1. A method of encoding digital data representative of a document to be duplicated and obtained by scanning said document, said digital data including both text data and continuous tone data and said method comprising the steps of: assembling said digital data into scanned strips of said document with each scanned strip comprising a plurality of scan lines of said document; reading the scan lines in parallel to form data words defining columns of said scanned strips; counting the number of consecutive data words in each scanned strip which are identical to one another to determine the run lengths of said identical data words; encoding each run of data words read and the corresponding run length into a fixed length coded word, said continuous tone data being encoded such that at least some of said data words define blocks of said scanned strips each block comprising at least two individual columns of a scanned strip; concatenating all fixed length coded words to represent said document; prefixing a synchronization word to each encoded scanned strip; and inserting additional synchronization words at any transition of data words from text to continuous tone or from continuous tone to text.
1. A method of encoding digital data representative of a document to be duplicated and obtained by scanning said document, said digital data including both text data and continuous tone data and said method comprising the steps of: assembling said digital data into scanned strips of said document with each scanned strip comprising a plurality of scan lines of said document; reading the scan lines in parallel to form data words defining columns of said scanned strips; counting the number of consecutive data words in each scanned strip which are identical to one another to determine the run lengths of said identical data words; encoding each run of data words read and the corresponding run length into a fixed length coded word, said continuous tone data being encoded such that at least some of said data words define blocks of said scanned strips each block comprising at least two individual columns of a scanned strip; concatenating all fixed length coded words to represent said document; prefixing a synchronization word to each encoded scanned strip; and inserting additional synchronization words at any transition of data words from text to continuous tone or from continuous tone to text. 2. A method of encoding digital data as claimed in claim 1 wherein at least the first and last data words of each scanned strip are defined as text data and the prefixing synchronization word includes the identification of the strip as beginning with text data.