System for decoding compressed data

Details System for decoding compressed data System for decoding compressed data

1981-04-17

1985-01-08

Orsino, Jr., Joseph A.

Facsimile and static presentation processing

Facsimile

Recording apparatus

H04N 712

Patent

active

044929838

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

(a) Field of the Invention
The present invention relates to a system for decoding compressed data. The system of the present invention is used for decoding compressed data of a facsimile data transmission.
(b) Background of the Prior Art
In general, data compression has been used for speeding up facsimile data transmission.
A prior art technique of coding and decoding compressed data using correlationship in data of adjacent scan lines is illustrated in FIGS. 1 and 2A through 2E. The prior art system for decoding compressed data is illustrated in FIG. 1. The system of FIG. 1 comprises a memory 1 for storing the compressed data, a circuit 2 for equalizing bit lengths of codes and a shift register 8 for a preceding scan line. The sytem also includes a circuit 46 for detecting color change elements, a circuit 47 for generating shift pulses and a circuit 48 for counting addresses on the preceding scan line a. Additionally included is a circuit 64 for addition/substraction and a circuit 65 for addition. The systems further includes a memory 76 for the address of a color change element in question, a circuit 72 for restoring the picture elements for a current scan line, a circuit 74 for counting addresses on the current scan line, a device 73 for reproducing the picture and a memory 75 for a current scan line. The circuit 2 for equalizing the bit lengths of codes produces data D3 for the selection of a reference correlated color change element, data D11 for a relative distance between the reference correlated color change element and the color change element in question or needed and data D12 for a distance between the last preceding color change element and the independent color change element in question.
The procedures which are carried out by the system of FIG. 1 will be explained with reference to color element patterns of pictures illustrated in FIGS. 2A through 2E. In FIGS. 2A through 2E patterns of the pictures along the current scan line (a) and the preceding scan line (b) are illustrated. Line scans are carried out horizontally from the left side to the right side, while line-by-line scans are carried out vertically from the top side to the bottom side. Hatched picture elements represent black elements, while non-hatched picture elements represent white elements. P.sub.1, P.sub.2, P.sub.3, P.sub.x and Q are the color change elements. Color changes from white to black at P.sub.1, P.sub.2, P.sub.3 and Q, while color changes from black to white at P.sub.x. The nature of these color change elements are as follows.
(1) Q is the color change element in question or needed color change element on the current scan line.
(2) P.sub.x is the last preceding color change element on the current scan line with respect to Q.
(3) P.sub.1 is a color change element on the preceding scan line the type of which color change is the same as that of the type of color change of the color change element in question. In FIGS. 2A through 2E, for example, the color changes from white to black both at Q and P.sub.1.
(4) P.sub.2 is the next color change element on the preceding scan line the type of which color change is the same as that of the color change of P.sub.1.
There are two kinds of color change elements in question Q in FIGS. 2A through 2E. That is, the color change elements Q in FIGS. 2A, 2B and 2C are "correlated" color change elements, while the color change elements Q in FIGS. 2D and 2E are "independent" color change elements.
The difference between a correlated color change element and an independent color change element is as follows. That is, if there is a run of picture elements, i.e. the continuous sequence of picture elements, which have the same color as the color of the color change element in question on the current scan line, existing on the preceding scan line which overlaps the run of picture elements starting with the color change element in question on the current scan line and does not overlap the immediately preceding run of picture elements, which have the same color as the

REFERENCES:
patent: 4245257 (1981-01-01), Yamazaki et al.

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