The differential values of adjacent pixels of a group of pixels are calculated and are re-ordered by referring to the magnitude of pixels of a neighboring line. Another time of calculation of differential values of the re-ordered differential values of adjacent pixels is done and the results go through a procedure of a variable length coding. When complex pattern happened, a market code is asserted to break the calculating the differences of adjacent pixels followed by a new raw pixel data as a reference for a new group of pixel. The variable length coding only keeps the “Quotient” and “Remainder” with the “Divider” implicitly done by prediction.