JPS63292769A - Compressing method for picture data - Google Patents

Abstract

PURPOSE:To reduce the quantity of transmitting information by transmitting encoded data obtained by compressing and encoding a picture formed by reducing picture data and data indicating the exclusive OR of a picture obtained by reenlarging the reduced picture and an original. CONSTITUTION:Raw picture data stored in a memory 2 is reduced by a picture processor 3 and stored in a memory 4 for reduced data. The picture processor 3 enlarges this reduced data to an original size to take the data of the exclusive OR with the raw picture and store in a memory 5 for difference data. In an input and output device 6, the reduced data stored in the memory 4 is compressed by encoding, an enlargement ratio is added to transmit, and since the difference data stored in the memory 5 is a contour graphic, it is transmitted by a simple compressing method. Thereby, a compressibility is improved in comparison with the case the raw picture is directly compressed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a data compression method for efficiently transmitting image data with less redundancy.

[Prior art]

2. Description of the Related Art Conventionally, in image transmission devices such as facsimiles, images are compressed and encoded before being transmitted in order to improve transmission efficiency.

However, in conventional compression encoding, the image data to be transmitted is directly compressed, and no processing is applied to the data before compression, resulting in a high level of data redundancy.

〔the purpose〕

The present invention has been made in view of the above points, and relates to an image data compression method that makes it possible to reduce the amount of information to be transmitted and at the same time to reduce transmission time and transmission cost.

〔Example〕

FIG. 1 is a block diagram of an image data transmission device according to an embodiment of the present invention.

In the figure, 1 is a microcomputer (hereinafter referred to as MPU), 2 is a memory that stores image data, 3 is an image processor that has an image enlargement/reduction function, 4 is a memory that stores reduced image data, and 5 is an image 6 is an input/output device.

A data compression method in the image data transmission apparatus shown in FIG. 1 will be explained using FIG. 2.

a is a raw image before compression. Image data representing this raw image (g!, a) is stored in the memory 2. This is reduced by the image processor 3 as shown in b, and is stored in the reduced data memory 4.

Next, the image processor 3 enlarges this reduced data b to its original size and performs an exclusive OR (X0R
) and store this result as C in the differential data memory 5.

That is, b = (reduction of a) c=(enlargement of b)XORa The relationship is

Furthermore, because of the relationship a=(enlargement of b)XORc, the original image a can be reproduced by giving b and c.

Therefore, the files 4 and 5 respectively stored in the memories 4 and 5 are sent to other terminals or storage devices via the input/output device 6. Let d and e be the data sent to the terminal or storage device in this way.

At this time, if the enlargement rate of d is known on the receiving side, f=(enlargement of d)XORe, and the receiving side can obtain the same image f as the raw image a.

In addition, in the input/output device 6, the data b stored in the memory 4 is compressed by an encoding method such as the M2R method or the MR method, and transmitted with an enlargement factor added.
Since the data of C stored in is a contour figure type, it is transmitted using a simple compression method.

This further improves the compression rate compared to the case where raw images are directly compressed.

〔effect〕

By compressing data using the compression method according to the present invention described above, the transmission time during communication is shortened and the communication cost is reduced. Furthermore, since the amount of data is small when stored in a storage device, a large amount of data can be stored.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an image data transmission device, and FIG. 2 is a diagram showing compression/decompression of image data. 1 is an MPU, 2 and 4.5 are memories, and 3 is an image processor.

Claims (1)

[Claims] An image data compression method characterized by transmitting encoded data obtained by compressing and encoding an image obtained by reducing image data, and data representing an exclusive OR of an image obtained by re-enlarging the reduced image and the original image. .