Showing papers on "Bilateral filter published in 1992"

Method and apparatus for processing block coded image data to reduce boundary artifacts between adjacent image blocks

Abstract: A method and apparatus for processing block coded image data wherein each block comprises a plurality of pixels. A local pixel is selected from a first block of pixels. The selected pixel is preferably near a border between the first block of pixels and a second block of pixels. At least one external pixel is selected from the second block of pixels. The selected external pixel(s) is (are) also near the border. The selected local pixel is modified to reduce the difference between the local pixel and the selected external pixel(s). The selected pixel value is modified as follows. A low pass filter coefficient is selected for each selected local pixel value and for each selected external pixel value. The selected local pixel value and the external pixel values are each multiplied by their corresponding low pass filter coefficient. The products of these multiplications are summed together to form a low pass filtered pixel value.

Three-dimensional median and recursive filtering apparatus and method for video image enhancement

Abstract: According to a presently preferred embodiment of the invention, image enhancement apparatus for digital video images comprises a two-stage filter comprising a median filter and a recursive filter The median filter operates in one, two, and three dimensions wherein the cluster of pixels framing the center pixel are ranked, and the median value of the pixel cluster is chosen as the correct pixel value The pixel cluster configuration is selectable, as are the planes where the pixels are located Multiple weights may be given to the appropriate median filter inputs A motion detector is used to prevent replacement of each pixel by its pixel cluster median value when there is excessive motion Finally an adjustable pixel-replacement threshold is defined Each pixel must deviate from its median value before it is replaced by that value In the presence of rapid motion in the picture, the operation of the median filter is reduced or halted by a properly derived motion signal according to the present invention, thus preventing motion artifacts from occurring

Image reduction of binary images using filtering processing

Abstract: An image reduction system which reduces binary level images is disclosed. In the system, a reduction pixel value is determined by using, as reference pixels for a filter operation: a plurality of surrounding pixels including an object pixel to be reduced; and reduced pixels, from among pixels which have already been reduced, said reduced pixels being at least; a reduced pixel located before the pixel to be determined: a reduced pixel, located on the preceding line, which lies directly above the pixel to be determined; and a reduced pixel before said reduced pixel located on the preceding line. When a pixel referenced during the filter operation is included in a specific pattern, an exception process for correcting binary level results is provided.

Digital image forming apparatus using subdivided pixels

Abstract: In a method of forming an image in a form of pixels, the density distribution around a target pixel is obtained by processing image signals of pixels neighboring the target pixel. The target pixel is sub-divided into a plurality of sub-pixels which form of matrix of n rows×m columns. The sub density distribution of the sub-pixels in the target pixel is assumed from the density distribution of the neighboring pixels. The density of each of sub-pixels is determined by multiplying the density of the target pixel, by a constant P and a density ratio of the corresponding sub-pixels in the sub density distribution.

Method for inspecting and reading display element

Abstract: PURPOSE:To inspect light quantity emitted by a pixel with high accuracy by regarding an integrated value of detected light quantities from individual sensor pixels among sensor pixels group relating to a pixel image as the light quantity of pixels to be inspected. CONSTITUTION:Luminous intensity distribution 2 of the pixel image in which respective pixels are in lighting state is shown with a relation between a pixel image region 1 and sensor pixels 3 are shown with a relation between respective positions. The pixel image region of the noticed pixel on the sensor pixel surface is denoted by 1T, the luminous intensity distribution characteristic of the image region is denoted by 2T, respective pixel image regions of left and right sides pixels adjacent to the noticed pixel are denoted by 1NL, 1NR, the luminous intensity distribution characteristics of the image regions are respectively denoted by 2NL, 2NR and sensor pixels relating to the noticed pixel are denoted by 31 to 37. In order to detect all rays of light emitted from the pixel to be inspected, light quantities detected by all sensor pixels relating to the pixel image to be detected are summed. That is, the summed value of light quantities 42, 41, 43 detected by sensor pixels 33 to 35 is read-out as light quantity emitted from the pixel to be inspected.

Method and system for thinning images

Abstract: Image data is subjected to a thinning process so as to derive a medial axis for each image. Boolean image data is reduced to lines and/or dots, each line generally being a centroid line of an image. The thinning process uses a change look-up table which is addressed using values from pixels in the neighborhood of a particular pixel which is the target for possible change. Pixels in the neighborhood which are to be evaluated are given a weight by use of a weight look-up table and the weight of the pixel is multiplied by the value of the pixel. Alternately, the weight of the pixel may be added to the pixel value. The pixels in the neighborhood of a target pixel (i.e., pixel which is being evaluated for possible removal) have their weights and values taken into account by a summation of the results of the multiplication (or addition) performed for each pixel so as to provide an address used to address a change look-up table which supplies an output indicative of change in the target pixel. The thinning is accomplished by a floating point processor using a pipelined procedure.

Optical correlation using reduced resolution filters

Abstract: We determined the performance of an optical correlator as the filter SLM was reduced in resolution by a factor of M in a linear dimension. Our configuration allowed a constant reduction, by a factor of M 2 , in the amount of data used to describe the filter when compared to using a filter at full resolution. Reducing the resolution of the filter is shown to primarily affect its impulse response by the addition of copies of the filter image. We provide both general expressions for performance measures and guidelines for minimizing the distortion induced as the resolution of a filter is decreased. Furthermore, we show the effect of reducing the resolution of a binary phase-only filter on autocorrelation experiments and cross-correlation experiments containing competing objects. We obtained experimental results with an optical correlator with a magneto-optic SLM of 128 x 128 pixels in the input plane and a filter of 64 x 64 pixels. The results showed that our arrangement can provide comparable results to a full-resolution filter when the resolution is decreased by a factor of M and the object within the filter images is less than N / M x N / M pixels in size.

Method of resolution conversion

Abstract: A method of resolution conversion for use in a system (10) of the type capable of manipulating digital images represented by a plurality of original image pixels is provided. In the preferred embodiment, the system (10) has a memory (100) for storing images and an image output terminal (14). Additionally, the method includes a step of deriving an intensity value (Z) for a selected output pixel (108) in a set of (106) output pixels from a plurality of input pixels (104) in a set of input pixels, each of the plurality of input pixels (104) having a corresponding intensity value (I) contributing to the intensity value (Z) of the selected output pixel. The step of deriving the intensity value (Z) of the selected output pixel preferably comprises the steps of mapping, in the memory, the set of output pixels to the set of input pixels so that each of the plurality of input pixels (104) is adjacent the selected output pixel (108), as well as reading the plurality of input pixels (104) from the memory. After determining a correlation value for each of the plurality of input pixels (104) with a correlation function (W), the correlation values of the plurality of input pixels (104) can be summed with the corresponding respective intensity values of the plurality of input pixels (104) to obtain the intensity value (Z) of the selected output pixel (108).

Pixel dividing method of color filter

Abstract: PURPOSE:To apply the pixel dividing method to any of a graphic display, a character display, and a line drawing display by slanting curving pixel border lines in picture elements in a pixel communicating direction. CONSTITUTION:The color filter 21 has one picture element 22 composed of colored pixels R, G, and B and pixels of the same colors among respective pixels R, G, and B communicate in the front-rear direction. Border lines 23 which section pixels R and G in respective picture elements 22 and border lines 24 which section pixels G and B are slanted or curved in the communicating direction of the pixels R, G, and B. The border lines 23 and 24 are longer than the border lines between pixels R and B of adjacent picture elements 22 which adjoin in the right-left direction. Therefore, the coupling force between pixels in picture elements based upon the border line length is larger than the coupling force between pixels in picture elements which communicates in a direction wherein pixels to not communicate. Consequently, color mixture of pixels in a picture element is made sharp and a multicolored display is enabled by a stripe array. Further, linearity in the pixel succession direction is eliminated by a mosaic array and a triangle array.

Detecting method of small objects in a natural environment

Abstract: A method and circuit arrangement for detecting small objects in a natural environment, using an electro-optical sensor, scanning the environment, followed by an evaluating unit and an image display device which may be provided. To be able to extract small compact objects out of their natural environment and to suppress irrelevant background information, a digital image is filtered by at least three non-linear filter branches operating in parallel, in such a manner that each filter determines the maximum and minimum of brightness values of in each case one of at least three pixel reference sets. The central pixel is marked in dependence on a threshold value and each marked pixel is enlarged by including the nearest adjacent pixels. The number of pixels marked is counted for a complete image. The current counting results are compared with fixed limits and used for controlling the threshold values. Finally, the enlarged marked pixels are combined by a logic AND operation to form a result set, and the coordinate values of all end result set elements determined in this manner are stored as detected pixels.

Detecting method and device of small objects in a natural environment

Abstract: of EP0539653A method and circuit arrangement for detecting small objects in a natural environment, using an electro-optical sensor, scanning the environment, followed by an evaluating unit and an image display device which may be provided. To be able to extract small compact objects out of their natural environment and to suppress irrelevant background information, a digital image is filtered by at least three non-linear filter branches operating in parallel, in such a manner that each filter determines the maximum and minimum of brightness values of in each case one of at least three pixel reference sets. The central pixel is marked in dependence on a threshold value and each marked pixel is enlarged by including the nearest adjacent pixels. The number of pixels marked is counted for a complete image. The current counting results are compared with fixed limits and used for controlling the threshold values. Finally, the enlarged marked pixels are combined by a logic AND operation to form a result set, and the coordinate values of all end result set elements determined in this manner are stored as detected pixels.

Four direction adaptive error concealment system for component digital television signals.

Abstract: An error concealment technique for component television signal systems evaluates video pixels surrounding an erroneous video pixel P(0,0) in four different directions, and determines which direction of surrounding pixels provides the best replacement value for the erroneous pixel. The technique includes calculating disparity values in each direction, weighting the disparity values with coefficients modified in response to any corrupted pixels in the pixels surrounding the erroneous pixel. The coefficients also may be adjusted in accordance with critical picture material. The weighted and modified disparity values are compared, and the preferred least disparity value is selected. The video pixels are supplied to four filters (44,46,48,50), wherein optimum filter coefficients are simulated to provide the maximum bandwidth and minimum ripple in the frequency response to any corrupted pixels in the surrounding pixels. The least disparity value selects the preferred filter and the filtered pixel value thereof is used to replace the erroneous pixel.

A method for removing drop-out noise

Abstract: The invention relates to a method for filtering off drop-out noise in a television picture. A median filter is used for the filtering, and pixels to be used in the filtering are selected, in addition to the pixel to be examined, among such pixels which have a vertical position different from the former and which may be in a picture different from that of the examined pixel. Drop-outs are effectively filtered without reducing the picture quality by using e.g. a median filter, the inputs of which are selected so that a single pixel must not act on the majority of the filter inputs, that the majority of the filter inputs must comprise pixels from the original line, and that the majority of the filter inputs must comprise pixels from the examined field. Drop-out noise in the picture can be localized with a detector, which utilizes information from more than one picture.

An alpha -trimmed mean filter controlled by local parameters

Abstract: The authors formulate a general model-based filter that behaves as a rank filter in the presence of lines and borders and as a mean filter otherwise. The model is expressed in terms of local normalized parameters and the filter equation is a function of these parameters. Furthermore, they introduce some geometrical information taking the filter into account of the local structure in the neighbourhoods of the pixels. >