image

Image processing apparatus and image processing method for favorably enhancing continuous boundaries which are affected by noise

Abstract: An image processing apparatus which performs a process which enhances incongruous pixel values in an original image, including an object pixel selecting unit for selecting an object pixel out of pixels which compose the original image, a plurality n of filter units, each of which extracts pixel values of a set of pixels, including the selected object pixel, on one of a predetermined surface and a predetermined line which pass through the object pixel, out of pixels in a predetermined range, wherein each predetermined surface and predetermined line is at a different inclination, a relative size comparing unit for comparing pixels values of each set of pixels extracted by each filter unit and specifying a filter unit whose pixel values best approximate to a predetermined standard, and a first pixel value enhancing unit for enhancing a pixel value of the object pixel based on only the pixel values of the specified filter unit.

Method and structure for performing motion estimation using reduced precision pixel intensity values

Abstract: A method of approximating the pixel intensity values of a current block using the pixel intensity values of a search window, wherein the precision of the number of bits used to represent the pixel intensity values is reduced. The pixel intensity values of the pixels in the current block are averaged to determine a first average pixel intensity value. The pixel intensity values of the current block which have a pixel intensity value less than the first average pixel intensity value are averaged to determine a second average pixel intensity value. The pixel intensity values of the current block which have a pixel intensity value greater than the first average pixel intensity value are averaged to determine a third average pixel intensity value. The first, second and third average pixel intensity values are used to determine thresholded pixel intensity values for the current block pixels and the search window pixels, thereby creating a thresholded current block and a thresholded search window. The thresholded current block and thresholded search blocks within the thresholded search window are compared to determine the optimal thresholded search blocks which most closely approximate the thresholded current block. The non-thresholded search blocks corresponding to the optimal thresholded search blocks are compared with the current block (non-thresholded). The non-thresholded search block which most closely approximates the current block is used to estimate the current block.

Dot enhancement for laser imagers

Abstract: Compensation for pixel aberrations in a laser printer is accomplished by selecting pixels (43) to be augmented, and providing additional optical energy to the selected pixels. In one embodiment, the pixels are selected by selecting pixels in combinations in which required pixel augmentation is indicated. The additional optical energy may be applied at the sub-pixel level so that a threshold of energy depletion on an optical photoreceptor (OPR) is not reached where image development would occur. The energy applied at the sub-pixel level results in enhancement of the selected pixels at an adjacent pixel location.

Multi-level resolution lithography

Abstract: A system for lithographic rastering of an image, defined by an array of pixels, onto an image-accepting substrate that allows irradiation of the total pixel pattern in reduced time. The total image is first divided into a collection of one or more geometrically isolated pixel arrays, with all pixels in an array being connected to each other. Each pixel array is decomposed into a fine region, consisting of all image pixels within P pixels of a boundary of that array, where P is a selected positive integer, such as 1, 2 or 3, and a bulk region consisting of all image pixels in that array that are not part of a fine region. A pixel array may include one or more bulk regions and one or more fine regions. A fine region for a pixel array is further decomposed into a first fine sub-region with pixel width at least equal to P1 pixels, where P1 is a selected integer satisfying 2≦P1≦P, and a second fine sub-region with pixel width no greater than P1-1 pixels.

Compression of grey scale images of text

Abstract: An image stored in a memory of a computer as pixels, each pixel including a bit pattern to indicate a grey-scale level. The image is compressed by grouping the pixels of the image into a plurality of regularized groups of pixels. The partitioning of the image can be in groups of four by four adjacent pixels. Groups of pixels having identical bit patterns are identified. The groups of pixels are encoded according to a frequency of groups of pixels having identical bit patterns.

Edge pixel smoothing of block-coded images - has edge pixels processed by edge filter having low=pass stages appropriate to motion vector ranges

Abstract: Video images are subject to a block-based coding process for transmission and each block [BB] consists of a matrix of pixels.The edge pixels [KP] of the block are processed by an edge filter [KGF] to smooth the edges. The filter is based upon two stages that have characteristics such that the transfer function varies with frequency and both have low pass characteristics. The filter stages are effective for different motion vector ranges. The filter is either linear or non-linear.

A Gamma Filter For Multi-look Synthetic Aperture Radar Images

Abstract: This paper describes a new filter for multi-look SAR images, that is based upon their underlying Gamma distribution. The filter’s first step is to estimate the shape and scale parameters of the best fit Gamma distribution from the local image intensity values. This is achieved by a maximum likelihood method that uses a numerical Newton-Raphson iterative technique. By adopting this approach no a priori expectation is placed on the number of looks used to form the multi-look image and thus a measure of the degree of correlation between each look is implicitly contained in the estimate of the shape parameter a. Variation in the underlying image intensity is captured by the estimate for the scale parametera, that depends on both a and the local mean. The filter’s output is then given as the most probable value of the estimated Gamma distribution; this contrasts many extant techniques where the output is based on the mean. The new filter has been applied to simulated and 3-look Jers-1 images. Results show the filter accurate estimates the underlying Gamma distribution’s parameters and reduces speckle noise. To improve performance at edges an adaptive implementation is proposed.

Method of modifying the resolution of a digital image

Abstract: The process provides modification of the resolution of an image obtained by digitising a real image which consists of a given number of pixels of measuring intensity. The process includes investigation and isolation of the contours of the digitised image, and creation of supplementary pixels by interpolation of the intensities of the original pixels situated on the same side of the contour, providing an image of modified resolution. The location of the contours is effected by marking, for each of the neighbouring pixels, the intensity transitions which represent a gradient which exceeds a given threshold. Before the interpolation procedure, the intensities of the original pixels are substituted by weighted values which are a function of the intensities of pixels which are near to the pixel of intensity to be weighted. Weighting is achieved by application of a matrix processing technique.

Efficient computation of the 2-dimensional RGB vector median filter

Abstract: Publisher Summary This chapter discusses that the vector median filter may be used for filtering color images, with all the advantages of the scalar median filter for monochrome images such as preservation of edges. Vector median filtering in two dimensions is computationally demanding because of the need to compute distance metrics among all pairs of pixels within a neighborhood. A straightforward naive implementation of the filter using a 3 X 3 neighborhood on red, green, and blue (RGB) images of 512 X 512 pixels using integer arithmetic requires about 15 seconds of computation on a pentium 100MHz PC. In the chapter, the efficient implementation of this filter has been studied, and a threefold reduction in execution time has been achieved, but the problem of diminishing returns has been encountered.

Apparatus and method for two-dimensional data compression

Abstract: A system and method for compressing data, including image data (204). The image data (204) is formed by a pixel array, the pixel array having target pixels (206) and prior pixels (206), each prior pixel being located in a position within the pixel array prior to each of the targeted pixels. The method of the present invention includes compressing the image data (204) to obtain a compressed image. In the compression step, the pixel array is traversed according to a predetermined non-linear two-dimensional traversing pattern (206). A longest matching prior pixel string (208, 210), if any, is located for each string of target pixels having a string of matching prior pixels. If no matching prior pixel is found for a target pixel, each such target pixel is characterized as an unmatched pixel (212). Finally, the compressed image is encoded (412) and may be either transmitted or stored (416).

A novel error diffusion filter for digital halftoning

Abstract: Error diffusion methods have been used for a long time as a method for correcting the errors resulting when representing each of the samples (pixels) of an analogue image as a single bit binary word. Several filters were previously designed and have been thoroughly analyzed. In this paper a new error diffusion filter is introduced. In this filter the weights and locations of the filter elements are inherently not deterministic. The design of this filter relies on the fact that the image signal can be considered to be of a random nature. The proposed filter produced good quality digitized images.

Restoration filter for bit thinned pixel

Abstract: PROBLEM TO BE SOLVED: To make possible reducing a size of a frame buffer without deteriorating image quality by comparing each pixel with its adjacent pixels, deciding relative values of each pixel with the adjacent pixels, deciding a restoration value of each pixel and adding the restoration value to a cut down pixel previous to a display. SOLUTION: In a restoration process, first, the pixel is shifted. That is, the residual bits of the pixel are shifted to left, and an additional bit is added to a most insignificant bit position. Then, the pixel is compared with each adjacent pixels, and these relative values are decided. Related to respective adjacent pixels larger than the pixel, a restoration offset is increased by one. Similarly, related to respective adjacent pixels smaller than the pixel, the restoration offset is reduced by one. In an applied basic graphics system 100, a graphics processor 104, a frame buffer 108, a video interface 112 and a display device 116 are contained.