Image data encoding/decoding method and apparatus configured to compress both natural gray scale images and binary images
First Claim
1. An image data encoding/decoding apparatus, comprising:
- first data dividing means for dividing input image data into m- by n-pixel blocks each with a predetermined number of bits, m and n each being an integral multiple of 2;
first data encoding means for encoding, according to frequency information included in said input image data, each of said m- by n-pixel blocks into a first data block including a plurality of frequency data elements;
second data encoding means for encoding said each of said m- by n-pixel blocks into a second data block that represents said image data in fewer bits than said predetermined number of bits for each m- by n-pixel block, elements of said second data block includingan image density characterizing a pixel image density value common to at least two pixels in a m- by n-pixel block being encoded by said second data encoding means,locations of pixels having said image density, anda flag for specifying an image type;
first image type determining means for determining whether a number of different image density values, which pertain to pixels included in each of said m- by n-pixel blocks, is equal to a first predetermined value; and
first data selecting means for selecting said first data block from said first data encoding means when said first image type determining means determines that the number of said different image density values of said m- by n-pixel block is different from said first predetermined value and said second data block from said second data encoding means when said first image type determining means determines that the number of said different image density values of said m- by n-pixel block is equal to said first predetermined value.
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Abstract
Image data encoding/decoding method and apparatus uses a first data divider for dividing image data into--by n-pixel blocks, two data encoders for encoding an--by n-pixel block into a first data block including frequency data elements and into a second data block including an image density, locations of pixels, and a flag, respectively. A first image type determiner is also included for determining a number of different image density values included in the--by n-pixel block, as is a first data selector for selecting the first data block when the first image type determiner determines that the--by n-pixel block includes a number of different image density values different from a first predetermined value and the second data block when the first image type determiner determines that the--by n-pixel block includes a first predetermined number of the different image density values. Two data decoders are included for decoding the first data block into a block substantially similar to the block previously divided by the first data divider and the second data block into a block substantially similar to the block previously divided by the first data divider, respectively. A second image type determiner is used for determining the flag. A second data selector selects the block obtained by decoding the first data block when the flag is different from a second predetermined value and the block obtained by decoding the second data block when the flag is equal to the second predetermined value.
50 Citations
64 Claims
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1. An image data encoding/decoding apparatus, comprising:
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first data dividing means for dividing input image data into m- by n-pixel blocks each with a predetermined number of bits, m and n each being an integral multiple of 2; first data encoding means for encoding, according to frequency information included in said input image data, each of said m- by n-pixel blocks into a first data block including a plurality of frequency data elements; second data encoding means for encoding said each of said m- by n-pixel blocks into a second data block that represents said image data in fewer bits than said predetermined number of bits for each m- by n-pixel block, elements of said second data block including an image density characterizing a pixel image density value common to at least two pixels in a m- by n-pixel block being encoded by said second data encoding means, locations of pixels having said image density, and a flag for specifying an image type; first image type determining means for determining whether a number of different image density values, which pertain to pixels included in each of said m- by n-pixel blocks, is equal to a first predetermined value; and first data selecting means for selecting said first data block from said first data encoding means when said first image type determining means determines that the number of said different image density values of said m- by n-pixel block is different from said first predetermined value and said second data block from said second data encoding means when said first image type determining means determines that the number of said different image density values of said m- by n-pixel block is equal to said first predetermined value. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. An image data encoding/decoding apparatus, comprising:
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first data dividing means for dividing input image data into m- by n-pixel blocks each with a predetermined number of bits, m and n each being an integer; first data encoding means for encoding, according to frequency information included in said input image data, each of said m- by n-pixel blocks into a first data block including a plurality of frequency data elements; second data encoding means for encoding said each of said m- by n-pixel blocks into a second data block that represents said image data in fewer bits than said predetermined number of bits for each m- by n-pixel block elements of said second data block including an image density characterizing a pixel image density value common to at least two pixels in an m- by n-pixel block being encoded by said second data encoding means, locations of pixels having said image density, and a flag for specifying an image type; first image type determining means for determining as to whether a number of different image density values, which pertain to pixels included in each of said m- by n-pixel blocks, is equal to a first predetermined value; first data selecting means for selecting said first data block from said first data encoding means when said first image type determining means determines that the number of said different image density values of said m- by n-pixel block is different from said first predetermined value and said second data block from said second data encoding means when said first image type determining means determines that the number of said different image density values of said m- by n-pixel block is equal to said first predetermined value; first data decoding means for decoding said first data block into an m- by n-pixel block which is substantially similar to said m- by n-pixel block previously divided by said first data dividing means; second data decoding means for decoding said second data block into an m- by n-pixel block which is substantially similar to said m- by n-pixel block previously divided by said first data dividing means; second image type determining means for determining whether said flag data element is equal to a second predetermined value; and second data selecting means for selecting said m- by n-pixel block from said first data decoding means when said second image type determining means determines that said flag data element is different from said second predetermined value and said m- by n-pixel block from said second data decoding means when said second image type determining means determines that said flag data element is equal to said second predetermined value. - View Dependent Claims (12, 13, 14, 15, 16)
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17. An image data encoding/decoding apparatus, comprising:
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first data dividing means for dividing input image data into m- by n-pixel blocks each with a predetermined number of bits, m and n each being an integer; first data encoding means for encoding, according to frequency information included in said input image data, each of said m- by n-pixel blocks into a first data block including a plurality of sub-band data elements; second data encoding means for encoding said each of said m- by n-pixel blocks into a second data block that represents said image data in fewer bits than said predetermined number of bits for each m- by n-pixel block elements of said second data block including an image density characterizing a pixel image density value common to at least two pixels in a m- by n-pixel block being encoded by said second data encoding means, and locations of pixels having said image density; first image type determining means for determining whether a number of different image density values, which pertain to pixels included in each of said m- by n-pixel blocks, is equal to a first predetermined value; flag generating means for generating a flag data element for specifying one of image types which are an m- by n-pixel block determined to have the number of said different image density values of said m- by n-pixel block being different from said first predetermined value by said first image type determining means, and an m- by n-pixel block determined to have the number of said different image density values of said m- by n-pixel block being equal to said first predetermined value, said flag data element being used to select one of blocks based on said first data block encoded by said first data encoding means and said second data block encoded by said second data encoding means; and compressing means for compressing said first data block encoded by said first data encoding means, said second data block encoded by said second data encoding means, and said flag data element generated by said flag generating means. - View Dependent Claims (18, 19, 20, 21)
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22. An image data encoding/decoding apparatus, comprising:
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first data dividing means for dividing input image data into m- by n-pixel blocks each with a predetermined number of bits, m and n each being an integer; first data encoding means for encoding, according to frequency information included in said input image data, each of said m- by n-pixel blocks into a first data block including a plurality of sub-band data elements; second data encoding means for encoding said each of said m- by n-pixel blocks into a second data block that represents said image data in fewer bits than said predetermined number of bits for each m- by n-pixel block, elements of said second data block including an image density characterizing a pixel image density value common to at least two pixels in a m- by n-pixel block being encoded by said second data encoding means, and locations of pixels having said image density; first image type determining means for determining whether a number of different image density values, which pertain to pixels included in each of said m- by n-pixel blocks, is equal to a first predetermined value; flag generating means for generating a flag data element for specifying one of image types which are an m- by n-pixel block determined to have the number of said different image density values of said m- by n-pixel block being different from said first predetermined value by said first image type determining means, and an m- by n-pixel block determined to have the number of said different image density values of said m- by n-pixel block being equal to said first predetermined value, said flag data element being used to select one of blocks based on said first data block encoded by said first data encoding means and said second data block encoded by said second data encoding means; first data decoding means for decoding said first data block into an m- by n-pixel block which is substantially similar to said m- by n-pixel block previously divided by said first data dividing means; second data decoding means for decoding said second data block into an m- by n-pixel block which is substantially similar to said m- by n-pixel block previously divided by said first data dividing means; second image type determining means for determining whether said flag data element is equal to a second predetermined value; and data selecting means for selecting one of said m- by n-pixel block from said first data decoding means and said m- by n-pixel block from said second data decoding means in accordance with said flag data element. - View Dependent Claims (23, 24, 25, 26)
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27. An image data encoding/decoding apparatus, comprising:
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a first data divider configured to input image data into m- by n-pixel blocks each with a predetermined number of bits, m and n each being an integer; a first data encoder configured to encode, according to frequency information included in said input image data, each of said m- by n-pixel blocks into a first data block including a plurality of frequency data elements; a second data encoder configured to encode said each of said m- by n-pixel blocks into a second data block that represents said image data in fewer bits than said predetermined number of bits for each m- by n-pixel block, elements of said second data block including an image density characterizing a pixel image density value common to at least two pixels in a m- by n-pixel block being encoded by said second data encoder, locations of pixels having said image density, and a flag data element for specifying an image type; a first image type determiner configured to determine whether a number of different image density values, which pertain to pixels included in each of said m- by n-pixel blocks, is equal to a first predetermined value; and a first data selector configured to select said first data block from said first data encoder when said first image type determiner determines that the number of said different image density values of said m- by n-pixel block is different from said first predetermined value and said second data block from said second data encoder when said first image type determiner determines that the number of said different image density values of said m- by n-pixel block is equal to said first predetermined value. - View Dependent Claims (28, 29, 30, 31, 32, 33, 34, 35, 36)
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37. An image data encoding/decoding apparatus, comprising:
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a first data divider configured to divide input image data into m- by n-pixel blocks each with a predetermined number of bits, m and n each being an integer; a first data encoder configured to encode, according to frequency information included in said input image data, each of said m- by n-pixel blocks into a first data block including a plurality of frequency data elements; a second data encoder configured to encode said each of said m- by n-pixel blocks into a second data block that represents said image data in fewer bits than said predetermined number of bits for each m- by n-pixel block, elements of said second data block including an image density characterizing a pixel image density value common to at least two pixels in a m- by n-pixel block being encoded by said second data encoder, locations of pixels having said image density, and a flag data element for specifying an image type; a first image type determiner configured to determine whether a number of different image density values, which pertain to pixels included in each of said m- by n-pixel blocks, is equal to a first predetermined value; a first data selector configured to select said first data block from said first data encoder when said first image type determiner determines that the number of said different image density values of said m- by n-pixel block is different from said first predetermined value and said second data block from said second data encoder when said first image type determiner determines that the number of said different image density values of said m- by n-pixel block is equal to said first predetermined value; a first data decoder configured to decode said first data block into an m- by n-pixel block which is substantially similar to said m- by n-pixel block previously divided by said first data divider; a second data decoder configured to decode said second data block into an m- by n-pixel block which is substantially similar to said m- by n-pixel block previously divided by said first data divider; a second image type determiner configured to determine whether said flag data element is equal to a second predetermined value; and a second data selector configured to select said m- by n-pixel block from said first data decoder when said second image type determiner determines that said flag data element is different from said second predetermined value and said m- by n-pixel block from said second data decoder when said second image type determiner determines that said flag data element is equal to said second predetermined value. - View Dependent Claims (38, 39, 40, 41, 42)
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43. An image data encoding/decoding apparatus, comprising:
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a first data divider configured to divide input image data into m- by n-pixel blocks each with a predetermined number of bits, m and n being an integer; a first data encoder configured to encode, according to frequency information included in said input image data, each of said m- by n-pixel blocks into a first data block including a plurality of sub-band data elements; a second data encoder configured to encode said each of said m- by n-pixel blocks into a second data block that represents said image data in fewer bits than said m- by n-pixel block, elements of said data block including an image density characterizing a pixel image density value common to at least two pixels in a m- by n-pixel block being encoded by said second data encoder and locations of pixels having said image density; a first image type determiner configured to determine whether a number of different image density values, which pertain to pixels included in each of said m- by n-pixel blocks, is equal to a first predetermined value; a flag generator configured to generate a flag data element for specifying one of image types which are an m- by n-pixel block determined to have the number of said different image density values of said m- by n-pixel block being different from said first predetermined value by said first image type determiner, and an m- by n-pixel block determined to have the number of said different image density values of said m- by n-pixel block being equal to said first predetermined value, said flag data element being used to select one of blocks based on said first data block encoded by said first data encoder and said second data block encoded by said second data encoder; and a compressor configured to compress said first data block encoded by said first data encoder, said second data block encoded by said second data encoder, and said flag data element generated by said flag generator. - View Dependent Claims (44, 45, 46, 47)
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48. An image data encoding/decoding apparatus, comprising:
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a first data divider configured to divide input image data into m- by n-pixel blocks each with a predetermined number of bits, m and n each being an integer; a first data encoder configured to encode, according to frequency information included in said input image data, each of said m- by n-pixel blocks into a first data block including a plurality of sub-band data elements; a second data encoder configured to encode said each of said m- by n-pixel blocks into a second data block that represents said image data in fewer bits than said predetermined number of bits for each m- by n-pixel block, elements of said data block including an image density characterizing a pixel image density value common to at least two pixels in a m- by n-pixel block being encoded by said second data encoder and locations of pixels having said image density; a first image type determiner configured to determine whether a number of different image density values, which pertain to pixels included in each of said m- by n-pixel blocks, is equal to a first predetermined value; a flag generator configured to generate a flag data element for specifying one of image types which are an m- by n-pixel block determined as that the number of said different image density values of said m- by n-pixel block being different from said first predetermined value by said first image type determiner, and an m- by n-pixel block determined to have the number of said different image density values of said m- by n-pixel block being equal to said first predetermined value, said flag data element being used to select one of blocks based on said first data block encoded by said first data encoder and said second data block encoded by said second data encoder; a first data decoder configured to decode said first data block into an m- by n-pixel block which is substantially similar to said m- by n-pixel block previously divided by said first data divider; a second data decoder configured to decode said second data block into an m- by n-pixel block which is substantially similar to said m- by n-pixel block previously divided by said first data divider; a second image type determiner configured to determine whether said flag data element is equal to a second predetermined value; and a data selector configured to select one of said m- by n-pixel block from said first data decoder and said m- by n-pixel block from said second data decoder in accordance with said flag data element. - View Dependent Claims (49, 50, 51, 52)
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53. A method for encoding and decoding image data comprising the steps of:
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dividing input image data into m-by-n pixel blocks each with a predetermined number of bits, m and n each being an integer; encoding, according to frequency information included in said input image data, each of said m-by n-pixel blocks into a first data block including a plurality of frequency data elements; encoding said each of said m- by n-pixel blocks into a second data block that represents said image data in fewer than said predetermined number of bits elements of said second data block including an image density characterizing a pixel image density value common to at least two pixels of a m- by n-pixel block that is encoded into the second data block, locations of pixels having said image density, and a flag for specifying an image type; determining whether a number of different image density values, which pertain to pixels included in each of said by n-pixel blocks, is equal to a first predetermined value; and selecting said first data block when it is determined in said determining step that the number of said different image density values of respective of the m- by n-pixel block is different from said predetermined value and said second data block when it is determined that the number of said different image density values of respective of said m- by n-pixel blocks is equal to said first predetermined value.
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54. A method for encoding and decoding image data, comprising the steps of:
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dividing input image data into m- by n-pixel blocks each with a predetermined number of bits, m and n each being an integer; encoding, according to frequency information included in said input image data, each of said m- by n-pixel blocks into a first data block including a plurality of frequency data elements; encoding said each of said m- by n-pixel blocks into a second data block that represents said image data in fewer bits than said predetermined number of bits, elements of said second data block including an image density characterizing a pixel image density value common to at least two pixels of a m- by n-pixel block that is encoded into the second data block, locations of pixels having said image density, and a flag for specifying an image type; determining whether a number of different image density values, which pertain to pixels included in each of said m- by n-pixel blocks, is equal to a first predetermined value; selecting said first data block when it is determined that the number of said different image density values of said first data block is different from said first predetermined value and said second data block when it is determined that the number of said different image density values of said second data block is equal to said first predetermined value; decoding said first data block into a first decoded m- by n-pixel block which is substantially similar to said m- by n-pixel block previously divided; decoding said second data block into a second decoded m- by n-pixel block which is substantially similar to the m- by n-pixel block previously divided; determining whether said flag data element is equal to a second predetermined value; and selecting said first decoded m- by n-pixel data block after being decoded in said step of decoding said first data block, when it is determined that said flag element is different from said second predetermined value and selecting said second decoded m- by n-pixel data block after performing said step of decoding said second data block when it is determined that said flag data element is equal to said second predetermined value.
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55. A method for encoding and decoding image data, comprising the steps of:
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dividing input image data into m- by n-pixel blocks each with a predetermined number of bits, m and n each being an integer; encoding, according to frequency information included in said input image data, each of said m- by n-pixel blocks into a first data block including a plurality of sub-band data elements; encoding said each of said m- by n-pixel blocks into a second data block that represents said image data in fewer bits than said predetermined number of bits for each m- by n-pixel block, elements of said second data block including an image density characterizing a pixel image density value common to at least two pixels of a m- by n-pixel block that is encoded into the second data block, and locations of pixels having said image density; determining whether a number of different image density values, which pertain to pixels included in each of said m- by n-pixel blocks, is equal to a first predetermined value; generating a flag data element for specifying one of image types which are when an m- by n-pixel block is determined to have the number of said different image density values of said m- by n-pixel block being different from said first predetermined value, and when the m- by n-pixel block is determined to have the number of said different image density values of said m- by n-pixel block being equal to said first predetermined value, and using said flag data element to select one of blocks based on said first data block, and blocks based on said second data block; and compressing said first data block and said second data block and generating said flag data element.
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56. A method for encoding and decoding image data, comprising the steps of:
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dividing input image data into m- by n-pixel blocks each with a predetermined number of bits, m and n each being an integer; encoding, according to frequency information included in said image data, each of said m- by n-pixel blocks into a first data block including a plurality of sub-band data elements; encoding said each of said m- by n-pixel blocks into a second data block that represents said image data in fewer bits than said predetermined number of bits, elements of said second data block including an image density characterizing a pixel image density value common to at least two pixels of a m- by n-pixel block that is encoded into the second data block, and locations of pixels having said image density; determining whether a number of different image density values, which pertain to pixels included in each of said m- by n-pixel blocks, is equal to a first predetermined value; generating a flag data element for specifying one of image types which are when an m- by n-pixel block is determined to have the number of said different image density values of said m- by n-pixel block being different from said first predetermined value, and when the m- by n-pixel block is determined to have the number of said different image density values of said m- by n-pixel block being equal to said first predetermined value, using said flag data element to select one of blocks based on said first data block, and blocks based on said second data block; decoding said first data block into a first decoded m- by n-pixel block which is substantially similar to said m- by n-pixel block previously divided; decoding said second data block into a second decoded m- by n-pixel block which is substantially similar to said mn- by n-pixel block previously divided; determining whether said flag data element is equal to a second predetermined value; and selecting one of said first decoded m- by n-pixel block and said second decoded m- by n-pixel block in accordance with said flag data element.
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57. A computer product having computer readable instructions encoded therein for implementing an image data encoding/decoding apparatus which has a processor for executing said computer readable instructions, said computer program product, when said computer readable instructions are executed by said processor, comprising:
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first data dividing means for dividing input image data into m- by n-pixel blocks each with a predetermined number of bits, m and n each being an integral multiple of 2; first data encoding means for encoding, according to frequency information included in said input image data, each of said m- by n-pixel blocks into a first data block including a plurality of frequency data elements; second data encoding means for encoding said each of said m- by n-pixel blocks into a second data block that represents said image data in fewer bits than said predetermined number of bits for each m- by n-pixel block, elements of said second data block, including an image density characterizing a pixel image density value common to at least two pixels in a m- by n-pixel block being encoded by said second data encoding means, locations of pixels having said image density, and a flag for specifying an image type; first image type determining means for determining whether a number of different image density values, which pertain to pixels included in each of said m- by n-pixel blocks, is equal to a first predetermined value; and first data selecting means for selecting said first data block from said first data encoding means when said first image type determining means determines that the number of said different image density values of said m- by n-pixel block is different from said first predetermined value and said second data block from said second data encoding means when said first image type determining means determines that the number of said different image density values of said m- by n-pixel block is equal to said first predetermined value.
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58. A computer product having computer readable instructions encoded therein for implementing an image data encoding/decoding apparatus which has a processor for executing said computer readable instructions, said computer program product, when said computer readable instructions are executed by said processor, comprising:
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first data dividing means for dividing input image data into m- by n-pixel blocks each with a predetermined number of bits, m and n each being an integer; first data encoding means for encoding, according to frequency information included in said input image data, each of said m- by n-pixel blocks into a first data block including a plurality of frequency data elements; second data encoding means for encoding said each of said m- by n-pixel blocks into a second data block that represents said image data in fewer bits than said predetermined number of bits for each m- by n-pixel block, elements of said second data block including an image density characterizing a pixel image density value common to at least two pixels in an m- by n-pixel block being encoded by said second data encoding means, locations of pixels having said image density, and a flag for specifying an image type; first image type determining means for determining as to whether a number of different image density values, which pertain to pixels included in each of said m- by n-pixel blocks, is equal to a first predetermined value; first data selecting means for selecting said first data block from said first data encoding means when said first image type determining means determines that the number of said different image density values of said m- by n-pixel block is different from said first predetermined value and said second data block from said second data encoding means when said first image type determining means determines that the number of said different image density values of said m- by n-pixel block is equal to said first predetermined value; first data decoding means for decoding said first data block into an m- by n-pixel block which is substantially similar to said m- by n-pixel block previously divided by said first data dividing means; second data decoding means for decoding said second data block into an m- by n-pixel block which is substantially similar to said m- by n-pixel block previously divided by said first data dividing means; second image type determining means for determining whether said flag data element is equal to a second predetermined value; and second data selecting means for selecting said m- by n-pixel block from said first data decoding means when said second image type determining means determines that said flag data element is different from said second predetermined value and said m- by n-pixel block from said second data decoding means when said second image type determining means determines that said flag data element is equal to said second predetermined value.
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59. A computer product having computer readable instructions encoded therein for implementing an image data encoding/decoding apparatus which has a processor for executing said computer readable instructions, said computer program product, when said computer readable instructions are executed by said processor, comprising:
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first data dividing means for dividing input image data into m- by n-pixel blocks each with a predetermined number of bits, m and n each being an integer; first data encoding means for encoding, according to frequency information included in said input image data, each of said m- by n-pixel blocks into a first data block including a plurality of sub-band data elements; second data encoding means for encoding said each of said m- by n-pixel blocks into a second data block that represents said image data in fewer bits than said predetermined number of bits for each m- by n-pixel block, elements of said second data block including an image density characterizing a pixel image density value common to at least two pixels in a m- by n-pixel block being encoded by said second data encoding means, and locations of pixels having said image density; first image type determining means for determining whether a number of different image density values, which pertain to pixels included in each of said m- by n-pixel blocks, is equal to a first predetermined value; flag generating means for generating a flag data element for specifying one of image types which are an m- by n-pixel block determined to have the number of said different image density values of said m- by n-pixel block being different from said first predetermined value by said first image type determining means, and an m- by n-pixel block determined to have the number of said different image density values of said m- by n-pixel block being equal to said first predetermined value, said flag data element being used to select one of blocks based on said first data block encoded by said first data encoding means and said second data block encoded by said second data encoding means; and compressing means for compressing said first data block encoded by said first data encoding means, said second data block encoded by said second data encoding means, and said flag data element generated by said flag generating means.
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60. A computer product having computer readable instructions encoded therein for implementing an image data encoding/decoding apparatus which has a processor for executing said computer readable instructions, said computer program product, when said computer readable instructions are executed by said processor, comprising:
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first data dividing means for dividing input image data into m- by n-pixel blocks each with a predetermined number of bits, m and n each being an integer; first data encoding means for encoding, according to frequency information included in said input image data, each of said m- by n-pixel blocks into a first data block including a plurality of sub-band data elements; second data encoding means for encoding said each of said m- by n-pixel blocks into a second data block that represents said image data in fewer bits than said predetermined number of bits for each m- by n-pixel block, elements of said second data block including an image density characterizing a pixel image density value common to at least two pixels in a m- by n-pixel block being encoded by said second data encoding means, and locations of pixels having said image density; first image type determining means for determining whether a number of different image density values, which pertain to pixels included in each of said m- by n-pixel blocks, is equal to a first predetermined value; flag generating means for generating a flag data element for specifying one of image types which are an m- by n-pixel block determined to have the number of said different image density values of said m- by n-pixel block being different from said first predetermined value by said first image type determining means, and an m- by n-pixel block determined to have the number of said different image density values of said m- by n-pixel block being equal to said first predetermined value, said flag data element being used to select one of blocks based on said first data block encoded by said first data encoding means and said second data block encoded by said second data encoding means; first data decoding means for decoding said first data block into an m- by n-pixel block which is substantially similar to said m- by n-pixel block previously divided by said first data dividing means; second data decoding means for decoding said second data block into an m- by n-pixel block which is substantially similar to said m- by n-pixel block previously divided by said first data dividing means; second image type determining means for determining whether said flag data element is equal to a second predetermined value; and data selecting means for selecting one of said m- by n-pixel block from said first data decoding means and said m- by n-pixel block from said second data decoding means in accordance with said flag data element.
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61. A computer product having computer readable instructions encoded therein for implementing an image data encoding/decoding apparatus which has a processor for executing said computer readable instructions, said computer program product, when said computer readable instructions are executed by said processor, comprising:
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a first data divider configured to input image data into m- by n-pixel blocks each with a predetermined number of bits, m and n each being an integer; a first data encoder configured to encode, according to frequency information included in said input image data, each of said m- by n-pixel blocks into a first data block including a plurality of frequency data elements; a second data encoder configured to encode said each of said m- by n-pixel blocks into a second data block that represents said image data in fewer bits than said predetermined number of bits for each m- by n-pixel block, elements of said second data block including an image density characterizing a pixel image density value common to at least two pixels in a m- by n-pixel block being encoded by said second data encoder, locations of pixels having said image density, and a flag data element for specifying an image type; a first image type determiner configured to determine whether a number of different image density values, which pertain to pixels included in each of said m- by n-pixel blocks, is equal to a first predetermined value; and a first data selector configured to select said first data block from said first data encoder when said first image type determiner determines that the number of said different image density values of said m- by n-pixel block is different from said first predetermined value and said second data block from said second data encoder when said first image type determiner determines that the number of said different image density values of said m- by n-pixel block is equal to said first predetermined value.
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62. A computer product having computer readable instructions encoded therein for implementing an image data encoding/decoding apparatus which has a processor for executing said computer readable instructions, said computer program product, when said computer readable instructions are executed by said processor, comprising:
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a first data divider configured to divide input image data into m- by n-pixel blocks each with a predetermined number of bits, m and n each being an integer; a first data encoder configured to encode, according to frequency information included in said input image data, each of said m- by n-pixel blocks into a first data block including a plurality of frequency data elements; a second data encoder configured to encode said each of said m- by n-pixel blocks into a second data block that represents said image data in fewer bits than said predetermined number of bits for each m- by n-pixel block, elements of said second data block including an image density characterizing a pixel image density value common to at least two pixels in a m- by n-pixel block being encoded by said second data encoder, locations of pixels having said image density, and a flag data element for specifying an image type; a first image type determiner configured to determine whether a number of different image density values, which pertain to pixels included in each of said m- by n-pixel blocks, is equal to a first predetermined value; a first data selector configured to select said first data block from said first data encoder when said first image type determiner determines that the number of said different image density values of said m- by n-pixel block is different from said first predetermined value and said second data block from said second data encoder when said first image type determiner determines that the number of said different image density values of said m- by n-pixel block is equal to said first predetermined value; a first data decoder configured to decode said first data block into an m- by n-pixel block which is substantially similar to said m- by n-pixel block previously divided by said first data divider; a second data decoder configured to decode said second data block into an m- by n-pixel block which is substantially similar to said m- by n-pixel block previously divided by said first data divider; a second image type determiner configured to determine whether said flag data element is equal to a second predetermined value; and a second data selector configured to select said m- by n-pixel block from said first data decoder when said second image type determiner determines that said flag data element is different from said second predetermined value and said m- by n-pixel block from said second data decoder when said second image type determiner determines that said flag data element is equal to said second predetermined value.
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63. A computer product having computer readable instructions encoded therein for implementing an image data encoding/decoding apparatus which has a processor for executing said computer readable instructions, said computer program product, when said computer readable instructions are executed by said processor, comprising:
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a first data divider configured to divide input image data into m- by n-pixel blocks each with a predetermined number of bits, m and n being an integer; a first data encoder configured to encode, according to frequency information included in said input image data, each of said m- by n-pixel blocks into a first data block including a plurality of sub-band data elements; a second data encoder configured to encode said each of said m- by n-pixel blocks into a second data block that represents said image data in fewer bits than said m- by n-pixel block, elements of said data block including an image density characterizing a pixel image density value common to at least two pixels in a m- by n-pixel block being encoded by said second data encoder and locations of pixels having said image density; a first image type determiner configured to determine whether a number of different image density values, which pertain to pixels included in each of said m- by n-pixel blocks, is equal to a first predetermined value; a flag generator configured to generate a flag data element for specifying one of image types which are an m- by n-pixel block determined to have the number of said different image density values of said m- by n-pixel block being different from said first predetermined value by said first image type determiner, and an m- by n-pixel block determined to have the number of said different image density values of said m- by n-pixel block being equal to said first predetermined value, said flag data element being used to select one of blocks based on said first data block encoded by said first data encoder and said second data block encoded by said second data encoder; and a compressor configured to compress said first data block encoded by said first data encoder, said second data block encoded by said second data encoder, and said flag data element generated by said flag generator.
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64. A computer product having computer readable instructions encoded therein for implementing an image data encoding/decoding apparatus which has a processor for executing said computer readable instructions, said computer program product, when said computer readable instructions are executed by said processor, comprising:
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a first data divider configured to divide input image data into m- by n-pixel blocks each with a predetermined number of bits, m and n each being an integer; a first data encoder configured to encode, according to frequency information included in said input image data, each of said m- by n-pixel blocks into a first data block including a plurality of sub-band data elements; a second data encoder configured to encode said each of said m- by n-pixel blocks into a second data block that represents said image data in fewer bits than said predetermined number of bits for each m- by n-pixel block, elements of said data block including an image density characterizing a pixel image density value common to at least two pixels in a m- by n-pixel block being encoded by said second data encoder and locations of pixels having said image density; a first image type determiner configured to determine whether a number of different image density values, which pertain to pixels included in each of said m- by n-pixel blocks, is equal to a first predetermined value; a flag generator configured to generate a flag data element for specifying one of image types which are an m- by n-pixel block determined as that the number of said different image density values of said m- by n-pixel block being different from said first predetermined value by said first image type determiner, and an m- by n-pixel block determined to have the number of said different image density values of said m- by n-pixel block being equal to said first predetermined value, said flag data element being used to select one of blocks based on said first data block encoded by said first data encoder and said second data block encoded by said second data encoder; a first data decoder configured to decode said first data block into an m- by n-pixel block which is substantially similar to said m- by n-pixel block previously divided by said first data divider; a second data decoder configured to decode said second data block into an m- by n-pixel block which is substantially similar to said m- by n-pixel block previously divided by said first data divider; a second image type determiner configured to determine whether said flag data element is equal to a second predetermined value; and a data selector configured to select one of said m- by n-pixel block from said first data decoder and said m- by n-pixel block from said second data decoder in accordance with said flag data element.
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Specification