Image compression technique
First Claim
1. A method for communicating via a transmission medium of limited bandwidth, an image represented by an image array of pixels each having a first value in a computer-readable storage medium, comprising the steps of:
- identifying pixels of said image array being edge pixels lying on edges of said image;
creating a filled edge array of pixels each corresponding to a respective pixel in said image array,each of the pixels in said filled edge array, which corresponds to an edge pixel of said image array, having a first value that is responsive to the first value of at least one pixel of said image array selected in response to the edge pixel,and each of the pixels in said filled edge array, which does not correspond to an edge pixel of said image array, having a first value that is a function of the first values of at least one of the pixels in said filled edge array which do correspond to edge pixels of said image array;
subtracting said filled edge array from said image array to create a difference array of pixels; and
transmitting signals responsive to said difference array of pixels via said transmission medium.
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Accused Products
Abstract
An image is compressed by identifying edge pixels of the image; creating a filled edge array of pixels each of the pixels in the filled edge array which corresponds to an edge pixel having a value equal to the value of a pixel of the image array selected in response to the edge pixel, and each of the pixels in the filled edge array which does not correspond to an edge pixel having a value which is a weighted average of the values of surrounding pixels in the filled edge array which do correspond to edge pixels; and subtracting the filled edge array from the image array to create a difference array. The edge file and the difference array are then separately compressed and transmitted or stored. The original image is later reconstructed by creating a preliminary array in response to the received edge file, and adding the preliminary array to the received difference array. Filling is accomplished by solving Laplace'"'"'s equation using a multi-grid technique. Contour and difference file coding techniques also are described. The techniques can be used in a method for processing a plurality of images by selecting a respective compression approach for each image, compressing each of the images according to the compression approach selected, and transmitting each of the images as compressed, in correspondence with an indication of the approach selected for the image.
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Citations
45 Claims
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1. A method for communicating via a transmission medium of limited bandwidth, an image represented by an image array of pixels each having a first value in a computer-readable storage medium, comprising the steps of:
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identifying pixels of said image array being edge pixels lying on edges of said image; creating a filled edge array of pixels each corresponding to a respective pixel in said image array, each of the pixels in said filled edge array, which corresponds to an edge pixel of said image array, having a first value that is responsive to the first value of at least one pixel of said image array selected in response to the edge pixel, and each of the pixels in said filled edge array, which does not correspond to an edge pixel of said image array, having a first value that is a function of the first values of at least one of the pixels in said filled edge array which do correspond to edge pixels of said image array; subtracting said filled edge array from said image array to create a difference array of pixels; and transmitting signals responsive to said difference array of pixels via said transmission medium. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24)
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25. A method for communicating, via a transmission medium of limited bandwidth, a plurality of images each being represented by a respective image array of pixels in a computer-readable storage medium, comprising the steps of:
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selecting a respective compression approach for each of said images from a plurality of available compression approaches including first and second compression approaches; compressing each of said images according to the compression approach selected for the image; and transmitting via said transmission medium each of said images as compressed, in correspondence with an indication of the approach selected for the image, wherein said first compression approach comprises, for a subject image, the steps of; identifying edge pixels of the image array representing said subject image which lie at edges of said subject image; and encoding an indication of each of said edge pixels in correspondence with a value of each of said edge pixels. - View Dependent Claims (26, 27, 28, 29)
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30. A method for forming a reconstructed image, comprising the steps of:
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receiving over a transmission medium having limited bandwidth an indication of pixels in a destination image array which are to be edge pixels lying on edges of said image, and a first value for each of said edge pixels; forming said destination image array of pixels in a computer-readable storage medium such that each given pixel in said array which is one of said edge pixels has a respective first value substantially equal to the first value received over said transmission medium for a given edge pixel; and solving Laplace'"'"'s equation over the first values of said destination image array, taking as boundary conditions the first values of each of said edge pixels. - View Dependent Claims (31)
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32. A method for forming a reconstructed image, comprising the steps of:
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receiving over a transmission medium having limited bandwidth an indication of pixels in a destination image array which are to be edge pixels lying on edges of said image, and a first value for each of said edge pixels; forming said destination image array of pixels in a computer-readable storage medium such that each given pixel in said array which is one of said edge pixels has a respective first value substantially equal to the first value received over said transmission medium for said given edge pixel, and such that each pixel in said destination image array which is not one of said edge pixels has a respective first value which is a function of the first values of edge pixels in said destination image array; receiving over said transmission medium a difference image array of pixels; and adding said destination image array and said difference image array. - View Dependent Claims (33, 34, 35, 36, 37)
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38. Apparatus for solving Laplace'"'"'s equation over the values of respective elements in a first array having a size of M elements in a first dimension and N elements in a second dimension, the values of at least some of elements in said first array being fixed, comprising:
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means for preparing a second level array having M/A elements in said first dimension and N/B elements in said second dimension, where A and B are predetermined integers at least one of which is greater than 1, each element in said second level array corresponding to a respective element in said first array, each element in said second level array having a value fixed at the value of the corresponding element in said first array if the corresponding element in said first array is fixed, each element in said second level array having a value fixed at a first predefined function of the values of those elements in a predefined neighborhood of the corresponding element in said first array which are fixed if the corresponding element in said first array is not fixed but at least one element in said neighborhood of the corresponding element in said first array is fixed; means for solving Laplace'"'"'s equation over the values of said second level array of elements, taking as boundary conditions those values of said second level array which are fixed; means for setting the value of each element in said first array which is not fixed, the neighborhood of which element includes at least one element whose value is fixed, to a second predefined function of the values of those elements in said neighborhood which are fixed; means for, after solving Laplace'"'"'s equation over the values of said second level array, setting the value of each element in said first array which is not fixed and which corresponds to an element of said second level array, the neighborhood of which element in said first array includes no element whose value is fixed, to the value of the corresponding element of said second level array; means for, after solving Laplace'"'"'s equation over the values of said second level array, setting the value of each element in said first array which is not fixed and which does not correspond to an element of said second level array, the neighborhood of which element in said first array includes no element whose value is fixed, to a third predefined function of the values of those elements in said second level array which correspond to an element in the neighborhood of the element in said first array; and means for subsequently solving Laplace'"'"'s equation over the values of said first array, taking as boundary conditions those values of said first array which are fixed, and taking as initial values those values of said first array which are not fixed. - View Dependent Claims (39, 40, 41, 42)
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43. Apparatus for solving Laplace'"'"'s equation over the values of respective elements in a first level array having a size of M elements in a first dimension and N elements in a second dimension, the values of at least some of elements in said first level array being fixed, comprising:
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means for preparing a second level array having M/2 elements in said first dimension and N/2 elements in said second dimension, each element in said second level array corresponding to a respective element in said first level array, each element in said second level array having a value fixed at the value of the corresponding element in said first level array if the corresponding element in said first level array is fixed, each element in said second level array having a value fixed at a weighted average of the values of those elements in a 3 by 3 element neighborhood of the corresponding element in said first level array which are fixed if the corresponding element in said first level array is not fixed but at least one element in said 3 by 3 element neighborhood of the corresponding element in said first level array is fixed; means for invoking said means for preparing, repeatedly for successively coarser level arrays until a predefined coarsest level array is prepared; means for, after said coarsest level array is prepared, solving Laplace'"'"'s equation over the values of said coarsest level array of elements, taking as boundary conditions those values of said coarsest level array which are fixed; means for setting the value of each element in each level array which is not fixed, the 3 by 3 element neighborhood of which element includes at least one element whose value is fixed, to a weighted average of the values of those elements in said 3 by 3 element neighborhood which are fixed; means for, after solving Laplace'"'"'s equation over the values of said coarsest level array, setting the value of each element in the next finer level array which is not fixed and which corresponds to an element of said coarsest level array, the 3 by 3 element neighborhood of which element in said next finer level array includes no element whose value is fixed, to the value of the corresponding element of said coarsest level array; means for, after solving Laplace'"'"'s equation over the values of said coarsest level array, setting the value of each element in said next finer level array which is not fixed and which does not correspond to an element of said coarsest level array, the 3 by 3 element neighborhood of which element in said next finer level array includes no element whose value is fixed, to a weighted average of the values of those elements in said coarsest level array which correspond to an element in the 3 by 3 element neighborhood of the element in said next finer level array; means for, after setting values in the next finer level array, solving Laplace'"'"'s equation over the values of said next finer level array, taking as boundary conditions those values of said next finer level array which are fixed, and taking as initial values those values of said next finer level array which are not fixed; and means for invoking the means for setting values in the next finer level array and the means for solving Laplace'"'"'s equation over values of the next finer level array, repeatedly for successively finer level arrays until Laplace'"'"'s equation has been solved over values of the first level array. - View Dependent Claims (44, 45)
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Specification