JPH02179072A - Compression method for binary picture data - Google Patents

Abstract

PURPOSE:To attain efficient and high speed compression by rearranging data for kinds of line drawing and dot drawing and coding the data by plural bits each when the binary picture data are rearranged in the unit of picture elements. CONSTITUTION:When the binary picture data are rearranged and coded in the unit of picture elements, a switching means 13 is provided before a coder 7, and if same logical values exist consecutively in the rearranged data code, the data is coded by using a code being the addition of a code based on a consecutive picture element number after the prescribed code. When the same logical value exists consecutively till the tail end of the rearranged data, the data is coded by using a code having the same bit as that of the prescribed code at its head. In the case of the other data, the data is coded by using a code added with a bit different from the head bit of the prescribed code to its head. A switching means 14 is provided after the coder 7 and the data is rearranged so that adjacent picture elements of the binary picture data are arranged.

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention: (Industrial Application Field) The present invention relates to a compression method for efficiently and quickly compressing binary image data.

(Prior Art) Since image data is enormous, it is extremely inefficient to transfer the data as it is or store it in memory. Therefore,
For example, in data transmission of halftone images and newspaper images by facsimile, compression techniques for pseudo halftone images that represent halftones using binary data are used in order to efficiently transmit the data. Conventional compression techniques include the Mll method (one-dimensional compression method; Modified tluffman Co.
ding) and MR method (two-dimensional compression method: Modify
d-READ).

(Problems to be Solved by the Invention) In the above-mentioned Mll method and MR method, binary image data is compressed along the main scanning direction, so statistical properties (resolution, etc.) differ between the main scanning direction and the sub-scanning direction. This method has the disadvantage of poor compression efficiency for binary image data. Furthermore, since the processing is done in units of 1 bit, the encoding speed is slow, making it difficult to achieve high-speed compression.

This invention was made due to the circumstances mentioned above,
An object of the present invention is to provide a compression method that can efficiently and quickly compress any binary image data such as line drawings and line drawings. Structure of the Invention; (Means for Solving the Problems) The present invention relates to a compression method for efficiently and quickly compressing binary image data. When rearranging and encoding in units, if the rearranged data has the same logical value consecutively, it is encoded with a code with a code based on the number of consecutive pixels added after the predetermined code, and the same logical value is If there are consecutively up to the end of the rearranged data, it is encoded with a code having the same bit at the beginning as the first bit of the predetermined code, and for data other than the above, bits different from the first bit of the predetermined code are encoded. This is achieved by encoding with a code added to the beginning of the data, and further, when rearranging the binary image data pixel by pixel, by aligning adjacent pixels of the binary image data.

(Function) The binary image data compression method of the present invention rearranges the binary image data so that white runs or black runs continue for a relatively long time, and encodes the data by dividing it into units of a predetermined number of bits. It can be compressed efficiently and at high speed.

(Embodiment) FIG. 1 shows an example of a block configuration of an image compression apparatus that implements the binary image data compression method of the present invention.

This image compression device includes a sorting device 3 as a main part,
An encoding device 7 and an external bag Ull such as C20 for controlling each part are provided. Then, the human-powered binary image data AD is processed by the rearranging device 3 and the encoding device 7.
The image is compressed by

At the front stage of the sorting device 3, there are provided manual buffers 1 and 2 for temporarily storing the binary image data 80, and the buffers are composed of a switch Swl and a switch SW2. By switching contact PI or contact P2 of switch SWI, 0 is written to the single-value image data in manual buffer 1 or 2, and after writing of binary image data 80 is completed, contact P3 or contact P2 of switch SW2 is changed. A switching means 12 is provided for inputting binary image data ^O to the sorting device 3 by switching the contact P4. In addition, intermediate buffers 5 and 6 for temporarily storing rearranged data NO are provided before the encoding device 7, and a switch S
The rearranged data NO processed by the rearrangement device 3 is written to the intermediate buffer 5 or 6 by switching the contact P5 or the contact P6 of the switch SW3 at a predetermined timing, and the rearranged data NO is written to the intermediate buffer 5 or 6.
A switching means 13 is provided for inputting rearranged data ND to the encoding device 7 by switching the contact P7 or P8 of the switch SW4 after the writing of data D is completed. Output buffers 8 and 9 for temporarily storing the compressed image data GO are provided downstream of the encoding device 7, and are composed of a switch SW5 and a switch SW6.
The compressed image data GO processed in is written to the output buffer 8 or 9 by switching contact P9 or contact PTO of switch SWS at a predetermined timing, and the compressed image data GO is written to all memories of one buffer. is written, the contact pH or contact P of switch SW6
Switching means 1 for reading compressed image data GO by switching 12
4 are provided.

FIG. 2 is a block diagram showing an example of the sorting device 3, in which one sub-block of binary image data AD is read out from the input buffer 1 or 2 according to the address output from the manual buffer address generator 31. is the encoding device 7
This is a block diagram showing an example, in which rearranged data ND is read out in units of 4 bits from intermediate buffer 5 or 6 according to the address output from address generator 71, and is latched by latch circuit 72. . The latched rearranged data ND is converted into 8 bits 1 to 8 bits by the encoding circuit sequencer 73, and then data is determined.

According to this determination, the address of the address generator 71 is increased or decreased. Also, the latched exchange data NO is the external bag M1. The data is encoded according to the conversion daple 74 set in advance by I, and according to the address from the address generator 71 selected by the selector 75.

Then, the encoded data is packed by the bit packing circuit 76 in bit length units generated by the coding circuit sequencer 73, and when 8 bits are complete, the compressed image data G
It is written to the output buffer 8 or 9 as D. Microprograms are written in the encoding circuit sequencer 73 for each type of binary image data, so that each type of encoding can be performed by the same hardware.

In such a configuration, the data conversion table 33 of the sorting device 3 is set with line drawing data or line drawing data shown in FIG. 5, for example, by the external device 11. Data for line drawing is displayed by grouping the bits of each digit of the binary image data AD regardless of the digits (for example, binary image data ladder' 1010°).

is displayed as "0011"), and the line drawing data is displayed as binary image data 80 as is.

For example, the data shown in FIG.
It is set by 1. Then, in the numerical order of the addresses converted in the address conversion table 35 (+, 1., 2
．． . . . , 99), the converted data converted by the data conversion table 33 corresponding to the address is rearranged in units of bytes to obtain rearranged data ND.

For example, the data shown in FIG. 7 is set in the conversion table 74 of the encoding device 7 by the external device 11. The 4-bit rearranged data is encoded with a 5-bit code with a bit “0” added to the beginning, oooooooooo
(or +1111111) is consecutive, 1oo(
or 101), the next byte counter value at which the sequence ends is written and encoded with n (later 6) bits, and if all remaining pixels are O (or 1), the end code is 100 (or 1). ill, ).

A concrete example of the above-mentioned rearrangement and encoding is shown in FIGS. 8 and 9.

Figure 8 shows the data shown in Figure 6 (A), and Figure 9 shows the data shown in Figure 6 ([l)? This shows the case where binary image data 80 is used as shown in Figure 6 (A) or (B).
The data is rearranged into data ND in byte units in numerical order (not shown), encoded in accordance with the data shown in FIG. 7, and compressed into compressed image data GD. The data sorting shown in FIG. 6 (Δ) is a normal sorting according to one scanning direction, but the final compressed image data can be compressed to about 50% of the normal image data. Also, the 6th
The data sorting shown in Figure (B) is a sorting in which adjacent pixels are aligned in consideration of image continuity, and the final compressed image data can be compressed to about 30% of normal image data. can. Therefore, such data is not limited to that shown in FIG. 6 ([1), but may be data as shown in FIGS. 10 (A) to (C), for example.

Effects of the invention: As described above, according to the method for compressing binary image data of the present invention, it is possible to rearrange images by type for line drawings and for U4 drawings, taking into account the continuity of the images, and to encode multiple bits at a time. Therefore, it is possible to efficiently and quickly compress any binary image data such as line drawings and line drawings.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of the block configuration of an image compression device that implements the binary image data compression method of the present invention, and FIGS. 2 and 3 are block configurations of the rearranging device and encoding device, which are the main parts thereof. FIG. 4 is a diagram showing an example of a sub-block in binary image data, FIGS. 5 and 6 (
A), (B) and Fig. 1θ (A), C11)
, (C1 is a diagram showing an example of data set in the conversion table of the sorting device shown in FIG. 2, and FIG.
A diagram showing an example of data set in the conversion table of the encoding device shown in the figure, and FIGS. 8 and 9 are diagrams each showing a specific example when the method of the present invention is implemented. 1.2...Manual Huffer, 3...Sorting device, 5
．． 6... Intermediate buffer, 7... Encoding device, 8.9
...output huffer, 11...external device, 31...
Manual buffer address generator: 12.72... Ledge circuit, 33... Data conversion table, 34... Sub block address generator, 35... Address conversion table, 36... Reordering circuit sequencer , 71...
・Address generator, 73... encoding circuit sequencer,
74... Conversion table, 75... Selector, 76...
...Bit stuffing circuit.甚回甚甜曾涶子楀圀(A) (,5) (C) 蓓t. Drawing procedure amendment (method) 1. Indication of the case 1988 Patent Application No. 333840 2. Title of the invention 3. Person making the amendment Relationship with the case

Claims (1)

[Scope of Claims] 1. When one pixel is made up of one bit or a plurality of bits of binary image data, and the data is rearranged and encoded pixel by pixel, the rearranged data has the same logical value consecutively. If there is a code based on the number of continuous pixels after the predetermined code, it is encoded with a code that is added after the predetermined code, and when the same logical value is continuously present up to the end of the rearranged data, the first bit of the predetermined code is encoded. , and data other than the above is encoded with a code that has a bit different from the leading bit of the predetermined code added to the beginning of the data. Image data compression method. 2. When rearranging the binary image data pixel by pixel,
2. The method of compressing binary image data according to claim 1, wherein adjacent pixels of said binary image data are aligned.