Picture transfer method and apparatus therefor

A picture transfer method for analyzing a picture into picture cells, forming a plurality of large picture cells, reading out the densities of said picture cells, and restoring said picture therefrom, which comprises the steps of:

• dividing said picture into a plurality of small picture cells;
• quantizing the density of each of said plurality of small picture cells to obtain a binary density level for each picture cell;
• forming a plurality of large picture cells from said plurality of small picture cells, each of said large picture cells being formed from four neighboring small picture cells;
• determining the density level of each of said plurality of large picture cells by adding the binary density levels of the four small picture cells forming each large picture cell, said density level of each large picture cell being expressed as one of N gray levels;
• determining one or a plurality of n least frequently occurring gray levels among said N gray levels of said large picture cells;
• encoding said one or a plurality of n least frequently occurring levels;
• compressing said N gray levels into (N-n) gray levels by converting said n least frequently occurring gray levels among said N gray levels into other gray levels among said N gray levels;
• encoding said plurality of large picture cells utilizing said (N-n) gray levels;
• transmitting said encoded n least frequently occurring gray levels and said plurality of large picture cells;
• decoding said transmitted encoded n least frequently occurring gray levels and said plurality of large picture cells to produce a plurality of restored large picture cells having density levels expressed as (N-n) gray levels;
• dividing each of said plurality of restored large picture cells into four small restored picture cells;
• comparing the density level of each one of said plurality of restored large picture cells to the density levels of each of said plurality of restored large picture cells surrounding said each one of said plurality of restored large picture cells and assigning one of a white and black density level to each of four small restored picture cells contained in said each one of said restored large picture cells based on the result of said comparison.