Real time data compression/decompression scheme for facsimile transmission system
AssigneeAM International, Inc.
InventorsLarry M. Wolfrum, Frederick C. Barrett
Life of this patent
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Abstract
A graphic image represented by a two-level pel-to-pel definition is compressed by one-dimensional redundancy reduction coding using an entropy preserving algorithm which allows for real time reduction of the pel-to-pel data without any loss in image resolution. The compressed data is concatenated for transmission and then separated and decoded back to a pel-to-pel format for defining a facsimile image.
Claims18
A method of one-dimensional redundancy reduction coding, transmission and decoding of binary image data by use of an entropy preserving algorithm, the image data of the type including two-level pel representation of an image to be transmitted, comprising the steps of:
- (a) generating an image definition comprising a serial stream of binary data bits, each bit representing a single pel of either a first level or a second level;
- (b) assigning a predetermined binary code N having a number of data bits n representing a runlength of consecutive pels of a single level;
- (c) assigning a prefix P for defining with N a codeword representation of a runlength, the prefix P having a number of data bits p, whereby the total number of data bits representing each runlength of pels is defined by a codeword comprising a prefix P and a code N having (p+n) data bits;
- (d) concatenating consecutive codewords;
- (e) framing the concatenated codewords into output words W each having a fixed, predetermined number of data bits w;
- (f) transmitting the output words;
- and
- (g) receiving and decoding the transmitted output words for generating therefrom a serial stream of data bits, each bit representing a single pel of one of said levels, by searching in said output words for the prefix P associated with a codeword and identifying therefrom the (p+n) bits associated therewith.
An apparatus for one-dimensional redundancy reduction coding, transmitting and decoding binary data by use of an entropy preserving algorithm, the data representing an image in a plurality of two-level pels, comprising:
- (a) means for generating an image definition comprising a serial stream of binary data bits, each bit representing a single pel of either a first level or a second level;
- (b) means for defining the boundaries between runs of consecutive pels of the same level by using an entropy preserving algorithm, wherein there is further:
- (i) means for assigning a predetermined binary code N having a number of data bits n representing a runlength of consecutive pels of a single level;
- (ii) means for assigning a prefix P for defining with N a codeword representation of a runlength, the prefix P having a number of data bits p, whereby the total number of data bits representing each runlength of pels is defined by a codeword comprising a prefix P and a code N having (p+n) data bits;
- (c) means dependent on said boundaries for generating a binary codeword representing each of said runs;
- (d) means for concatenating the first w bits of a first group of consecutive codewords to define an output word;
- (e) means for separating and storing any residue bits r in the first group of codewords in excess of w bits;
- (f) means for defining another output word from the next subsequent group of codewords by concatenating the first (w-r) bits of said group with the residue bits r of the first group of codewords;
- (g) means for transmitting the output words;
- and
- (h) means for extracting the codewords from said output words for reformation of the image in pel-to-pel format.
Dependencies are inferred from the claim text.