Apparatus and method for 2-dimensional data compression

• US 5,710,719 A
• Filed: 10/19/1995
• Issued: 01/20/1998
• Est. Priority Date: 10/19/1995
• Status: Expired due to Term

• Current Assignee: Google LLC (Alphabet Inc.)
• Original Assignee: America Online Inc. (Warner Bros. Discovery, Inc.)
• Inventors: Houle, Paul
• Primary Examiner(s): Ramirez, Ellis B.
• Application Number:
  US08/545,513
• Time in Patent Office: 824 Days
• Field of Search: 364/514.12, 364/715.02, 382/244, 382/245, 348/418, 341/106
• US Class Current: 382/232
• CPC Class Codes: G06T 9/40 Tree coding, e.g. quadtree, octree
• CPC Class Codes: H04N 19/13 Adaptive entropy coding, e.g. adaptive variable length coding [AVLC] or context adaptive binary arithmetic coding [CABAC]
• CPC Class Codes: H04N 19/593 involving spatial prediction techniques
• CPC Class Codes: H04N 19/60 using transform coding
• CPC Class Codes: H04N 19/91 Entropy coding, e.g. variable length coding [VLC] or arithmetic coding

Abstract

A system and method for compressing data, including image data. The image data is formed by a pixel array, the pixel array having target pixels and prior pixels, each prior pixel being located in a position within the pixel array prior to each of the target pixels. The method of the present invention includes compressing the image data to obtain a compressed image. In the compression step, the pixel array is traversed according to a predetermined non-linear two-dimensional traversing pattern. A longest matching prior pixel string, 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. Finally, the compressed image is encoded and may be either transmitted or stored.

Claims

1. A method for compressing an original image, the original image having a pixel array, the pixel array having target pixels and prior pixels, each prior pixel being located in a position within the pixel array prior to each target pixel, the method comprising the steps of:

(a) compressing the original image to obtain a compressed image, including repeatedly;

(1) traversing the pixel array according to a predetermined non-linear traversing pattern to locate a prior pixel, if any, matching a target pixel;

(2) if such a matching prior pixel is located, then comparing corresponding target pixels and prior pixels linearly following the matched target pixel and prior pixel to locate a matching prior pixel string, if any;

(3) repeating steps (1) and (2) to locate a longest matching prior pixel string;

(4) generating a copy token as a compressed representation of each such longest matching prior pixel string; and

(5) generating a literal token for each target pixel having no matching prior pixel.

3. The method of claims 1 or 2, further including the step of further compressing the compressed image by encoding the compressed image using a Huffman encoding algorithm.

4. The method of claim 3 wherein all possible copy tokens and all possible literal tokens form a token set, the method further comprising the steps of:

(a) generating a Huffman tree for the token set;

(b) outputting the Huffman tree; and

(c) outputting the compressed image after outputting the Huffman tree.

5. The method of claim 4, further comprising the steps of:

(a) before outputting the Huffman tree, encoding the Huffman tree in a compressed format to obtain a compressed Huffman tree;

(b) decoding the encoded compressed image using the Huffman tree; and

(c) decompressing the decoded compressed image to obtain the original image.

6. The method of claim 1, further comprising the step of:

(a) subsampling the original image before compressing the original image.

7. The method of claim 1 wherein the predetermined non-linear traversing pattern has a fixed length.

8. The method of claim 6 wherein the predetermined non-linear traversing pattern is empirically determined.

9. The method of claim 8 wherein the predetermined non-linear traversing pattern has a plurality of pixel offsets, the first 24 of the plurality of pixel offsets being as follows:

space="preserve" listing-type="tabular">______________________________________ 23 18 16 7 17 19 24 21 14 6 3 9 15 22 11 8 4 1 5 10 20 12 13 2 # ______________________________________

where "#" designates a pixel position being encoded and the numbers 1 through 24 designate the first 24 pixel offsets, in order.

10. The method of claims 1 or 2, wherein each longest matching data string has a string of matching pixels corresponding to a string of target pixels, and wherein, in locating the longest matching data strings, each pixel in the pixel array has a tolerance, whereby the string of matching pixels in a longest matching data string are considered to match a string of target pixels if each of the matching pixels in the string of matching pixels falls within the tolerance of the corresponding target pixel in the string of target pixels.

2. A method for compressing an original image to obtain a compressed image, the original image having a pixel array, the pixel array having target pixels and prior pixels, each prior pixel being located in a position within the pixel array prior to each target pixel, the method comprising the steps of:

(a) repeatedly traversing the pixel array according to a predetermined non-linear traversing pattern to locate a longest matching prior pixel string, if any, matching a target pixel string;

(b) generating a copy token referencing such longest matching prior pixel string as a compressed representation of such matching target pixel string; and

(c) generating a literal token for each target pixel having no matching prior pixel.

11. A system for compressing an original image to obtain a compressed image, the original image having a pixel array, the pixel array having target pixels and prior pixels, each prior pixel being located in a position within the pixel array prior to each of the target pixels, the system comprising:

(a) means for repeatedly traversing the pixel array according to a predetermined non-linear traversing pattern to locate a longest matching prior pixel string, if any, matching a target pixel string;

(b) means for generating a copy token referencing such longest matching prior pixel string as a compressed representation of such matching target pixel string; and

(c) means for generating a literal token for each target pixel having no matching prior pixel.

12. A computer program for compressing an original image to obtain a compressed image, the original image having a pixel array, the computer program being tangibly stored on a media readable by a computer system, the computer program being adapted for configuring the computer system upon being read and executed by the computer system to perform the functions of:

(a) repeatedly traversing the pixel array according to a predetermined non-linear traversing pattern to locate a longest matching prior pixel string, if any, matching a target pixel string;

(b) generating a copy token referencing such longest matching prior pixel string as a compressed representation of such matching target pixel string; and

(c) generating a literal token for each target pixel having no matching prior pixel.

13. A method for compressing image data, the image data comprising an array of pixels, the array of pixels having an initial target pixel and prior pixels, each prior pixel being located before the initial target pixel within the array of pixels, the method comprising the steps of:

(a) traversing the image data according to a reverse non-linear traversing pattern in a reverse direction within the array of pixels;

(b) locating an initial matching prior pixel, if any, that matches the initial target pixel;

(c) if an initial matching prior pixel is located, traversing, according to a linear traversing pattern in a forward direction within the array of pixels, both the pixels succeeding the initial target pixel and the pixels succeeding the initial matching prior pixel until a target pixel succeeding the initial target pixel does not match a prior pixel succeeding the initial matching prior pixel, thereby defining a matching data string;

(d) continuing traversing the image data in the non-linear traversing pattern and attempting to locate another prior pixel that matches the initial target pixel;

(e) if another matching prior pixel is located, defining another matching data string in accordance with step (c);

(f) repeating steps (d) and (e) to define all matching data strings;

(g) determining which of the matching data strings is a longest matching data string;

(h) encoding the longest matching data string as a copy token.

14. A method for compressing image data, the image data comprising an array of pixels, including target pixels and prior pixels, each prior pixel being located in a position within the array of pixels prior to the target pixels, the method comprising the steps of:

(a) traversing the prior pixels according to a predetermined non-linear traversing pattern having a beginning and an end, the beginning occurring at a first prior pixel having a predetermined location with respect to an initial target pixel, the end occurring at a final prior pixel having another predetermined location with respect to the initial target pixel;

(b) locating an initial matching prior pixel, if any, from among the prior pixels being traversed according to the non-linear predetermined traversing pattern, the initial matching prior pixel matching the initial target pixel;

(c) if an initial matching prior pixel is located, traversing, according to a linear traverse path, both the target pixels succeeding the initial target pixel and the prior pixels succeeding the initial matching prior pixel, each succeeding target pixel having a corresponding succeeding prior pixel along the linear traverse path;

(d) comparing each succeeding target pixel to the corresponding succeeding prior pixel and continuing traversing in the linear traverse path until a succeeding target pixel is located that does not match the corresponding succeeding prior pixel, thereby locating a non-matching prior pixel;

(e) defining a matching data string as a string of pixels beginning with the initial matching prior pixel and ending with the prior pixel immediately preceding the non-matching prior pixel in the array of pixels;

(f) continuing traversing the prior pixels in the non-linear traversing pattern, beginning with a prior pixel preceding the initial matching prior pixel within the non-linear traversing pattern, and attempting to locate another prior pixel that matches the initial target pixel;

(g) if another matching prior pixel is located, repeating steps (c) through (e) to define another matching data string;

(h) repeating steps (f) and (g) until reaching the final prior pixel;

(i) if only one matching data string is defined, characterizing the one matching data string as a longest matching data string;

(j) if a plurality of matching data strings are defined, determining which of the plurality of matching data strings is the longest matching data string; and

(k) encoding the longest matching data string as a copy token.

15. A method for compressing a stream of image data in a data compression system into a stream of encoded image data and for decompressing the stream of encoded image data into a decompressed image, the stream of image data comprising an array of pixels, the data compression system including a pixel pointer for indicating a target pixel being scanned, the method comprising the steps of:

(a) scanning at least one of the pixels in array of pixels to obtain prior scanned pixels, each prior scanned pixel having a location within the array of pixels;

(b) searching the prior scanned pixels for a matching data string that matches a string of pixels being scanned, including;

(1) scanning an initial target pixel, the initial target pixel having a position in the array of pixels;

(2) traversing the prior scanned pixels according to a predetermined non-linear traversing pattern;

(3) determining whether any of the prior scanned pixels being traversed matches the initial target pixel being scanned, thereby locating an initial matching prior scanned pixel;

(4) advancing the pixel pointer to a next target pixel to be scanned, the next target pixel being located at a position within the array of pixels immediately following the position of the initial target pixel;

(5) determining whether the next target pixel matches a succeeding prior scanned pixel, the succeeding prior scanned pixel having a position in the array of pixels immediately following the initial matching prior scanned pixel;

(6) advancing the pixel pointer and repeating step b(5) and thereby locating all succeeding prior scanned pixels that match the pixel indicated by the pixel pointer, until a matching prior scanned pixel is not found, thereby defining the matching data string;

(c) determining an offset representing a location, relative to the initial target pixel in the array of pixels, of the initial matching prior scanned pixel;

(d) determining a string length of the matching data string, the string length being the number of matching prior scanned pixels in the matching data string;

(e) converting the matching data string to a copy token, the copy token comprising the offset of the initial matching scanned pixel and the string length of the matching data string; and

(f) encoding the copy token.

16. The method of claim 15, further comprising the step of:

(a) subsampling the array of pixels to reduce the data in the image data stream before searching the scanned prior pixels for the matching data string.

17. The method of claim 16 wherein each pixel includes color image data, the method further comprising the step of:

(a) filtering the color image data of each pixel before subsampling the array of pixels.

18. The method of claim 17 wherein the color image data has a colorspace, the method further comprising the step of:

(a) converting the colorspace of the image data to another colorspace before filtering the color image data.

19. The method of claim 18 wherein the colorspace is a YCrCb colorspace.

20. The method of claim 15 wherein each pixel in the array of pixels has a preset tolerance for use in determining when a matching scanned pixel has been located, such that, in determining whether a prior scanned pixel matches a target pixel, the following steps are performed:

(a) comparing a target pixel being scanned to a prior scanned pixel;

(b) determining whether the prior scanned pixel is within the preset tolerance of the target pixel; and

(c) identifying the prior scanned pixel as a matching prior scanned pixel when the prior scanned pixel is within the preset tolerance of the target pixel.

21. The method of claim 15 wherein the predetermined non-linear traversing pattern has a fixed length for each individual stream of image data being compressed, the fixed length comprising an image traverse length;

and wherein the image traverse length can vary from image to image.

22. The method of claim 15 wherein the predetermined non-linear traversing pattern has a length, the length being variable during compression of a single stream of image data being compressed.

23. The method of claim 15 wherein the predetermined non-linear traversing pattern comprises a fixed pattern for each individual stream of image data being compressed, the fixed pattern being variable from image to image.

24. The method of claim 15 wherein the predetermined non-linear traversing pattern is variable during compression of a single stream of image data being compressed.

25. The method of claim 15 wherein the array of pixels has an array limit;

and wherein the predetermined non-linear traversing pattern has a plurality of segments, each of the plurality of segments corresponding to a scanned pixel, the method further comprising the step of;

(a) removing all segments from the plurality of segments that fall outside the array limit.

26. The method claim 25 wherein the predetermined non-linear traversing pattern is an empirically determined pattern, such that the empirically determined pattern causes the plurality of segments to be traversed in an empirically determined manner.

27. The method of claim 26 wherein the empirically determined pattern of the first 24 segments being traversed is as follows:

space="preserve" listing-type="tabular">______________________________________ 23 18 16 7 17 19 24 21 14 6 3 9 15 22 11 8 4 1 5 10 20 12 13 2 # ______________________________________

where "#" is a target pixel being scanned and numbers 1-24 correspond to the first 24 segments being traversed, in order from 1 to 24.

28. The method of claim 27 wherein the empirically determined pattern of the next segments being traversed is as follows:

space="preserve" listing-type="tabular">______________________________________ 46 47 48 49 50 51 52 53 54 55 56 65 45 29 30 31 32 33 34 35 36 37 57 64 44 28 . . . . . . . . . . . . . . 38 58 63 43 27 . . . . . . . . . . . . . . 39 59 62 42 26 . . . . . . . . . . . . . . 40 60 61 41 25 . . . . . . # ______________________________________

where the numbers 25-65 correspond to the next 41 segments being traversed, in order from 25-65.

29. The method of claim 26 wherein at least one of the plurality of segments in the predetermined non-linear traversing pattern is given a preferential status over the other segments in the traversing pattern, the copy token having a plurality of token positions;

and wherein the at least one segment given the preferential status is assigned an optimal token position from among the plurality of token positions within the copy token.

30. The method of claim 15 wherein the stream of image data comprises a rectangular image.

31. The method of claim 15 wherein the matching data string is encoded according to a Huffman algorithm.

32. The method of claim 15 wherein the stream of encoded image data includes tokenized data, including literal tokens, each literal token corresponding to a pixel being scanned and having no matching prior scanned pixel, and including copy tokens, each copy token corresponding to a matching data string, if any, the method further comprising the steps of:

(a) converting each pixel being scanned having no matching prior scanned pixel into a literal token;

(b) converting each matching data string, if any, into a copy token;

(c) encoding each of the literal tokens and each of the copy tokens using a Huffman compression algorithm to obtain the stream of encoded image data;

(d) transmitting the stream of encoded image data; and

(e) decoding the stream of encoded image data using a Huffman decompression algorithm to obtain a decoded stream of image data.

33. The method of claim 32, further comprising the step of:

(a) expanding the decoded stream of image data, including expanding each of the literal tokens and each of the copy tokens into pixel component values to obtain the decompressed image.

34. The method of claim 33 wherein the stream of encoded image data is decoded and expanded simultaneously.

35. The method of claim 33, further comprising the step of:

(a) filtering the pixel component values to enhance the decompressed image.

36. The method of claim 15 wherein the decompressed image is a two-dimensional image, the method further comprising the step of:

(a) reinterpolating the decompressed image, including performing a linear interpolation in both dimensions of the two-dimensional image.

37. The method of claim 20 wherein the preset tolerance is variable.

38. The method of claim 20, further comprising the step of:

(a) if the prior scanned pixel being compared is outside the preset tolerance of the target pixel being compared, continuing to perform the search of the array of pixels to determine whether another prior scanned pixel is within the preset tolerance of a pixel positioned immediately following the target pixel in the array of pixels.

39. The method of claim 33, further comprising the steps of:

(a) subsampling the stream of image data to obtain a splash image;

(b) encoding the splash image to obtain an encoded splash image;

(c) transmitting the encoded splash image;

(d) decoding the encoded splash image to obtain a decoded splash image; and

(e) displaying the decoded splash image while the stream of encoded data is decoded and expanded.

40. The method of claim 39 wherein the splash image includes a plurality of colors, the method further comprising the steps of:

(a) determining a pre-splash code representing a most common color from among the plurality of colors; and

(b) displaying the most common color as a background color for the decoded splash image.

41. A method for compressing a stream of image data in a data compression system and for decompressing the stream of image data into a decompressed image, the stream of image data comprising an array of pixels, the array of pixels being capable of being subdivided into strings incorporating at least one of the pixels from the array of pixels, the method comprising the steps of:

(a) scanning the array of pixels according to a predetermined non-linear traversing pattern to obtain prior scanned pixels;

(b) comparing pixels being scanned to the prior scanned pixels to determine whether any pixels being scanned match any of the prior scanned pixels;

(c) generating a matching data string for each string, if any, of at least one pixel being scanned that has a corresponding string of at least one prior scanned pixel that matches the pixel being scanned, each matching data string including image data corresponding to the matching prior scanned pixel;

(d) if any matching data strings are generated, converting each such matching data string into a copy token;

(e) if a pixel being scanned has no matching prior scanned pixel, converting the pixel being scanned into a literal token;

(f) encoding the copy tokens, if any, and the literal tokens to obtain an encoded token set;

(g) transmitting the encoded token set;

(h) decoding the encoded token set to obtain a decoded token set; and

(i) expanding the decoded token set to obtain the decompressed image.

42. The method of claim 41 wherein the comparing step further includes the steps of:

(a) selecting an initial pixel being scanned;

(b) traversing the prior scanned pixels according to the predetermined non-linear traversing pattern, such that the initial pixel being scanned is compared to individual prior scanned pixels according to the predetermined non-linear traversing pattern;

(c) stopping traversing the prior scanned pixels in the predetermined non-linear traversing pattern if a first matching prior scanned pixel is located that matches the initial pixel;

(d) selecting a next pixel to be scanned, the next pixel being located in a position immediately following the initial pixel in the array of pixels;

(e) comparing the next pixel to a succeeding prior scanned pixel, the succeeding prior scanned pixel being located in a position immediately following the first matching prior scanned pixel in the array of pixels;

(f) determining whether the succeeding prior scanned pixel matches the next pixel and thereby determining whether another matching prior scanned pixel exists; and

(g) repeating selecting a next pixel to be scanned and comparing such next pixel to another succeeding prior scanned pixel, until a succeeding prior scanned pixel fails to match a next pixel.

43. The method of claim 41 wherein the step of converting the matching data string into a copy token further includes the steps of:

(a) determining an offset representing a location of the first matching prior scanned pixel relative to the initial pixel within the array of pixels;

(b) determining a string length representing the number of matching prior scanned pixels determined; and

(c) coupling together the offset of the first matching prior scanned pixel and the string length to form the copy token.

44. The method of claim 41 wherein the copy tokens and literal tokens are encoded according to a Huffman algorithm.

45. The method of claim 41, further comprising the steps of:

(a) generating a Huffman tree corresponding positionally to all possible copy tokens and literal tokens;

(b) encoding the Huffman tree in a compressed format to obtain a compressed Huffman tree;

(c) transmitting the compressed Huffman tree before transmitting the encoded token set;

(d) decoding and expanding the compressed Huffman tree; and

(e) using the Huffman tree to decode the encoded token set.

46. The method of claim 41, further comprising the steps of:

(a) segmenting the encoded token set into a plurality of blocks, the plurality of blocks being decoded in succession upon being transmitted; and

(b) displaying each of the plurality of blocks as they are decoded, such that portions of the decoded image, each portion corresponding to one of the plurality of blocks, can be displayed immediately after each such portion is decoded.

47. The method of claim 41, further comprising the steps of:

(a) subsampling the stream of image data before scanning the array of pixels to reduce the data in the stream of image data; and

(b) reinterpolating the decompressed image.

48. The method of claim 41 wherein each pixel being scanned has a tolerance;

and wherein a prior scanned pixel matches a pixel being scanned if the prior scanned pixel falls within the tolerance of the pixel being scanned.

49. The method of claim 48, further comprising the step of:

(a) providing a second tolerance indicating an average quality of matching scanned pixels.

50. A data compression system for compressing a stream of image data into a stream of encoded image data and for decompressing the stream of encoded image data into a decompressed image, the stream of image data comprising an array of pixels, the data compression system including a pixel pointer for indicating a target pixel being scanned, the system comprising:

(a) a scanner for scanning at least one of the pixels in the array of pixels to obtain prior scanned pixels, each prior scanned pixel having a location within the array of pixels;

(b) means for searching the prior scanned pixels for a matching data string that matches a string of pixels being scanned, including;

(1) means for scanning an initial target pixel, the initial target pixel having a position in the array of pixels;

(2) means for traversing the prior scanned pixels using a predetermined non-linear traversing pattern;

(3) first comparing means for determining whether any of the prior scanned pixels matches the initial target pixel being scanned, thereby locating an initial matching prior scanned pixel;

(4) means for advancing the pixel pointer to a next target pixel to be scanned, the next target pixel being located at a position within the array of pixels immediately following the position of the initial target pixel;

(5) second comparing means for determining whether the next target pixel matches a succeeding prior scanned pixel, the succeeding prior scanned pixel having a position in the array of pixels immediately following the initial matching prior scanned pixel;

(6) means for advancing the pixel pointer and repeating step b(5) and for thereby locating all succeeding prior scanned pixels that match the pixel indicated by the pixel pointer, until a matching prior scanned pixel is not found, thereby defining the matching data string;

(c) means for determining an offset representing a location, relative to the initial target pixel in the array of pixels, of the initial matching prior scanned pixel;

(d) means for determining a string length of the matching data string, the string length being the number of matching prior scanned pixels in the matching data string;

(e) a converter for converting the matching data string to a copy token, the copy token comprising the offset of the initial matching prior scanned pixel and the string length of the matching data string; and

(f) an encoder for encoding the copy token.

51. The system of claim 50, further comprising:

(a) a sampling device for subsampling the array of pixels to reduce the data in the image data stream before operating the means for searching the prior scanned pixels.

52. The system of claim 51 wherein each pixel includes color image data, the system further comprising:

(a) a filter for filtering the color image data of each pixel before the sampling device subsamples the array of pixels.

53. The system of claim 52 wherein the color image data has a colorspace, the system further comprising:

(a) a converter for converting the colorspace of the image data to another colorspace before filtering the color image data.

54. The system of claim 53 wherein the colorspace is a YCrCb colorspace.

55. The system of claim 50 wherein each pixel in the array of pixels has a preset tolerance for use in determining when a matching prior scanned pixel has been located, the first and second comparing means each including:

(a) a comparator for comparing a target pixel being scanned to a prior scanned pixel;

(b) means for determining whether the prior scanned pixel is within the preset tolerance of the target pixel; and

(c) means for identifying the prior scanned pixel as a matching prior scanned pixel when the prior scanned pixel is within the preset tolerance of the target pixel.

56. The system of claim 50 wherein the predetermined non-linear traversing pattern has a fixed length for each individual stream of image data being compressed, the fixed length comprising an image traverse length;

and wherein the image traverse length can vary from image to image.

57. The system of claim 50 wherein the predetermined non-linear traversing pattern has a length, the length being variable during compression of a single stream of image data being compressed.

58. The system of claim 50 wherein the predetermined non-linear traversing pattern comprises a fixed pattern for each individual stream of image data being compressed, the fixed pattern being variable from image to image.

59. The system of claim 50 wherein the predetermined traversing pattern is variable during compression of a single stream of image data being compressed.

60. The system of claim 50 wherein the array of pixels has an array limit;

and wherein the predetermined non-linear traversing pattern includes a plurality of segments, each of the plurality of segments corresponding to a prior scanned pixel, the system further comprising;

(a) means for removing all segments from the plurality of segments that fall outside the array limit.

61. The system of claim 60 wherein the predetermined non-linear traversing pattern is an empirically determined pattern, such that the means for traversing the prior scanned pixels causes the plurality of segments to be traversed in an empirically determined manner.

62. The system of claim 61 wherein the empirically determined pattern of the first 24 segments being traversed is as follows:

space="preserve" listing-type="tabular">______________________________________ 23 18 16 7 17 19 24 21 14 6 3 9 15 22 11 8 4 1 5 10 20 12 13 2 # ______________________________________

where "#" is a target pixel being scanned and numbers 1-24 correspond to the first 24 segments being traversed, in order from 1 to 24.

63. The system of claim 62 wherein the empirically determined pattern of the next 41 segments being traversed is as follows:

space="preserve" listing-type="tabular">______________________________________ 46 47 48 49 50 51 52 53 54 55 56 65 45 29 30 31 32 33 34 35 36 37 57 64 44 28 . . . . . . . . . . . . . . 38 58 63 43 27 . . . . . . . . . . . . . . 39 59 62 42 26 . . . . . . . . . . . . . . 40 60 61 41 25 . . . . . . # ______________________________________

where the numbers 25-65 correspond to the next 41 segments being traversed, in order from 25-65.

64. The system of claim 61 wherein at least one of the plurality of segments in the empirically determined pattern has a preferential status over the other segments in the empirically determined pattern, the copy token having a plurality of token positions;

and wherein the segment given the preferential status is assigned an optimal token position from among the plurality of token positions within the copy token.

65. The system of claim 50 wherein the stream of image data comprises a rectangular image.

66. The system of claim 50 wherein the matching data string is encoded according to a Huffman algorithm.

67. The system of claim 50 wherein the stream of encoded image data includes tokenized data, including literal tokens, each literal token corresponding to a pixel being scanned having no matching prior scanned pixel, and including copy tokens, each copy token corresponding to a matching data string, if any, the system further comprising:

(a) a converter for converting each pixel being scanned that has no matching prior scanned pixel into a literal token;

(b) a converter for converting each matching data string, if any, into a copy token;

(c) an encoder for encoding each of the literal tokens and each of the copy tokens using a Huffman compression algorithm to obtain the stream of encoded image data;

(d) a transmitter for transmitting the stream of encoded image data; and

(e) a decoder for decoding the stream of encoded image data using a Huffman decompression algorithm to obtain a decoded stream of image data.

68. The system of claim 67, further comprising:

(a) means for expanding the decoded stream of image data, including means for expanding each of the literal tokens and each of the copy tokens into pixel component values to obtain the decompressed image.

69. The system of claim 68 wherein the stream of encoded image data is decoded and expanded simultaneously.

70. The system of claim 68, further comprising:

(a) a filter for filtering the pixel component values to enhance the decompressed image.

71. The system of claim 50 wherein the decompressed image is a two-dimensional image, the system further comprising:

(a) means for reinterpolating the decompressed image, including means for performing a linear interpolation in both dimensions of the two-dimensional image.

72. The system of claim 55 wherein the preset tolerance is variable.

73. The system of claim 55, further comprising:

(a) if the prior scanned pixel being compared by the comparator is outside the preset tolerance of the target pixel being compared by the comparator, means for continuing to perform the search of the array of pixels to determine whether another prior scanned pixel is within the preset tolerance of a pixel positioned immediately following the target pixel in the array of pixels.

74. The system of claim 68, further comprising:

(a) a sampler for subsampling the stream of image data to obtain a splash image;

(b) an encoder for encoding the splash image to obtain an encoded splash image;

(c) a transmitter for transmitting the encoded splash image;

(d) a decoder for decoding the encoded splash image to obtain a decoded splash image; and

(e) a display for displaying the decoded splash image while the stream of encoded data is decoded and expanded.

75. The system of claim 74 wherein the splash image includes a plurality of colors, the system further comprising:

(a) means for determining a pre-splash code representing a most common color from among the plurality of colors; and

(b) a display for displaying the most common color as a background color for the decoded splash image.

76. A system for compressing a stream of image data and for decompressing the stream of image data into a decompressed image, the stream of image data comprising an array of pixels, the array of pixels being capable of being subdivided into strings incorporating at least one of the pixels from the array of pixels, the system comprising:

(a) a scanner for scanning the array of pixels in a predetermined non-linear traversing pattern to obtain prior scanned pixels;

(b) a comparator for comparing pixels being scanned to the prior scanned pixels to determine whether any pixels being scanned match any of the prior scanned pixels;

(c) means for generating a matching data string, if any, for each string of at least one pixel being scanned that has a corresponding string of at least one prior scanned pixel that matches the pixel being scanned, each matching data string including image data corresponding to the matching prior scanned pixel;

(d) if any matching data strings are generated, a converter for converting each such matching data string into a copy token;

(e) if a pixel being scanned has no matching prior scanned pixel, a converter for converting the pixel being scanned into a literal token;

(f) an encoder for encoding the copy tokens, if any, and the literal tokens to obtain an encoded token set;

(g) a transmitter for transmitting the encoded token set;

(h) a decoder for decoding the encoded token set to obtain a decoded token set; and

(i) means for expanding the decoded token set to obtain the decompressed image.

77. The system of claim 76 wherein the comparator further includes:

(a) means for selecting an initial pixel being scanned;

(b) means for traversing the prior scanned pixels according to the predetermined non-linear traversing pattern, such that the initial pixel being scanned is compared to individual prior scanned pixels according to the predetermined non-linear traversing pattern;

(c) means for stopping traversing the prior scanned pixels in the predetermined non-linear traversing pattern if a first matching prior scanned pixel is located that matches the initial pixel;

(d) means for selecting a next pixel to be scanned, the next pixel being located in a position immediately following the initial pixel in the array of pixels;

(e) means for comparing the next pixel to a succeeding prior scanned pixel, the succeeding prior scanned pixel being located in a position immediately following the first matching scanned pixel in the array of pixels;

(f) means for determining whether the succeeding prior scanned pixel matches the next pixel and thereby determining whether another matching prior scanned pixel exists; and

(g) means for repeating selecting a next pixel to be scanned and comparing such next pixel to another succeeding prior scanned pixel, until such succeeding prior scanned pixel fails to match such next pixel.

78. The system of claim 76 wherein the converter for converting the matching data string into a copy token further includes:

(a) means for determining an offset representing a location of the first matching scanned pixel relative to the initial pixel within the array of pixels;

(b) means for determining a string length representing the number of matching scanned pixels determined; and

(c) means for coupling together the offset of the first matching scanned pixel and the string length to form the copy token.

79. The system of claim 76 wherein the copy tokens and literal tokens are encoded according to a Huffman algorithm.

80. The system of claim 76, further comprising:

(a) means for generating a Huffman tree corresponding positionally to all possible copy tokens and literal tokens;

(b) an encoder for encoding the Huffman tree in a compressed format to obtain a compressed Huffman tree;

(c) a transmitter for transmitting the compressed Huffman tree before transmitting the encoded token set;

(d) a decoder for decoding and expanding the compressed Huffman tree; and

(e) means for using the Huffman tree to decode the encoded token set.

81. The system of claim 76, further comprising:

(a) means for segmenting the encoded token set into a plurality of blocks, the plurality of blocks being decoded in succession upon being transmitted; and

(b) a display unit for displaying each of the plurality of blocks as they are decoded, such that portions of the decoded image, each portion corresponding to one of the plurality of blocks, can be displayed immediately after each such portion is decoded.

82. The system of claim 76, further comprising:

(a) a sampler for subsampling the stream of image data before scanning the array of pixels to reduce the data in the stream of image data; and

(b) means for reinterpolating the decompressed image.

83. The system of claim 76 wherein each pixel being scanned has a tolerance;

and wherein a prior scanned pixel matches a pixel being scanned if the prior scanned pixel falls within the tolerance of the pixel being scanned.

84. The system of claim 83, further comprising:

(a) means for providing a second tolerance indicating an average quality of matching scanned pixels.

85. A computer program for compressing a stream of image data into a stream of encoded image data and for decompressing the stream of encoded image data into a decompressed image, the stream of image data comprising an array of pixels, the computer program being tangibly stored on a media readable by a computer system, the computer system including a pixel pointer for indicating a target pixel being scanned, the computer program being adapted for configuring the computer system upon being read and executed by the computer system to perform the functions of:

(a) scanning at least one of the pixels in the array of pixels to obtain prior scanned pixels, each prior scanned pixel having a location within the array of pixels;

(b) searching the prior scanned pixels for a matching data string that matches a string of pixels being scanned, including;

(1) scanning an initial target pixel, the initial target pixel having a position in the array of pixels;

(2) traversing the prior scanned pixels according to a predetermined non-linear traversing pattern;

(3) determining whether any of the prior scanned pixels being traversed matches the initial target pixel being scanned, thereby locating an initial matching prior scanned pixel;

(4) advancing the pixel pointer to a next target pixel to be scanned, the next target pixel being located at a position within the array of pixels immediately following the position of the initial target pixel;

(5) determining whether the next target pixel matches a succeeding prior scanned pixel, the succeeding prior scanned pixel having a position in the array of pixels immediately following the initial matching prior scanned pixel;

(6) advancing the pixel pointer and repeating function b(5) and thereby locating all succeeding prior scanned pixels that match the pixel indicated by the pixel pointer, until a matching prior scanned pixel is not found, thereby defining the matching data string;

(c) determining an offset representing a location, relative to the initial target pixel in the array of pixels, of the initial matching prior scanned pixel;

(d) determining a string length of the matching data string, the string length being the number of matching prior scanned pixels in the matching data string;

(e) convening the matching data string to a copy token, the copy token comprising the offset of the initial matching scanned pixel and the string length of the matching data string; and

(f) encoding the copy token.

86. The computer program of claim 85, further performing the function of:

(a) subsampling the array of pixels to reduce the data in the image data stream before searching the prior scanned pixels for the matching data string.

87. The computer program of claim 85 wherein each pixel in the array of pixels has a preset tolerance for use in determining when a matching prior scanned pixel has been located, such that, in determining whether a prior scanned pixel matches a target pixel, the computer program performs the following further functions of:

(a) comparing a target pixel being scanned to a prior scanned pixel;

(b) determining whether the prior scanned pixel is within the preset tolerance of the target pixel; and

(c) identifying the prior scanned pixel as a matching prior scanned pixel when the prior scanned pixel is within the preset tolerance of the target pixel.

88. The computer program of claim 85 wherein the predetermined non-linear traversing pattern has a fixed length for each individual stream of image data being compressed, the fixed length comprising an image traverse length;

and wherein the image traverse length can vary from image to image.

89. The computer program of claim 85 wherein the array of pixels has an array limit;

and wherein the predetermined non-linear traversing pattern has a plurality of segments, each of the plurality of segments corresponding to a prior scanned pixel, the computer program further performing the following function;

(a) removing all segments from the plurality of segments that fall outside the array limit.

90. The computer program of claim 85 wherein the matching data string is encoded according to a Huffman algorithm.

91. The computer program of claim 85, wherein the stream of encoded image data includes tokenized data, including literal tokens, each of the literal tokens corresponding to a pixel being scanned and having no matching prior scanned pixel, and including copy tokens, each copy token corresponding to a matching data string, if any, the computer program further performing the following functions:

(a) converting each pixel being scanned that has no matching prior scanned pixel into a literal token;

(b) converting each matching data string, if any, into a copy token;

(c) encoding each of the literal tokens and each of the copy tokens using a Huffman compression algorithm to obtain the stream of encoded image data;

(d) transmitting the stream of encoded image data; and

(e) decoding the stream of encoded image data using a Huffman decompression algorithm to obtain a decoded stream of image data.

92. The computer program of claim 91, further performing the function of:

(a) expanding the decoded stream of image data, including expanding each of the literal tokens and each of the copy tokens into pixel component values to obtain the decompressed image.

93. The computer program of claim 92, wherein the stream of encoded image data is decoded and expanded simultaneously.

94. The computer program of claim 92, further performing the functions of:

(a) subsampling the stream of image data to obtain a splash image;

(b) encoding the splash image to obtain an encoded splash image;

(c) transmitting the encoded splash image;

(d) decoding the encoded splash image to obtain a decoded splash image; and

(e) displaying the decoded splash image while the stream of encoded data is decoded and expanded.

95. A computer program for compressing a stream of image data and for decompressing the stream of image data into a decompressed image, the stream of image data comprising an array of pixels, the array of pixels being capable of being subdivided into strings incorporating at least one of the pixels from the array of pixels, the computer program being tangibly stored on a media readable by a computer system, the computer program being adapted for configuring the computer system upon being read and executed by the computer system to perform the functions of:

(a) scanning the array of pixels according to a predetermined non-linear traversing pattern to obtain prior scanned pixels;

(b) comparing pixels being scanned to the prior scanned pixels to determine whether any pixels being scanned match any of the prior scanned pixels;

(c) generating a matching data string for each string of at least one pixel being scanned that has a corresponding string of at least one prior scanned pixel that matches the pixel being scanned, each matching data string including image data corresponding to the matching prior scanned pixel;

(d) if any matching data strings are generated, converting each such matching data string into a copy token;

(e) if a pixel being scanned has no matching prior scanned pixel, converting the pixel being scanned into a literal token;

(f) encoding the copy tokens, if any, and the literal tokens to obtain an encoded token set;

(g) transmitting the encoded token set;

(h) decoding the encoded token set to obtain a decoded token set; and

(i) expanding the decoded token set to obtain the decompressed image.

96. The computer program of claim 95 wherein the function of comparing pixels being scanned further includes the following functions:

(a) selecting an initial pixel being scanned;

(b) traversing the prior scanned pixels according to the predetermined non-linear traversing pattern, such that the initial pixel being scanned is compared to individual prior scanned pixels according to the predetermined non-linear traversing pattern;

(c) stopping traversing the prior scanned pixels in the predetermined non-linear traversing pattern if a first matching prior scanned pixel is located that matches the initial pixel;

(d) selecting a next pixel to be scanned, the next pixel being located in a position immediately following the initial pixel in the array of pixels;

(e) comparing the next pixel to a succeeding prior scanned pixel, the succeeding prior scanned pixel being located in a position immediately following the first matching prior scanned pixel in the array of pixels;

(f) determining whether the succeeding prior scanned pixel matches the next pixel and thereby determining whether another matching prior scanned pixel exists; and

(g) repeating selecting a next pixel to be scanned and comparing such next pixel to another succeeding prior scanned pixel, until a succeeding prior scanned pixel fails to match a next pixel.

97. The computer program of claim 96 wherein the function of converting the matching data string into a copy token further includes the functions of:

(a) determining an offset representing a location of the first matching scanned pixel relative to the initial pixel within the array of pixels;

(b) determining a string length representing the number of matching prior scanned pixels determined; and

(c) coupling together the offset of the first matching prior scanned pixel and the string length to form the copy token.

98. The computer program of claim 95, further performing the functions of:

(a) generating a Huffman tree corresponding positionally to all possible copy tokens and literal tokens;

(b) encoding the Huffman tree in a compressed format to obtain a compressed Huffman tree;

(c) transmitting the compressed Huffman tree before transmitting the encoded token set;

(d) decoding and expanding the compressed Huffman tree; and

(e) using the Huffman tree to decode the encoded token set.

99. The computer program of claim 95, further performing the functions of:

(a) segmenting the encoded token set into a plurality of blocks, the plurality of blocks being decoded in succession upon being transmitted; and

(b) displaying each of the plurality of blocks as they are decoded, such that portions of the decoded image, each portion corresponding to one of the plurality of blocks, can be displayed immediately after each such portion is decoded.

100. The computer program of claim 95, wherein each pixel being scanned has a tolerance;

and wherein a prior scanned pixel matches a pixel being scanned if the prior scanned pixel falls within the tolerance of the pixel being scanned.

101. A method for compressing an incoming data stream, the incoming data stream comprising a plurality of incoming data segments, a group of two or more of the plurality of incoming data segments comprising an incoming data string, the method comprising the steps of:

(a) reading the incoming data stream to obtain prior data, the prior data including a plurality of prior data segments, a group of two or more of the plurality of prior data segments comprising a prior data string;

(b) searching the prior data in a predetermined non-linear traversing pattern for longest matching prior data strings, each longest matching prior data string comprising a prior data string and matching an incoming data string from the incoming data stream;

(c) if any longest matching prior data strings are found in the prior data, compressing the longest matching prior data strings to obtain compressed strings and encoding the compressed strings as copy tokens;

(d) for any incoming data segment having no matching prior data segment, encoding such incoming data segment as a literal token; and

(e) outputting the copy tokens, if any, and the literal tokens.

102. The method of claim 101, wherein the incoming data stream comprises an image having a plurality of pixels;

wherein the plurality of prior data segments comprise a plurality of prior pixels in the image and the plurality of incoming segments comprise a plurality of target pixels in the image; and

wherein the predetermined non-linear traverse pattern is a variable pattern determined empirically based on the frequency of matches between prior pixels and a selected target pixel.

103. The method of claim 101, wherein the target pixels have a tolerance level;

and wherein a string of prior pixels is considered to match a string of target pixels if the string of prior pixels falls within the tolerance level of the string of target pixels.

104. A system for compressing an incoming data stream, the incoming data stream comprising a plurality of incoming data segments, a group of two or more of the plurality of incoming data segments comprising an incoming data string, the system comprising:

(a) means for reading the incoming data stream to obtain prior data, the prior data including a plurality of prior data segments, a group of two or more of the plurality of prior data segments comprising a prior data string;

(b) means for searching the prior data in a predetermined non-linear traversing pattern for longest matching prior data strings, each longest matching prior data string comprising a prior data string and matching an incoming data string from the incoming data stream;

(c) if any longest matching prior data strings are found in the prior data, a compressor for compressing the longest matching prior data strings to obtain compressed strings and an encoder for encoding the compressed strings as copy tokens;

(d) for any incoming data segment having no matching prior data segment, an encoder for encoding such incoming data segment as a literal token; and

(e) a port for outputting the copy tokens, if any, and the literal tokens.

105. A method for compressing data, the data including a plurality of data segments having an order, the plurality of data segments including target segments and prior segments, the prior segments preceding the target segments within the order of the plurality of data segments, the method comprising the steps of:

(a) selecting an initial target segment;

(b) traversing the prior segments according to a predetermined non-linear traversing pattern; and

(c) locating a longest matching string of prior segments that matches a string of target segments, the string of target segments commencing at the initial target segment, the string of prior segments having an initial matching prior segment lying within the predetermined non-linear traversing pattern.

106. The method of claim 105, wherein the locating step includes the steps of:

(a) traversing the prior segments, commencing at the initial matching prior segment, in a first linear traverse path;

(b) traversing the target segments, commencing at the initial target segment, in a second linear traverse path, each target segment along the second linear traverse path having a corresponding prior segment along the first linear traverse path;

(c) comparing each target segment lying along the second linear traverse path to the corresponding prior segment lying along the first linear traverse path to determine whether each such target segment matches the corresponding prior segment; and

(d) stopping traversing the prior segments and target segments if a target segment fails to match the corresponding prior segment, the number of matching prior segments commencing at the initial matching prior segment comprising a first matching string having a first matching string length.

107. The method of claim 106 wherein the locating step further includes the steps of:

(a) after the stopping step, continuing traversing in the predetermine non-linear traversing pattern the prior segment preceding the initial matching prior segment;

(b) locating a next matching prior segment, if any, within the non-linear traversing pattern, that matches the initial target segment;

(c) traversing the prior segments, commencing at the next matching prior segment, in a third linear traverse path;

(d) traversing the target segments, commencing at the initial target segment, in the second linear traverse path, each target segment along the second linear traverse path having a corresponding prior segment along the third linear traverse path;

(e) comparing each target segment lying along the second linear traverse path to the corresponding prior segment lying along the third linear traverse path to determine whether each such target segment matches the corresponding prior segment;

(f) stopping traversing the prior segments and target segments if a target segment fails to match the corresponding prior segment, the number of matching prior segments commencing at the next matching prior segment comprising a second matching string having a second matching string length;

(g) comparing the first matching string length of the first matching string to the second matching string length of the second matching string to determine which is longer; and

(h) defining the matching string having the longer length as the longest matching string of prior segments.

108. The method of claim 105, wherein the step of locating a longest matching string includes applying a tolerance level to the prior segments to determine whether prior segments match target segments.

109. The method of claim 105, wherein the predetermined non-linear traversing pattern has a fixed length.

110. The method of claim 105, wherein the predetermined non-linear traversing pattern has a fixed pattern;

and wherein the first 24 data segments traversed by the predetermined non-linear traversing pattern are as follows;

space="preserve" listing-type="tabular">______________________________________ 23 18 16 7 17 19 24 21 14 6 3 9 15 22 11 8 4 1 5 10 20 12 13 2 # ______________________________________

where "#" represents the initial target segment and the numbers 1-24 represent the first 24 data segments traversed, in order from 1 to 24.

111. The method of claim 105, wherein the data comprises image data and the plurality of data segments comprise a plurality of pixels.

112. A system for compressing data, the data including a plurality of segments having an order, the plurality of segments including target segments and prior segments, the prior segments preceding the target segments within the order of the plurality of segments, the system comprising:

(a) means for selecting an initial target segment;

(b) means for traversing the prior segments according to a predetermined non-linear traversing pattern; and

(c) means for locating a longest matching string of prior segments that matches a string of target segments, the string of target segments commencing at the initial target segment, the string of prior segments having an initial matching prior segment lying within the predetermined non-linear traversing pattern.

113. The system of claim 112, wherein the means for locating includes:

(a) means for traversing the prior segments, commencing at the initial matching prior segment, in a first linear traverse path;

(b) means for traversing the target segments, commencing at the initial target segment, in a second linear traverse path, each target segment along the second linear traverse path having a corresponding prior segment along the first linear traverse path;

(c) means for comparing each target segment lying along the second linear traverse path to the corresponding prior segment lying along the first linear traverse path to determine whether each such target segment matches the corresponding prior segment; and

(d) means for stopping traversing the prior segments and target segments if a target segment fails to match the corresponding prior segment, the number of matching prior segments commencing at the initial matching prior segment comprising a first matching string having a first matching string length.

114. The system of claim 113, wherein the means for locating further includes:

(a) after operation of the stopping means, means for continuing traversing in the predetermined non-linear traversing pattern the prior segments preceding the initial matching prior segment;

(b) means for locating a next matching prior segment, if any, within the non-linear traversing pattern, that matches the initial target segment;

(c) means for traversing the prior segments, commencing at the next matching prior segment, in a third linear traverse path;

(d) means for traversing the target segments, commencing at the initial target segment, in the second linear traverse path, each target segment along the second linear traverse path having a corresponding prior segment along the third linear traverse path;

(e) means for comparing each target segment lying along the second linear traverse path to the corresponding prior segment lying along the third linear traverse path to determine whether each such target segment matches the corresponding prior segment;

(f) means for stopping traversing the prior segments and target segments if a target segment fails to match the corresponding prior segment, the number of matching prior segments commencing at the next matching prior segment comprising a second matching string having a second matching string length;

(g) means for comparing the first matching string length of the first matching string to the second matching string length of the second matching string to determine which is longer; and

(h) means for defining the matching string having the longer length as the longest matching string of prior segments.

115. The system of claim 112 wherein the means for locating a longest matching string includes means for applying a tolerance level to the prior segments to determine whether prior segments match target segments.

116. The system of claim 112 wherein the predetermined non-linear traversing pattern has a fixed length.

117. The system of claim 112 wherein the predetermined non-linear traversing pattern has a fixed pattern, and wherein the first 24 data segments traversed by the predetermined non-linear traversing pattern are as follows:

space="preserve" listing-type="tabular">______________________________________ 23 18 16 7 17 19 24 21 14 6 3 9 15 22 11 8 4 1 5 10 20 12 13 2 # ______________________________________

where "#" represents the initial target segment and the numbers 1-24 represent the first 24 data segments traversed, in order from 1 to 24.

118. The system of claim 112 wherein the data comprises image data and the plurality of data segments comprise a plurality of pixels.

119. A computer program for compressing data, the data including a plurality of segments having an order, the plurality of segments including target segments and prior segments, the prior segments preceding the target segments within the order of the plurality of segments, the computer program being tangibly stored on a media readable by a computer system, the computer program being adapted for configuring the computer system upon being read and executed by the computer system to perform the functions of:

(a) selecting an initial target segment;

(b) traversing the prior segments according to a predetermined non-linear traversing pattern; and

(c) locating a longest matching string of prior segments that matches a string of target segments, the string of target segments commencing at the initial target segment, the string of prior segments having an initial matching prior segment lying within the predetermined non-linear traversing pattern.

120. The computer program of claim 119, wherein the locating function includes:

(a) traversing the prior segments, commencing at the initial matching prior segment, in a first linear traverse path;

(b) traversing the target segments, commencing at the initial target segment, in a second linear traverse path, each target segment along the second linear traverse path having a corresponding prior segment along the first linear traverse path;

(c) comparing each target segment lying along the second linear traverse path to the corresponding prior segment lying along the first linear traverse path to determine whether each such target segment matches the corresponding prior segment; and

(d) stopping traversing the prior segments and target segments if a target segment fails to match the corresponding prior segment, the number of matching prior segments commencing at the initial matching prior segment comprising a first matching string having a first matching string length.

121. The computer program of claim 120, wherein the locating function further includes:

(a) after the stopping function, continuing traversing in the predetermined non-linear traversing pattern the prior segment preceding the initial matching prior segment;

(b) locating a next matching prior segment, if any, within the non-linear traversing pattern, that matches the initial target segment;

(c) traversing the prior segments, commencing at the next matching prior segment, in a third linear traverse path;

(d) traversing the target segments, commencing at the initial target segment, in the second linear traverse path, each target segment along the second linear traverse path having a corresponding prior segment along the third linear traverse path;

(e) comparing each target segment lying along the second linear traverse path to the corresponding prior segment lying along the third linear traverse path to determine whether each such target segment matches the corresponding prior segment;

(f) stopping traversing the prior segments and target segments if a target segment fails to match the corresponding prior segment, the number of matching prior segments commencing at the next matching prior segment comprising a second matching string having a second matching string length;

(g) comparing the first matching string length of the first matching string to the second matching string length of the second matching string to determine which is longer; and

(h) defining the matching string having the longer length as the longest matching string of prior segments.