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In a first aspect, a method and an apparatus for processing an image classifies the image content of a portion of the image, and in response thereto, selects between linear interpolation (e.g., cubic) and non-linear interpolation (median) methods to interpolate data points for the portion of the ima

In a first aspect, a method and an apparatus for processing an image classifies the image content of a portion of the image, and in response thereto, selects between linear interpolation (e.g., cubic) and non-linear interpolation (median) methods to interpolate data points for the portion of the image. In one embodiment, non-linear interpolation is selected if the image content of the portion of the image is bi-level, or if portion of the image includes an edge and lacks a specified measure of correlation along a line. Linear interpolation is used in portions where the image content does not include an identified edge and in portions where there is an identified edge in combination with an identified edge direction or a path of isobrightness. In a second aspect, a method and apparatus for use in classifying the image content of a portion of an image calculates a reference value from pixel values for a portion of an image and generates data indicative of which pixel values are greater than the reference value and which pixel values are less than the reference value.

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1. A method of processing an image comprising the steps of;receiving image data representative of pixels in an image;classifying the image content of a first portion of the image based on a first portion of the image data representative of pixels in the first portion of the image;selecting a type of

1. A method of processing an image comprising the steps of;receiving image data representative of pixels in an image;classifying the image content of a first portion of the image based on a first portion of the image data representative of pixels in the first portion of the image;selecting a type of interpolation from a group including linear interpolation and non-linear interpolation in response to the step of classifying the image content of the first portion of the image; andusing the selected type of interpolation to generate interpolated pixel data representative of an interpolated pixel adjacent at least one of the pixels in the first portion of the image;wherein the step of classifying the image content of a first portion of the image includes the step of defining a processing window representative of an array of the pixels in the image, the array having N rows and M columns, wherein N and M each have a magnitude of at least four,wherein the step of using the selected type of interpolation to generate interpolated pixel data includes generating at least one of pixel values X, Y, Z indicative of three interpolated pixels, the interpolated pixel value X being indicative of an interpolated pixel disposed between a pixel in a second row and a second column of the array and a pixel in the second row and the third column of the array, the interpolated pixel value Y being indicative of an interpolated pixel disposed between the pixel in the second row and the second column of the array and a pixel in a third row and the second column of the array, and the interpolated pixel value Z being indicative of an interpolated pixel disposed between the pixel in the second row and the second column of the array and a pixel in the third row and the third column of the array. 2. The method of claim 1 further comprising the steps of:classifying the image content of a second portion of the image by processing a second portion of the image data representative of the second portion of the image;selecting a type of interpolation from a group including linear interpolation and non-linear interpolation in response to the step of classifying the image content of the second portion of the image; andusing the selected type of interpolation to generate interpolated pixel data representative of an interpolated pixel adjacent at least one of the pixels in the second portion of the image. 3. The method of claim 2 further comprising the step of selecting the second portion of the image to be overlapping with the first portion of the image. 4. The method of claim 1 further including the steps of:dividing the image into a plurality of overlapping portions;performing the steps of classifying the image content, selecting a type of interpolation, and using the selected type of interpolation, for at least a majority of the plurality of overlapping portions of the image. 5. The method of claim 1 wherein the step of selecting a type of interpolation includes the step of selecting a type of interpolation from a group including polynomial interpolation, and at least one of median interpolation and modal interpolation. 6. The method of claim 1, wherein the step of using the selected type of interpolation to generate interpolated pixel data includes the steps of:selecting a pixel;interpolating a first pixel offset in a first direction from the selected pixel using linear interpolation along a line including the first direction; andinterpolating a second pixel offset in a second direction from the selected pixel using linear interpolation along a line including the second direction. 7. The method of claim 1 wherein the step of classifying the image content of the first portion of the image further comprises the step of determining whether the image content of the first portion of the image includes an edge and less than a specified measure of correlation along a predetermined line, and the step of selecting a type of interpolation includes the step of selecting non -linear interpolation to interpolate a pixel disposed on the line, in cases where it has been determined that the image content of the first portion of the image includes an edge and less than the specified measure of correlation along the line. 8. The method of claim 7 wherein the step of determining whether the image content of the first portion of the image includes an edge extending from a side of the first portion of the image to an opposite side of the first portion of the image. 9. The method of claim 1 wherein the step of classifying the image content of the first portion of the image further comprises the step of determining whether the image content of the first portion of the image has at least a specified measure of correlation along a predetermined line and the step of selecting a type of interpolation includes the step of selecting linear interpolation along the predetermined line to interpolate a pixel disposed on the line in cases where it has been determined that the image content of the first portion of the image has at least the specified measure of correlation along the line. 10. The method of claim 7 wherein the step of classifying the image content of the first portion of the image further comprises the step of determining whether the image content of the first portion of the image has at least a specified measure of correlation along a predetermined line and the step of selecting a type of interpolation includes the step of selecting linear interpolation along the predetermined line to interpolate a pixel disposed on the line in cases where it has been determined that the image content of the first portion of the image has at least the specified measure of correlation along the line. 11. The method of claim 1 wherein the first portion of the image data comprises a plurality of pixel values each representative of an associated one of the pixels in the image, and the step of classifying the image content of the first portion of the image includes the steps of:calculating a reference value from the plurality of pixel values;determining, for each of the pixel values, data indicative of whether the pixel value is in a range of values including the reference value, greater than the range of values including the reference value, or less than the range of values including the reference value; andusing the data to determine whether the first portion of the image includes an edge and at least the specified measure of correlation along the line. 12. A method of processing an image comprising the steps of;receiving image data representative of pixels in an image;classifying the image content of a first portion of the image based on a first portion of the image data representative of pixels in the first portion of the image;selecting a type of interpolation from a group including linear interpolation and non-linear interpolation in response to the step of classifying the image content of the first portion of the image; andusing the selected type of interpolation to generate interpolated pixel data representative of an interpolated pixel adjacent at least one of the pixels in the first portion of the image;wherein the first portion of the image data comprises a plurality of pixel values each representative of an associated one of the pixels in the image, the plurality of pixel values comprising a number of different values, the step of classifying includes the step of determining whether the number of different values is no greater than a threshold value that is no greater than twenty percent of a total number of the pixel values, and the step of selecting a type of interpolation includes the step of selecting a non-linear type of interpolation in cases where it has been determined that the number of different values is no more than the threshold value. 13. The method of claim 12 wherein the step of processing includes the step of specifying a threshold value that is less than three. 14. A method for use in generating an enlargement of an image having pixels disposed in a plurality of rows and columns, a pixel p ij being disposed in a row i, and a column j of the image, the method comprising the steps of:a) receiving pixel values each representative of an associated one of the pixels of the image, a pixel value x ij being representative of the pixel p ij in the row i, and the column j of the image;b) dividing the pixel values into a plurality of overlapping portions each representative of pixels in an associated portion of the image;c) defining a processing window comprising a first one of the overlapping portions of the pixel values associated with an array of pixels of the image, the array comprising N rows and M columns of the pixels in the image, N and M each having a magnitude of at least four, the portion of the pixel values comprising a number of different values;d) determining whether the number of different values is no more than a threshold value having a magnitude no greater than twenty percent of a count of the pixel values;e) generating, in cases where it has been determined that the number of different values is no more than the threshold value, at least one interpolated pixel value from the portion of pixel values using at least one of median filtering and modal filtering;f) determining, at least in other cases, whether the array of pixels in the image has an edge and at least a specified measure of correlation along a predetermined line;g) using polynomial filtering in at least one direction, to generate, at least in cases where the array of pixels does not have an edge, at least one interpolated pixel value from the portion of pixel values;h) determining at least in cases where the portion of the image has an edge, whether the image content of the first portion of the image has correlation in a predetermined direction;i) generating, in cases where it has been determined that the portion of the image has an edge but does not have at least the specified measure of correlation along the line, at least one interpolated pixel value from the portion of pixel values using non-linear filtering;j) generating, in cases where it has been determined that the portion of the image has at least the specified measure of correlation along the line, at least one interpolated pixel value from the portion of pixel values using linear filtering; andk) repeating the steps of c) through j) for a second one of the plurality of overlapping portions of image data. 15. A method of processing an image comprising the steps of;receiving image data representative of pixels in an image;receiving data indicative of a classification of a first portion of the image based on a first portion of the image data representative of pixels in the first portion of the image; selecting a type of interpolation from a group including linear interpolation and non-linear interpolation in response to the data indicative of the classification of the first portion of the image; andusing the selected type of interpolation to generate interpolated pixel data representative of an interpolated pixel adjacent at least one of the pixels in the first portion of the image;wherein classification of the image content of a first portion of the image includes defining a processing window representative of an array of the pixels in the image, the array having N rows and M columns, wherein N and M each have a magnitude of at least four,wherein the step of using the selected type of interpolation to generate interpolated pixel data includes generating at least one of pixel values X, Y, Z indicative of three interpolated pixels, the interpolated pixel value X being indicative of an interpolated pixel disposed between a pixel in a second row and a second column of the array and a pixel in the second row and the third column of the array, the interpolated pixel value Y being indicative of an interpolated pixel disposed between the pixel in the second row and the second column of the array and a pixel in a third row and the second column of the array, and the interpolated pixel value Z being indicative of an interpolated pixel disposed between the pixel in the second row and the second column of the array and a pixel in the third row and the third column of the array. 16. An apparatus for processing an image, the apparatus comprising:means for receiving image data representative of pixels in an image;means for classifying the image content of a first portion of the image based on a first portion of the image data representative of pixels in the first portion of the image;means for selecting a type of interpolation from a group including linear interpolation and non-linear interpolation in response to the step of classifying the image content of the first portion of the image; andmeans for using the selected type of interpolation to generate interpolated pixel data representative of an interpolated pixel adjacent at least one of the pixels in the first portion of the image;wherein the means for classifying defines a processing window representative of an array of the pixels in the image, the array having N rows and M columns, wherein N and M each have a magnitude of at least four,wherein the means for using the selected type of interpolation to generate interpolated pixel data generates at least one of pixel values X, Y, Z indicative of three interpolated pixels, the interpolated pixel value X being indicative of an interpolated pixel disposed between a pixel in a second row and a second column of the array and a pixel in the second row and the third column of the array, the interpolated pixel value Y being indicative of an interpolated pixel disposed between the pixel in the second row and the second column of the array and a pixel in a third row and the second column of the array, and the interpolated pixel value Z being indicative of an interpolated pixel disposed between the pixel in the second row and the second column of the array and a pixel in the third row and the third column of the array. 17. An apparatus for processing an image, the apparatus comprising:a selector having an input to receive image data representative of pixels in an image and an output to provide data representative of pixels in a first portion of the image;a classifier having an input to receive the data representative of pixels in the first portion of the image and an output to data indicative of the image content of the first portion of the image;an adaptive interpolator having an input to receive the data indicative of the image content of the first portion of the image, and having an output to provide interpolated pixel data representative of an interpolated pixel adjacent at least one of the pixels in the first portion of the image, the interpolated pixel data being generated in accordance with a type of interpolation selected from a group including linear interpolation and non-linear interpolation in response to the data indicative of the image content of the first portion of the image;wherein the classifier defines a processing window representative of an array of the pixels in the image, the array having N rows and M columns, wherein N and M each have a magnitude of at least four,wherein the adaptive interpolator generates at least one of pixel values X, Y, Z indicative of three interpolated pixels, the interpolated pixel value X being indicative of an interpolated pixel disposed between a pixel in a second row and a second column of the array and a pixel in the second row and the third column of the array, the interpolated pixel value Y being indicative of an interpolated pixel disposed between the pixel in the second row and the second column of the array and a pixel in a third row and the second column of the array, and the interpolated pixel value Z being indicative of an interpolated pixel disposed between the pixel in the second row and the second column of the array and a pixel in the third row and the third column of the array.