JPS58106665A - Character line cutout method - Google Patents

Abstract

PURPOSE:To cut out character lines having a large slope surely, by splitting a document picture into blocks, obtaining the projection of each block toward the character line direction and checking the connection of the projections of each block. CONSTITUTION:According to an address control of a R/W control circuit 103, a picture data in a buffer memory device 101 is read out from a head line sequentially. In case of character cutout, a document picture is split into >=3 blocks toward the character line direction. A projection detecting circuit 104 checks whether or not black picture elements exist for a prescribed number or over at each block and detects the projection toward the character line direction at each block. When the detection of projection is finished, a connection discriminating circuit 105 checks the connection of projections and cuts out the character line. First, the overlapping between the projection of a block and an adjacent block is checked and the overlapped projections are connected. This operation is done for all the projections.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for cutting out character lines on a document image.

In optical character recognition devices, etc., before extracting individual character turns from a read document image,
It is necessary to cut out character lines.

This text line extraction is usually done in the text line direction (
This is done by taking one projection in the horizontal direction for a horizontally written document, and in the vertical direction for a vertically written document. but,
If a character line is tilted or the skew of the document is large, the projection will expand by the tilt, making the extraction of the character line inaccurate. If the skew becomes even larger, the projections of adjacent character lines will overlap, making extraction impossible.

To solve this problem, for example, the horizontal projections are obtained for the left and right edges of a horizontally written document image, and black pixels are counted by scanning diagonally from the center of each projection. A method of cutting out a character line by detecting the scanning direction in which the number of black pixels is maximum as the direction of the character line has also been proposed. However, this method tends to require complicated algorithms and device configurations, such as the need for diagonal running. Furthermore, there is a risk that a short character line sandwiched between long character lines with a large slope and a large number of black pixels may fail to be extracted.

An object of the present invention is to provide a new method for cutting out character lines that can more reliably cut out character lines with large inclinations than before.

Another object of the present invention is to provide a character line extraction method that has a simple extraction algorithm, does not require a large storage area, and is easy to implement.

Therefore, the character cutting method of the present invention divides a document image into three or more blocks in the character line direction, and scans the document image for each block in the character line direction (horizontal direction for horizontal writing documents, vertical writing direction). For documents, Tari IP-/J IHJ J
v) 2u Glaze Yako αノ, L Rimi) i: C'C seeking meta This is characterized by cutting out individual character lines on the document image by examining the connections between the projections of each block. be.

Hereinafter, the present invention will be specifically explained using an example.

FIG. 1 is a block diagram showing an example of an apparatus for executing character line segmentation according to the present invention.

Reference numeral 50 denotes an image memory in which image data for one or more pages of a document is stored. Reference numeral 101 denotes a buffer memory device used as a storage area for cutting out character lines, and has a capacity capable of storing image data of the number (N) of scanning lines corresponding to one character line with the highest inclination.

Reference numeral 102 denotes an image detection circuit that detects a scanning line containing an image. In this example, in order to avoid the influence of noise, a scanning line in which two or more black pixels are consecutive is detected as an image line. 103 is a buffer memory device 101 read/write (
This is a R/W control circuit that controls f(,/W). 104 is a projection detection circuit, and 105 is a connection judgment circuit for identifying the shairi-shai-ayu-r-dou (also, the touch).

Next, the operation of cutting out character lines will be explained using a horizontally written document image as conceptually shown in FIG. 2 as an example.

The /W control circuit 103 requests the image memory device 5o to transfer image data from the top of the document. Image data read from the image memory device 50 is sequentially written into the buffer memory device 101 under the control of the R/W control circuit 103, but is also input to the image detection circuit 102 at the same time.

When the image detection circuit 102 detects the first image line and outputs a signal, the 几/W control circuit 103 sets the scanning line as the first line t1 (FIG. 2), and then selects the last line tN (second line) of the N main line. When the image data shown in the figure) is read into the buffer memory device 1o1, a request is made to stop the transfer of image data between the image memory devices. This results in
N of scanning lines t1 to tN is stored in the buffer memory device 101.
912 minutes of image data is accumulated. Note that the image data of the scanning lines before the first line t1 are discarded.

When the buffer memory device 101 becomes full in this way, the image data stored therein is scanned and a character line cutting operation is started.

That is, according to the address control of the R/W control circuit 103, the image data in the buffer memory device 101 is sequentially read out from the first line t1.

At this time, the scanning line number (relative line number from the first line t1) being read out and the block number are sent from the L/W control circuit 103 to the projection detection circuit 104.

Here, block numbers will be explained.

In the present invention, when cutting out characters, a document image is divided into three or more blocks in the character line direction. In this example, the document image is divided into seven blocks N to G, as shown by dotted lines in FIG. The identification numbers of these blocks N to G are the above-mentioned block numbers.

The C1 projection detection circuit 104 uses buffer memory 1. I'4
For each scanning line read from f101, a number of digits are placed in each block, and a projection in the character line direction (main scanning direction) is performed for each block. To detect. The projections obtained for each block in this way are shown in FIG. 2 by the vertical arrows a1. b1°...11 is conceptually shown. In addition, blocks B and C.

In a block such as E where there are two character lines, it is natural that two projections are detected in the same block. The projection detection circuit 104 detects and holds the scanning line numbers of the upper and lower ends of each projection detected for each flick.

When the projection detection described above is completed, the connection determination circuit 105 examines the connection between the projections and cuts out a character line. First, the overlap between the projection of each block and the projection of its neighboring block is checked, and the overlapping projections are connected.

This operation is performed for all the projections of 'C'.

In the example of FIG. 2, the projection f1+ of adjacent blocks F and G
Since the common scanning line is included in the range of 'l, the projection f1+
'l is concatenated. The projections e1+h of blocks E and F include a common scanning line, so they are interconnected, and therefore the C projections e1+r1+ 91 are interconnected. Projection d1 of block D and projection e1 of block E do not overlap, so they are not connected.

In this way, in the example of C1 in FIG. 2, projection a1. b1゜C
1, -projection eII fII21, projection b2I021dl
, C2 are each connected as a group.

Next, the connection between the connected projection group including the projection including the leading line t1 and other projection groups (or isolated projections) is examined. If the projection group including the first line contains the projections of all blocks, it is determined that there is a character line within the range of the projection group. A strip-shaped area is cut out as a character line, and information indicating the area is output.

If the projection group including the leading line t1 does not include projections of all blocks, another projection (group) that intersects with the extension of the straight line connecting the centers of the left and right projections in the projection group is searched. If it exists, its projection(s) and the first line t1
, and a straight line passing through the center of the left and right projections is used as a reference, and a band-shaped area of a constant width is cut out as a character line. If there are no other projections (groups) to be connected, use a straight line passing through the center of the left and right projections in the projection group including the first line t1 as a reference, and define a character line as a strip area of a constant width C.
break the ice.

In the example in Figure 2, the character string (00...00,11
1...111) will be cut out.

When you finish cutting out one character line as above,
The /W control circuit 103 erases (clears) the image data in the C buffer memory device 101 for the area cut out as a character line. Next, the L/W control circuit 103 redefines the scanning line at the upper end of the projection at the highest position in the non-erased range as the leading line t1'. In the example shown in FIG. 2, the scanning line at the upper end of the projection e2 is new and is set as the first line t1'. Then, the CR,/W control circuit 103 requests image data to be transferred between the image memory devices from the scan line next to the last scan line transferred previously.・
When the image data for N scanning lines from the first line t1' is accumulated in the rough area memory device 101, the R/W control circuit 103 requests the image memory device 50 to stop transferring the image data. Thereafter, a character line cutting operation similar to that described above is started.

By repeating the above operations, all 'C' character lines on the document image are cut out.

In the above explanation, the image data ( ) (in the Turahua memory area 101) of the area cut out as a character line is cleared, but instead of doing this, the projection in that area is used as the concatenation target for subsequent character cutting. It is also possible to perform processing such as excluding the data from UNQ.It is also possible to perform projection detection and connection determination in parallel.

Since the present invention has been described in detail above, it is possible to reliably cut out a character line with a large inclination or a short character line sandwiched between long character lines, and the extraction algorithm is simple and can be used to cut out a large volume. Since no storage area is required, the cutting device can be realized at a low cost, and has extremely large effects.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention, and FIG. 2 is a block diagram for explaining the character extraction process. Seki: Image memory device, 101: No.Z buffer memory device for character extraction, 102: Image detection circuit, 1
03...R/W (read/write) control circuit, 104...
- Projection detection circuit, 105... connection determination circuit. Agent Patent Attorney Makoto Suzuki

Claims (1)

[Claims] ■ Divide the document image into three or more blocks in the text line direction, scan the document image, find the projection in the text line direction for each block, and connect the obtained projections of each block. 1. A method for cutting out character lines, the method comprising cutting out individual character lines on the document image by examining the character lines.