JPH0217766A - Data compression system - Google Patents

Abstract

PURPOSE:To improve compressibility by setting input image data having a larger number of white lines out of the input image data and the input image data in which the input image data is rotated by 90 deg. as data compression targeted data. CONSTITUTION:The digital data of an input image outputted from a scanner 3 is stored in a page buffer 2. Next, the digital data is rotated by 90 deg. by a 90 deg. rotating apparatus 4, and is stored in another area in the page buffer 2. The number of white lines is counted by making access so as to set those two pieces of data in the same scanning direction. And the data is read out from a memory area having a larger number of white lines, and data compression is applied on it by a data compressor 5, then, it is stored in a compression data file 6. In such a way, it is possible to decide the vertical write or the horizontal write of a document and to decide a direction of main scan and to improve the compressibility.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a data compression method, and in particular,
The present invention relates to a data compression method suitable for improving data compression rate by determining horizontal writing during scanning.

[Conventional technology]

When transmitting image data, reduce the amount of transmitted information,
In order to improve the transmission speed, data compression is performed using techniques such as encoding.

Taking encoding as an example, after quantizing and sampling input image data scanned by a scanner etc., the lengths of white and black of the sampled image data are determined according to a predetermined code table. encoded based on

Here, general documents have vertical and horizontal writing, but in the past, it was common for documents to be scanned only in a predetermined direction using a scanner or the like.

Regarding data compression, for example, see Kubota, "Facsimile and New Image Communication" (Sanpo Publishing, 1983), 67-
It is described in detail on page 77.

[Problem to be solved by the invention]

However, as mentioned above, if a document with vertical or horizontal writing is scanned in only one direction.

There is a problem in that the compression ratio varies greatly depending on whether the original is written vertically or horizontally.

That is, when compressing image data, the more white lines (scan lines) there are, the better the compression rate will be. For example, as shown in FIG. 4, when scanning in the horizontal direction, the compression ratio is higher in horizontal writing (a) than in horizontal writing (,) and vertical writing (b).

The present invention has been made in view of the above-mentioned circumstances, and its purpose is to solve the above-mentioned problems in the conventional technology, automatically distinguish between vertical writing and horizontal writing of a single document, and to automatically determine the direction of main scanning. The object of the present invention is to provide a data compression method that makes it possible to improve the compression rate by determining the .

[Means for resolving levy]

The above-mentioned object of the present invention is to provide a data compression method for compressing input image data, with respect to the input image data and the input image data obtained by rotating the input image data by 90''.
A data compression method characterized in that the number of white lines is counted and compared, and the input image data with a larger number of white lines is selected as the data to be compressed, or the input image The number of white lines is counted and compared by accessing the memory storing data in two directions perpendicular to each other, and the input image data in the access direction with the larger number of white lines is data-compressed. This is achieved by a data compression method characterized by using target data.

[Effect]

As described above, when compressing one image data, the more white lines (scanning lines) there are, the better the compression rate will be.

Therefore, in the image data compression method according to the present invention,
If necessary, the image is rotated by 90 degrees to always align the scanning direction with the vertical or horizontal writing direction of the document.

To this end, in the image data compression method according to the present invention, scan data is scanned in two scanning directions perpendicular to each other, and the number of white lines is checked to determine whether the document is written vertically or horizontally. It is something.

By reading the data and compressing it according to the vertical/horizontal writing direction of the document determined in this way,
The effect is that it is always possible to perform the most effective data compression.

〔Example〕

Hereinafter, five embodiments of the present invention will be described in detail based on the drawings.

FIG. 2 is a block diagram of an apparatus showing an embodiment of the present invention. In the figure, 1 is the CPU that controls the entire device.
, 2 is a page buffer for storing image data read by the scanner 3; 4 is a 90° rotator for rotating the image data stored in the page buffer 2 by 90°; 5 is a data compressor for compressing data; 6 indicates a file that stores compressed data.

FIG. 3 is a diagram showing the configuration of a document vertical/horizontal writing determination unit 20, which is a main part of this embodiment. The main vertical writing/horizontal writing discriminator 20 includes a white line discriminator 21 and a white line counter 22. This is the main operation of the white line discriminator 21. The counting of the number of white lines and the action based thereon are realized by the operation of the CPUI based on a program stored in a memory (not shown), as will be described later.

An outline of the operation of the vertical writing/horizontal writing discriminating unit 20 is as follows. That is, the digital data (scanner signal) output from the scanner 3 is discriminated and counted by the white line discriminator 21 for each main scan, and if the white data is larger than a predetermined setting value, the white line is detected. It is determined that this is the case, and a white line signal is output. This white line signal is counted by a white line counter 22. At the end of scanning, read this value and determine whether the target document is written vertically or horizontally, that is, whether or not to perform 90' rotation.
Discern.

FIG. 1 shows the operation flow of the white line discriminator 21. The operation will be explained in detail below based on FIG.

First, digital data of an input image output from the scanner 3 is stored in the page buffer 2 (step 11). Next, the 90° rotator 4 reads the data from the page buffer 2 and rotates it by 90' (
Step 12), and store it in another area of the page buffer 2 (Step 13).

Two pieces of data stored in different areas of the page buffer 2 are accessed in the same scanning direction, and the number of white lines is counted (step 17I).

Based on this result, data is read from the memory area with the larger number of white lines, data is compressed by the data compressor 5, and the obtained compressed data is stored in the compressed data file 6 (steps 15 to 7). ).

As shown in the figure, the operation of counting the number of white lines is performed as an operation of the CPU using the work area.

As a result, it is possible to automatically determine whether the document is written vertically or horizontally and determine the direction of main scanning, thereby realizing data compression that improves the compression rate.

In the first embodiment, input image data and input image data obtained by rotating the input image data by 90c' are stored in different areas of a page buffer, and these are scanned in the same scanning direction. An example has been shown in which the number of own lines is counted and compared, and the input image data with a larger number of white lines is selected as the data to be compressed.

The present invention is not limited to this. For example, the memory storing the original input image data may be accessed in two directions orthogonal to each other,
It is also possible to use a method in which the number of own lines is counted and compared, and the human-generated image data with the larger number of white lines among the two access directions is set as the data to be compressed.

In this case, as in the embodiment shown above, it is possible to automatically determine whether the document is written vertically or horizontally and determine the direction of main scanning, making it possible to improve the compression ratio. Data compression can be achieved.

The above embodiments are given as examples of the present invention, and the present invention also includes embodiments other than these. For example, the counts of steps 14 to 17 shown in FIG.
The operation based on the determination may be performed by hardware instead of software.

〔Effect of the invention〕

As described in detail above, according to the present invention, in a data compression method for compressing input image data, the number of white lines is reduced for the input image data and the input image data obtained by rotating the input image data by 90 degrees. After counting and comparing, the input image data with a larger number of white lines is selected as the data to be compressed, or the access directions to the memory storing the input image data are orthogonal to each other. By counting and comparing the number of white lines in two access directions, and selecting the input image data in which the number of white lines is larger among the two access directions as the data to be compressed, the document can be written vertically or horizontally. By automatically determining the main scanning direction and determining the main scanning direction, this method has the remarkable effect of realizing a data compression method that can improve the compression rate.

[Brief explanation of the drawing]

FIG. 1 is an operation flowchart of the white line discriminator which is the main part of the present invention, FIG. 2 is a block configuration diagram of the double hit of the embodiment,
FIG. 3 is a diagram showing the configuration of a document vertical/horizontal writing determination unit;
FIG. 4 is a diagram for explaining the relationship between the scan direction and the compression ratio. 1: CPU, 2: Page buffer, 3: Scanner, 4:
90" rotator, 5: data compressor, 6: compressed data file, 20: vertical/horizontal writing discriminator, 2N white line discriminator, 22: white line counter.

Claims (2)

[Claims] (1) In a data compression method for compressing input image data, the number of white lines is counted and compared for the input image data and input image data obtained by rotating the input image data by 90 degrees, and A data compression method characterized in that input image data having a larger number of white lines is selected as data to be compressed. (2) In a data compression method for compressing input image data, the number of white lines is counted and compared while accessing the memory storing the input image data in two directions perpendicular to each other, and Of these,
A data compression method characterized in that input image data with a larger number of white lines is used as data to be compressed.