JP2948840B2 - Rectangle extraction method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rectangle extracting method for extracting characters from a document image.

[Problems to be solved by conventional technology and invention]

As a method of extracting characters, there is a method of using vertical projection of a line image. However, in this method, when an underline is added to the character as in the example shown in FIG. 8, the break of the vertical projection becomes unclear, and it becomes difficult to detect the cutout position of the character.

There is also a method of extracting characters by extracting a circumscribed rectangle of a connected run. However, when the character touches the underline, as in the example shown in FIG.
Since the rectangle of the underline is combined with the rectangle of the character portion, it is difficult to extract characters.

With respect to such character extraction by rectangle extraction, a method of removing a group of linear elements (connected runs) if the length is equal to or greater than a predetermined length and extracting a rectangle from the remaining linear elements is disclosed in Japanese Patent Application Laid-Open No. 60-160630. -97483. However, since the line element corresponding to the underline is removed,
It is impossible to recognize underlines, and it is impossible to reproduce a document including underlines from the recognition result.

Therefore, an object of the present invention is to provide a rectangle extraction method that can separate and extract a character and a long line underline joined to the character in the case of cutting out a character to which an underline or the like is added. It is to be.

[Means for solving the problem]

The present invention extracts a run on an image, checks whether there is an existing run connected to the extracted run, and if not, generates a new rectangle surrounding the extracted run, and if so, extracts the extracted rectangle. In a rectangle extraction method of repeating a process of generating a rectangle surrounding a run and an existing run again to extract a rectangle surrounding a connected run on an image, when generating a rectangle surrounding the extracted run and an existing run, Checking whether the width of the generated rectangle exceeds a predetermined threshold value, and if not, executing the generation of a rectangle surrounding the extracted run and the existing run,
If it exceeds, a rectangle surrounding the extracted run is generated without generating a rectangle surrounding the extracted run and the existing run.

In addition, the present invention, when generating a rectangle surrounding the extracted run and the existing run, prior to checking whether the width of the generated rectangle exceeds a predetermined threshold, Check if the height of the rectangle exceeds a predetermined threshold, and if not, regardless of the width of the generated rectangle,
A rectangle that surrounds the extracted run and an existing run is generated.

(Operation)

In the rectangle extraction, if a new run that is not connected to another run is extracted, a rectangle for that run is newly generated and registered. However, if it is connected to another processed run, a new rectangle is Extend the rectangle by adding runs.
When a certain rectangle overlaps another rectangle, the rectangles are expanded by combining them.

If such expansion or combination of rectangles is executed unconditionally, the rectangles of one or more character portions of the underlined rectangles in contact with the characters will be integrated.

However, according to the present invention, by appropriately selecting the threshold value of the width (size in the line direction) of the rectangle after the expansion or integration processing, the integration of such an inconvenient underline rectangle and the character part rectangle is performed. Can be extracted and the character and the underlined rectangle can be separated and extracted, so that the extraction of the character to which the underline is added and the extraction of the underline can be respectively performed.

For the rectangle corresponding to the underline, a threshold value for the height of the rectangle is appropriately selected. If the height of the rectangle is equal to or smaller than the threshold value, the rectangle expansion or integration process is performed regardless of the result of the comparison of the width of the rectangle. By doing so, it is possible to prevent the rectangle of the underline from being divided for each run.

〔Example〕

FIG. 1 is a block diagram of a character recognition system according to one embodiment of the present invention.

The scanner 1 reads a document and stores it in the image memory 2 as binary image data. The run extracting unit 3 reads out image data of each line from the image memory 2 to extract a run which is a connection of black pixels, and sets the coordinates of the start point and the end point as run data in the rectangle extracting unit 4. Rectangle extraction unit 4
Performs registration, expansion or integration of connected run rectangles based on run data, and starts and ends (diagonal vertices) of the rectangles
Are stored in the rectangular memory 5 as rectangular data. When the process of expanding or integrating the rectangle is to be performed, the data of the width of the rectangle after the processing of expansion or integration is sent from the rectangle extracting unit 4 to the rectangular expansion / integration determining unit 6, and the processing of expansion or integration is performed. A determination is made as to whether or not to perform it, and only when a positive determination result is obtained, the rectangular data in the rectangular memory 5 is updated with the result of the expansion or integration processing.

The line cutout unit 7 determines a line cutout position based on the rectangular data obtained in the rectangular memory 5 and notifies the character cutout unit 8. The character cutout unit 8 determines a character cutout position based on the rectangular data obtained in the rectangular memory 5, and cuts out character or underlined image data from the image memory 2 in accordance with the character cutout position and the line cutout position. Send it to the unit 9 for recognition.

 The control unit 10 controls the operation sequence of each unit.

Here, the processing of the rectangle extraction unit 4 and the rectangle extension / integration determination unit 6 will be described. FIG. 2 is a flowchart of the processing, and FIGS. 3 to 5 are explanatory diagrams of the processing contents.

When the data of one run (start and end point coordinates) is set by the run extraction unit 3, the rectangle extraction unit 4 checks the connection of the runs by comparing the run data with the run data of the previous line. According to the result, it is determined whether to register, expand (add) or combine the rectangles.

FIG. 3 is an explanatory diagram of registration of a new rectangle. When a run connected to the run 21 shown in FIG.
A rectangle 22 circumscribing 21 is generated as shown in (b), and the coordinates of the start point and the end point are registered in the rectangle memory 5 as rectangle data.

FIG. 4 is an explanatory diagram of the extension of the rectangle. Since the run 25 shown in (a) is connected to the run 23 of the previous line, the run 25 is added to the rectangle 24 of the run 23 of the previous line. That is, a rectangle
24 is expanded to a rectangle 26 as shown in (b), and the rectangle data is updated.

However, prior to actually performing the expansion processing, the rectangle extracting unit 4 obtains the width W (size in the row direction) of the expanded rectangle 26 and passes it to the rectangular expansion / integration determination unit 6 to perform the rectangular expansion / integration semi-fixing. The unit 6 makes a comparison between W and the threshold value WTH. Then, when the comparison result of W <WTH (extendable) is returned, the rectangle extracting unit 4 extends the rectangle data to update the rectangle data. However, if the comparison result of W ≧ upper WTH (unexpandable) is returned, the expansion process is not performed, a new rectangle of the current run 25 is newly generated, and the run data is stored in the rectangular memory 5. sign up.

FIG. 5 is an explanatory diagram of integration of rectangles. Rectangle such as rectangles 27 and 28 shown in (a) are integrated into one. That is, the rectangles 27 and 28 are integrated into the rectangle 29 shown in FIG.

However, the width W of the rectangle 29 after integration is obtained, and the rectangle expansion / integration determination unit 6 is compared with the threshold value WTH. And W
If <WTH, rectangle integration is performed, and the contents of the rectangular memory 5 are updated with the integrated rectangular data. However, when W ≧ WTH, rectangular integration is not performed.

According to the rectangle extraction processing described above, in a line in which an underline is added to a character, for example, as shown in FIG. 6, a rectangle of a character portion (a solid white rectangle) and a rectangle of an underline (hatched). Can be extracted separately.

However, since the determination condition of the width of the rectangle is also applied to the underline rectangle, the underline rectangle is divided for each line. Such division for each line is performed in the seventh line.
This can be prevented by partially changing the processing contents as shown in the figure. In FIG. 7, the steps marked with * are applied processing steps.

That is, the height H of the rectangle after expansion or integration processing
(Size in the direction perpendicular to the row) and calculate this as the height threshold
Compare with HTH. If H ≦ HTH, the rectangle data is updated by performing expansion or integration regardless of the comparison result of the width W.

〔The invention's effect〕

As described above, according to the present invention, even when a character and an underline are in contact with each other, each rectangle can be separated and extracted, so that a character with an underline added can be reliably cut out. In addition, since the underline can be separately extracted and recognized, the original document including the underline can be restored from the recognition result.

[Brief description of the drawings]

FIG. 1 is a block diagram of a character recognition system according to an embodiment of the present invention, FIG. 2 is a flowchart of a rectangle extracting process, FIG. 3 is an explanatory diagram of registration of a new rectangle, and FIG. FIG. 5, FIG. 5 is an explanatory diagram of rectangle integration, FIG. 6 is a diagram showing an example of rectangle extraction when an underline and a character touch, FIG. 7 is a flowchart showing a modification of the rectangle extraction process, FIG. FIG. 9 is an explanatory diagram of a problem of character extraction by vertical projection, and FIG. 9 is an explanatory diagram of a problem of character extraction by rectangle extraction. 1 scanner 2 image memory 3 run extraction unit 4 rectangle extraction unit 5 rectangle memory 6 rectangle expansion / integration determination unit 7 line segmentation unit 8 ... character cutout part, 9 ... recognition part.

Claims (1)

(57) [Claims] 1. A line on an image is extracted, and the presence or absence of an existing run connected to the extracted run is checked. If there is no line, a rectangle surrounding the extracted run is newly generated. In the rectangle extraction method of extracting a rectangle that surrounds a connected run on an image by repeating the process of generating a new rectangle and a rectangle that surrounds the existing run, there is an existing run that is connected to the extracted run. When generating a rectangle surrounding the run and the existing run, determine whether the width of the generated rectangle exceeds a predetermined threshold,
If it does not exceed, execute the generation of a rectangle surrounding the extracted run and the existing run, and if it does, generate the rectangle surrounding the extracted run and the existing run without enclosing the extracted run. Processing for generating a rectangle, and generating a rectangle surrounding the extracted run and the existing run, prior to checking whether the width of the generated rectangle exceeds a predetermined threshold, Checking whether the height of the rectangle exceeds a predetermined threshold, and if not, performing a process of generating a rectangle surrounding the extracted run and an existing run, regardless of the width of the generated rectangle; A rectangle extraction method characterized by comprising: