O
`
`Ulllt?d States Patent [19]
`Bobick
`
`[11] Patent Number:
`[45] Date of Patent:
`
`4,568,983
`Feb. 4, 1986
`
`[54] IMAGE DATA
`COMPRESSION/DECOMPRESSION ~
`[75] Inventor: Thomas W. Bobick, Richardson, Tex.
`[73] Assignee: The Mead Corporation, Dayton,
`Ohio
`
`[56]
`
`,
`
`,
`
`e er 6 a . ...... ..
`
`..
`
`358/260
`
`.
`
`.
`
`.
`
`_
`
`4,048,656 9/1977 Ishn et a1. . . . . . . . . . . .
`
`. . . .. 358/261
`
`_
`
`_
`
`References Cited
`U_S_ PATENT DOCUMENTS
`_
`_
`wugnngthzilm """"""""""""""" "
`5,32,25,32 1(9);
`3,992,572 11/1976 Nakagome et aL _
`--
`4,070,694 1/1978 Sakamoto a 8L
`4,121,259 10/1978 Preuss et a1.
`4,135,214 1/1979
`4,327,379 4/1982
`4,376,933 3/ 1983
`
`Assistant Examiner—John K. Peng
`Attorney, Agent, or Firm-Biebel, French & Nauman
`[57]
`ABSTRACT
`Scanned image data is assembled to represent scanned
`strips of a document each strip comprising a plurality of
`scanned lines. The lines of each strip are read in parallel
`‘
`to form data words de?ning columns of the scanned
`[21] Appl' No" 559’142
`strips. The data words are encoded by means of Huff
`[22] Filed:
`Dec. 7, 1983
`ma“ and run‘lel‘llgth °°dmg t° generate ?xed'lengltlh
`[51] Int. (31.4; .......................................... .. H04N 1/415
`°°ded “"15 “’ ‘ch. are °°ncatenated F0 ‘ePFesem‘ e
`[52] U s on ............................ .. 358/260- 358/261-
`document. Each strip of coded words 1s reviewed and
`'
`'
`' '
`' ' ' '
`'
`’ 358/263’
`“nwded data ‘S subsmuted f°r °°ded data m the even‘
`[58] Field of Search ..................... .. 358/260, 261, 263;
`340/347 DD the coded data exceeds the uncoded data. Text data and
`continuous tone data are encoded using different encod
`ing techniques due to their varying characteristics. Syn
`chronization words are used to pre?x all coded data
`stnps; to pre?x and suf?x all uncoded data strips; to
`de?ne all white and all black strips; and, to indicate
`changes 1n data type, 1.e., text to continuous tone or v1ce
`versa. At least the ?rst and the last data word of each
`encoded strlp. are de?ned as text so that decoding can
`commence 115mg text decodmg techmques- The 11t1_11.Za
`tion of ?xed-length coded words, the forced de?mtlon
`of at least the ?rst and last data word of each strip as
`text, and the synchronization code words permit bidi
`rectional decoding of encoded data blocks.
`
`358/260
`358/261
`358/261
`358/261
`353/261
`
`,
`
`,
`
`B _ k
`
`no man e
`
`tal
`
`. ................ ..
`
`Primary Examiner-James J. Groody
`
`16 Claims, 46 Drawing Figures
`
`100
`
`M
`
`/'°8
`COMPREsSlON
`CONTROLLER
`
`[104
`TEXT
`COMPRESSOR *
`
`[112
`UNCOMZQESSED
`CORITROL
`
`[110
`s
`OUTPUT gCATZREUSTED
`BUFFER
`*
`
`INPUT
`BUFFER 1
`L102
`
`k
`I/
`
`CONTINUOUS
`comgg'ggson
`
`0001
`
`Realtime 2002
`SAP America v. Realtime
`IPR2016-00783
`
`

`
`U. S. Patent Feb. 4, 1986
`
`Sheet 1 of 41
`
`4,568,983
`
`GROUP 0
`
`HEX VALUE
`
`GROUP I
`
`HEX VALUE
`
`GROUPQZ
`
`HEX VALUE
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`0002
`
`

`
`US Patent \ Feb. 4, 1986
`
`Sheet 2 0f41
`
`4,568,983
`
`TEXT CODES
`
`Output Group 000
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`

`
`U.S. Patent Feb. 4, 1986
`
`Sheet 3 0f41
`
`4,568,983
`
`TEXT CODES (CCNTJ
`
`Output Group 010
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`

`
`US. Patent Feb.4, 1986
`
`Sheet4of4l
`
`4,568,983
`
`TEXT CODES (CON’L)
`
`Output Group 011
`
`lll
`
`CCCC
`
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`
`

`
`U.S. Patent Feb. 4, 1986
`
`Sheet 5 of 41
`
`4,568,983
`
`F I6. 20
`w
`
`Output Group 011
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`
`

`
`US. Patent Feb. 4, 1986
`
`Sheet6of4l
`
`4,568,983
`
`TEXT CODES (CONT. )
`
`Output Group 100
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`

`
`U.S.‘ Patent Feb. 4, 1986
`
`Sheet7of4l
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`4,568,983
`
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`

`
`US, Patent Feb. 4, 1986
`
`Sheet80f4l
`
`4,568,983
`
`SYNC CODES
`
`F'IG.9
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`

`
`~ US. Patent Feb. 4,1986
`
`Sheet9 of41
`
`4,568,983
`
`FIG.8
`
`CQITDIUOUS TCNE QDDES
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`
`100 BBBB DODlD2D3D4
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`(BEBE)
`
`FOLLOWING CODES MAY BE SAME
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`
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`
`2 Vertical Data Patterns
`voandvl
`
`l 1
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`0010
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`

`
`U.S. Patent
`
`Feb. 4, 1986
`
`Sheet 10 of41 4,568,983
`
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`U.S. Patent
`
`Feb. 4, 1986
`
`Sheet 11 of4l 4,568,983
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`U.S. Patent Feb. 4,1986
`
`Sheet 12 of4l 4,568,983
`
`14
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`

`
`U.S. Patent
`
`Feb. 4, 1986
`
`Sheet 13 of4l 4,568,983
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`
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`US. Patent Feb. 4, 1986
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`Sheet14 01‘41 4,568,983
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`
`U.S. Patent Feb. 4, 1986
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`‘SheetlS 0f41 4,568,983
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`US. Patent Feb. 4, 1986
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`Sheetl6 of4l 4,568,983
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`US. Patent F6114, 1986
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`U.S. Patent Feb. 4, 1986
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`Sheetl8 of41 4,568,983
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`US. Patent Feb. 4, 1986
`
`Sheet 19 of4l 4,568,983
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`U.S. Patent
`
`Feb. 4, 1986
`
`Sheet20 of41 4,568,983
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`U.S. Patent
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`Feb. 4, 1986
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`Sheet 21 of41 4,568,983
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`U.S. Patent
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`Feb. 4, 1986
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`U.S. Patent
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`Feb. 4, 1986
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`Sheet 24 of4l 4,568,983
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`U.S. Patent
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`Feb. 4, 1986
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`Sheet25 of41 4,568,983
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`U.S. Patent
`
`Feb. 4, 1986
`
`Sheet26 of41 4,568,983 »
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`
`U.S. Patent
`
`Feb. 4,1986
`
`Sheet 27 of41 4,568,983
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`
`U.S. Patent
`
`Feb. 4,1986
`
`Sheet28 of41 4,568,983
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`

`
`U.S. Patent Feb. 4, 1986
`
`Sheet29 of4l 4,568,983
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`
`U.S. Patent
`
`Feb. 4, 1986
`
`Sheet 30 of41 4,568,983
`
`_.u_mm.Eio.dm._m
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`
`

`
`U.S. Patent Feb. 4, 1986
`
`Sheet 31 of 41 4,568,983
`
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`0032
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`0032
`
`

`
`U.S. Patent
`
`Feb. 4, 1986
`
`2
`
`14
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`0033
`
`
`

`
`U. S. Patent
`
`Feb. 4, 1986
`
`Sheet 33 of4l 4,568,983
`
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`0034
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`

`
`—U.S. Patent
`
`Feb. 4,1986
`
`Sheet 34 of41 4,568,983
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`
`U.S. Patent
`
`Feb. 4, 1986
`
`Sheet 35 of41 4,568,983
`
`_2.6
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`

`
`U.S. Patent
`
`Feb. 4,1986
`
`Sheet 36 of4l 4,568,983
`
`O.
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`
`

`
`U.S. Patent
`
`Feb. 4, 1986
`
`Sheet 38 em 4,568,983
`
`mm.o_1._
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`0039
`
`
`
`

`
`U.S. Patent
`
`Feb. 4,1986
`
`Sheet 39 of41 4,568,983
`
`mm.o_.._
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`0040
`
`

`
`U.S. Patent
`
`Feb. 4, 1986
`
`Sheet 40 of 41 4,568,983
`
`
`
`004
`
`043
`
`SOF
`
`OD4
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`F20
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`08C
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`940
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`
`
`STRIP l
`
`STRIP 2
`
`0041
`
`0041
`
`

`
`U.S. Patent
`
`Feb. 4, 1986
`
`Sheet4l of4l 4,568,983
`
`COMPRESSED DATA CODE IN BINARY AND HEX FORMAT
`(Contd.)
`
`STRIP 3
`
`004
`
`ZF8
`
`A10
`
`A97
`
`B45
`
`22A
`
`214
`
`061
`
`96B__
`AA5
`
`90F
`
`020
`
`969
`
`EE7
`
`O03
`
`AAO
`
`CBB
`
`B3E
`
`0042
`
`0042
`
`

`
`1
`
`.
`IMAGE DATA
`COMPRESSION/DECOMPRESSION
`
`4,568,983
`
`2
`pressed in either direction and then utilized to duplicate
`the document.
`
`SUMMARY OF THE INVENTION
`
`In accordance with the present invention, data gener-
`ated, for example, by scanning a document to be dupli-
`cated, is assembled to represent scanned strips of the
`document with each strip comprising a plurality of
`scanned lines. The assembled scanned line data are read
`in parallel to form data words corresponding to col-
`umns of the scanned strips. The data words are re-
`viewed and consecutive data words which are identical
`to one another are counted to determine run lengths of
`consecutive,
`identical data words. Each run of data
`words read and the corresponding run length are en-
`coded into a fixed-length coded word with all fixed-
`length coded words being concatenated to represent the
`document.
`
`The individual data words are encoded by employing
`Huffman coding such that the data words which are
`statistically more likely to occur in a class of documents
`to be duplicated are encoded using a lesser number of
`data bits than data words which are less likely to occur.
`The Huffman encoded data words and the run lengths
`for the data words are combined to form the fixed-
`length coded words.
`_
`A synchronization word prefixes each encoded
`scanned strip to enable the fixed-length coded words to
`be decoded or decompressed from either direction.
`When decompressed in the forward direction, the syn-
`chronization words indicate characteristics of the
`scanned lines of coded data to be decoded, while in the
`reverse direction,
`the synchronization words verify
`characteristics of the information just decoded.
`For quality duplication of documents, appropriate
`portions of each document are classified as either text or
`continuous tone. While text and continuous tone data
`may be encoded using the same technique, continuous
`tone data does not have the same grouping characteris-
`tics or appreciable run lengths for such groups. Accord-
`ingly, it is advantageous to encode continuous tone data
`by means of a different technique than that used for text
`data. In accordance with the present invention, data
`representative of both text and continuous tone portions
`of a document can be intermixed in the compressed
`code representation even though encoded differently.
`For continuous tone data, data words comprising at
`least two columns of a scanned strip are encoded again
`using a combination of Huffman coding to encode the
`multiple column data words and run-length encoding to
`specify the runs of such data words. Preferably, contin-
`uous tone data words comprise four columns of a
`scanned strip and are referred to as print fonts. Conti-
`nous tone data words can also comprise two columns of
`a scanned strip referred to as match fonts. Finally, if
`neither print fonts nor match fonts can be identified,
`raw data is encoded.
`When a document includes both text and continuous
`tone portions, additional synchronization words are
`inserted into the encoded data to indicate transitions
`from text to continuous tone and from continuous tone
`to text herein collectively referred to as continuous
`tone/text changes. Also, at least the first and last data
`words of each scan strip are defined as text data and the
`prefixing synchronization words include an indication
`that the strip begins with text data. Bidirectional decod-
`ing is thus possible since decoding from either direction
`
`BACKGROUND OF THE INVENTION
`
`The present invention relates generally to image data
`representative of a document to be duplicated and,
`more particularly, to a method and apparatus for com-
`pressing and decompressing image data to reduce the
`storage capacity or bandwidth required for storage or
`transmission of the data, respectively.
`' Data compaction is well known in electrical systems
`to reduce storage space for data storage or channel
`bandwidth for data transmission. Data compaction
`techniques have been applied to image data produced
`by duplication or facimile systems. In such systems, a
`document is scanned to generate raw image data with
`individual data bits corresponding to small elements of
`the document. The small elements are referred to as
`picture elements or pels and the image data defines
`whether each pel is a white, no-print element or a black,
`print element. The need for compaction of such raw
`data is appreciated by observing that one square inch of
`a document may comprise a 400x400 matrix of pels for
`a high quality ink jet duplicating system, i.e., 160,000
`pels per square inch.
`One known data compaction technique is run-length
`encoding wherein the number of repetitive occurrences
`of data bits of a given data state is transmitted rather
`than the bits themselves. According to run-length en-
`coding, a 5 bit word representing the number 32 is trans-
`mitted instead of 32 consecutive and identical data bits.
`Such run-length encoding has been improved in accor-
`dance with a technique referred to as Huffman coding.
`In Huffman coding, the most commonly encountered
`run lengths in a document type to be duplicated are
`allocated to the shortest code words such that fewer
`bits are required to represent a document.
`Run-length and Huffman coding result in varying
`length code words which generally represent individual
`scan lines of a document to be duplicated. A dual line
`compaction technique is disclosed in U.S. Pat. No.
`3,916,095, issued to Weber et al. on Oct. 28, 1975. In the
`disclosed dual line compaction technique, data pairs,
`i.e., adjacent upper and lower elements of two scan
`lines, are encoded. Data pairs having the same data state
`(both white or both black) are run-length encoded and
`transitional data pairs (upper black/lower white or
`upper white/lower black) are individually encoded.
`The coding technique of the cited patent is an adaptive
`word-length code which results in varying length code
`words.
`
`While these prior art encoding arrangements provide
`data compaction for storage or transmission of image
`data, the resultant varying length code words must be
`decoded from the first encoded word to the last en-
`coded word. Often, it is desirable to decode an encoded
`data block either from the first-to-the-last encoded data
`word of from the last-to-the-first encoded data word.
`The ability to decode in either direction adds versatility
`and permits a larger variety of applications. For exam-
`ple, a document may be scanned and encoded in one
`direction and decoded and printed in the opposite direc-
`tion to facilitate duplication of the document.
`Thus, the need exists for an improved compression/-
`decompression method and apparatus for use, for exam-
`ple, in a duplicating system wherein image data repre-
`sentative of a document is compressed, stored, decom-
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`3
`initially commences on text data and continuous tone/-
`text changes are indicated by an appropriate synchroni-
`zation word.
`V
`In the interest of minimizing the size of the image data
`representing a document to be duplicated, the coded
`words generated to represent each scanned strip are
`reviewed and uncoded scanned strip data is substituted
`for generated coded words in the event that the gener-
`ated coded words exceed the uncoded scanned strip
`data. Such excesses can occur due to numerous continu-
`ous tone/text changes in a given scanned strip.
`When one or more uncompressed data strips are in-
`serted into an otherwise compressed data representation
`of a document to be duplicated, synchronization words
`are used to both prefix and suffix all such uncompressed
`data strips. The uncompressed synchronization words
`identify any such strips as being uncompressed image
`data with the suffixing synchronization words provid-
`ing for bidirectional decoding of any uncompressed
`data strips.
`It is, therefore, an object of the present invention to
`provide an improved method and apparatus for com-
`pressing and decompressing image data representative
`of a document to be duplicated.
`It is another object of the present invention to pro-
`vide an improved method and apparatus for compress-
`ing and decompressing image data representative of a
`document to be duplicated wherein scanned document
`strips comprising a plurality of individual scanned lines
`are encoded by means of a combination of Huffman and
`run-length encoding into fixed-length coded words
`with synchronization words being provided such that a
`compressed data block can be decompressed from ei-
`ther direction, i.e., from the first encoded data word to
`the last encoded data word or from the last encoded
`data word to the first encoded data word.
`It is an additional object of the present invention to
`A provide an improved method and apparatus for encod-
`v
`ing and decoding image data representative of a docu-
`ment to be duplicated wherein encoded data words
`representative of scanned document strips are reviewed
`and uncoded scanned strip data are substituted for the
`encoded data words in the event that the encoded data
`
`words exceed the uncoded. scanned strip data.
`It is yet another object of the present invention to
`provide an improved method and apparatus for encod-
`ing and decoding scanned image data strips representa-
`tive of a document to be duplicated wherein text data
`and continuous tone data are encoded utilizing different
`encoding techniques with encoded text and continuous
`tone data being included in the same data block with
`synchronization words interposed therebetween to indi-
`cate switches between the two data types, at least the
`initial and the final data words of each scanned strip
`being defined as text data to permit the initial decoding
`of each encoded data strip to commence as text data
`decoding whether decoding is initiated from the begin-
`ning of the strip or the end of the strip.
`Other objects and advantages of the present invention
`will be apparent from the following description, the
`accompanying drawings and the appended claims.
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG. 1 shows vertical data pattern groupings for text
`data strips.
`FIGS. 2A—2E show text codes used for encoding the
`text vertical pattern groupings of FIG. 1.
`
`4
`FIG. 3 is a table showing the number of text code bits
`required for encoding the text vertical data pattern
`groupings of FIG. 1 (see drawing sheet 1).
`FIG. 4 shows the code fields and run length fields for
`the text codes of FIG. 2 (see drawing sheet 1).
`FIG. 5 shows print fonts and the corresponding hex-
`idecimal
`identification numbers for
`the print
`fonts
`which are used to encode continuous tone data.
`FIG. 5A is a matrix used to preprocess continuous
`tone data prior to compression in accordance with the
`present invention (see drawing sheet 9).
`FIGS. 6 and 7 show left match fonts and right match
`fonts, respectively, which are used to encode continu-
`ous tone data.
`FIG. 8 shows continuous tone codes for encoding
`continuous tone data in accordance with the present
`invention.
`FIG. 9 shows synchronization code words in accor-
`dance with the present invention.
`FIG. 10 is a block diagram of a data compression
`system in accordance with the present invention.
`FIG. 11 is a schematic diagram of the input section of
`the test compressor of FIG. 10.
`FIG. 12 is a schematic diagram of a text compressor
`state controller for the text compressor of FIG. 10.
`FIG. 13 is a schematic diagram of additional text
`compressor control circuitry of the present invention.
`FIG. 14 is a schematic diagram of counting and asso-
`ciated circuitry utilized for compressing text data.
`FIGS. 15 and 16 are schematic diagrams of the text
`compressor word 0 code generator and the text com-
`pressor word 1 code generator, respectively.
`FIG. 17 is a schematic diagram of font determination
`circuitry for encoding continuous tone data.
`FIG. 18 is a schematic diagram of a continuous tone
`output selector circuit.
`FIGS. 19 and 20 form a schematic diagram of a con-
`tinuous tone compressor state controller.
`FIG. 21 is a schematic diagram of the continuous tone
`input registers and the circuitry for evaluating whether
`five successive print fonts are equal to one another or
`equal plus one.
`FIG. 22 is a schematic diagram of comparator cir-
`cuits for determining whether a series of five recog-
`nized print fonts are equal to one another.
`FIG. 23 is a series of programmable read-only memo-
`ries which determine the lowest value print font of a
`series of five print fonts.
`FIGS. 24 and 25 form a schematic diagram of the
`uncompressed data control 112 of FIG. 10.
`FIG. 26 is a block diagram of a data decompression
`system in accordance with the present invention.
`FIG. 27 shows input and decode latches of FIG. 26.
`FIG. 28 shows synchronization code word and mode
`detect circuitry of FIG. 26.
`FIG. 29 is a schematic diagram of a portion of the text
`mode decoder control of FIG. 26.
`FIG. 30 shows the circuitry for generating the output
`buffer control signals and the run-length select signals
`for data decompression.
`FIG. 31 shows the compressed text data decoder
`circuitry of FIG. 26.
`FIG. 32 shows run-length counters which determine
`the number of times a text pattern is loaded into the
`output buffer.
`FIGS. 33 through 36 are a schematic diagram of a
`continuous tone data decompressor in accordance with
`the present invention.
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`FIG. 37 shows the circuitry for unpacking uncom-
`pressed data.
`FIGS. 38 through 40B illustrate an example of image
`data encoded in accordance with the present invention.
`DETAILED DESCRIPTION OF THE
`INVENTION
`
`In accordance with the present invention, image data
`obtained by scanning a document to be duplicated is
`encoded on a scanned strip basis. The scanned strips of
`the image data each comprises a plurality of contiguous
`scanned lines, preferably four scanned lines, across the
`document to be duplicated. A review of a variety of
`documents to be duplicated