A study of Mixed-Mode Communication based on Word-Unit Processing and Graphic Commands

提出了基于模式识别技术的英语文本编码算法。首先，通过加权传播和收缩操作，将文档的每一页分割成包含文本、表格、图形等特定类型内容的块。对于文本块，使用包含26个前缀、338个词根和24个后缀的字典进行单词识别，然后将识别出的单词编码为数字信号。未识别字被编码到ISO码中，用于信息交换字符。对于表块，采用霍夫变换提取直线，并用图形命令传递直线属性。表块中的余数被编码成数字信号，就像文本块一样。对于图形块，再次通过Hough变换提取直线，通过模式匹配识别*、*、*、*、*、*六种类型的符号。线条和符号元素的属性也通过图形命令传递。在去除线条和符号后，剩余的图像采用跳行扫描的MMR编码方案进行编码。使用前面和后面的行恢复跳过的行。跳过的行数从0,1或3中选择，参考恢复图像上的错误像素数。为了传输文件，在编码信号中加入文件轮廓、布局对象、表示函数等编辑信息。对包括文本和黑白图像在内的英文文档的传输进行计算机仿真，结果表明，处理后的信号与传统传真信号的总体压缩比为124.9。对于文本块，采用字单位编码，压缩比比采用字符编码提高1.91倍。

The encoding algorithm of English texts using pattern recognition technique is proposed.First, each page of document is segmented into blocks which contain specific kind of contents such as text, tables, graphs etc. by the weighted propagation and shrinking operation.For the text blocks, words identification is carried out using dictionaries of 26 prefixes, 338 roots and 24 suffixes and then the identified words are encoded into digital signals. Unidentified words are encoded into the ISO code for information interchange character.For the table blocks, straight lines are extracted by the Hough trans form and the attributes of lines are transmitted with the graphic commands. The remainders in the table blocks are encoded into digital signals just like as the text blocks.For the graphic blocks, straight lines are again extracted by the Hough transform and symbols of six types: *, *, *, *, *, * are identified by pattern matching. The attributes of lines and symbol elements are also transmitted by the graphic commands. After the lines and symbols are removed, the remaining picture is encoded by the MMR coding scheme with line-skipped scanning. The skipped lines are restored using the preceding and following lines.The number of skipped lines are selected out of 0,1 or 3 referring the number of error pixels on the restored picture.To transmit the documents, editing information indicating document profile, layout object, presentation function etc. is added to the encoded signals.The computer simulation results for transmission of English documents including texts and black-and-white images show that the overall compression ratio of the processed signal to the conventional facsimile signal is 124.9.With regard to the text blocks, by adopting the word-unit encoding, 1.91 times of compression ratio improvement is achieved compared with the encoding by characters.