A coding scheme of dither image using two types of information

This paper presents a data compression scheme which uses the statistical properties of ordered dither image by vector representation. When a part of the dither image corresponding to n x n dithering matrix is described as a vector, it is observed that there is high correlation ratio between neighbor blocks for level information (the number of black pixels in the vector), the resolution information (the number of kinds of vectors) is a few, and their frequency distribution is very biased. Thus, if these two kinds of information on vector are coded separately by the variable length coding scheme, then high compression ratio can be attained for transmission and storage of dither image.