JP3177138B2 - Extraction method of drawing closed area - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for automatically extracting a closed area from handwritten or printed drawing information input via an image scanner or the like. The present invention relates to a method for extracting a closed region of a drawing, which has a line segment limited to several types as a basic configuration, and is capable of extracting a closed region formed by the line segment even if there is faint or broken lines or noise.

[0002]

2. Description of the Related Art When automatically recognizing a handwritten or printed drawing, it is necessary to perform a process of extracting a line segment or a closed region constituting the drawing. As a method of extracting a closed region, a method of tracking a boundary point inside or outside the region has been used. However, in the conventional boundary point tracking technology, there is a problem that, due to the presence of blurred or broken lines, adjacent separate regions are combined and extracted as one region, or cannot be extracted as a closed region.

[0003]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems in the conventional method of extracting a closed region of a drawing, and is applicable not only to a correctly printed drawing but also to a handwritten drawing having many faint lines and cuts. It is an object of the present invention to provide a new closed region extraction method that can be used.

[0004]

According to the method for extracting a closed region of a drawing of the present invention, in order to solve the above-mentioned problems, (1) raster data obtained through an image scanner or the like is converted into a line segment start / end pattern; And (2) a method of performing contour tracing using a start / end point pattern and extracting a closed region.

FIG. 1 is a diagram showing a processing flow of the present invention. In FIG. 1, reference numeral 10 denotes a pattern map creation process;
0 indicates the process of the closed area abstraction process. When the drawing information of the binary data is input, the pattern map creation processing 10 searches for line segments in each direction on a grid line extending in a plurality of directions from a grid intersection on a sheet on which a grid-like auxiliary line is printed. Set an area and set this search area perpendicular to the direction of the line segment
Scans one row at a time in any direction, and has one or more black pixels
Is determined by whether or not the number exceeds a predetermined threshold.
It is determined whether a line segment exists in the direction (S1).
1) A code is assigned according to the presence or absence of a line segment, a state pattern of grid intersections is determined by a combination of existing line segments in each direction, and a state pattern is determined for all grid intersections to create a pattern map (S12). ) Process.

The closed area extraction processing 20 finds the start point of the closed area search from the pattern map (S21), determines the next point from the grid intersection pattern of the start point based on the priority in the next direction, and determines the next route. (S22), the determined route is taken as the contour of the closed area (S23), and the closed area is extracted.

The state pattern of each grid intersection is, for example, a code including digits (bits or bit groups) corresponding to the number of line segments of the grid line extending from the grid intersection, and each code in the code corresponding to each line segment. The position of the digit is represented by a code determined so as to be in the order of the direction of a line segment appearing counterclockwise or clockwise from a predetermined direction. The priority order of the search directions in the route search is determined according to the order of the digits in order from the digit position next to the digit of the known route direction in the code representing the state pattern.

In the pattern map creation processing 10 of the present invention, a pattern map of a state pattern for each grid intersection is created using the start and end point patterns of the line segment. Can be reduced.

In the closed region extraction processing 20, the connection of the line segment between the grid intersections is determined using the pattern map. Effects can also be ruled out. In addition, the priority of the contour route search direction is
By making it possible to determine according to the arrangement of the digits (bits or bit groups) of the codes assigned to the state patterns, it is possible to realize an efficient search using simple logic.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for extracting a drawing closed area according to the present invention is a logical circuit drawing showing circuit wiring created using a sheet on which grid-like auxiliary lines are drawn, and a floor plan showing a spatial layout of a floor plan. It can be used for automatic extraction processing of a closed region in various drawings such as.

FIG. 2 is a diagram showing an example of grid-like auxiliary lines written in dropout color or the like on a sheet for writing those drawings. These auxiliary lines are parallel lines drawn at equal intervals in several directions so that intersections are made at equal intervals. FIG. 2A shows two vertical and horizontal directions.
FIG. 2B shows auxiliary lines of a 45-degree diagonal left and right direction.

Hereinafter, as one embodiment of the present invention, a case where the present invention is applied to extraction of a closed region in a floor plan will be described. Usually, vertical and horizontal lines as shown in FIG. 2A are drawn at regular intervals as reference lines on a sheet dedicated to the floor plan. The reference line on this drawing is called a grid line, and the intersection of the reference lines is called a grid intersection.

The size of many elements (walls, fittings, tatami mats, stairs, etc.) constituting the floor plan is expressed by an integral multiple of the interval between grid lines. For this reason, when drawing a floor plan on this special paper, most line segments are written on grid lines, and the start and end points of the line segments are written on grid intersections. The method for extracting a closed region according to the present invention utilizes this feature, and the condition that a line segment forming a drawing element is written on a grid line is a writing condition, and a line segment forming a drawing element written on the grid line is used. Let the closed region created by be an extraction target.

The processing procedure of the present invention shown in FIG. 1 will be described in detail. The input binary raster data is converted into the pattern map of the present invention in the pattern map creation processing 10, and then the outline of the closed area is searched for in the closed area extraction processing 20.

First, the pattern map creation processing 10 will be described. The pattern map is data in which a state of a line passing through a grid intersection on a drawing is matched with a state pattern of a previously prepared line, and a pattern code of an appropriate state pattern is recorded. The floor plan drawn by hand is converted into raster data obtained via an image scanner, and a pattern map is generated therefrom.

The pattern code used at this time, when converted into a binary number, corresponds to each digit and each direction extending from the grid intersection. That is, the digit of the pattern code corresponding to the direction in which the line segment exists is set to 1, and the digit corresponding to the direction in which the line segment does not exist is set to 0.

For example, as shown in FIG. 3, in a pattern extending from the grid intersection in four directions, the pattern code is 2
4 digits in hexadecimal notation, N direction (upward) is the first digit,
The E direction (right direction) is the second digit, and the S direction (downward) is the third digit.
The W direction (left direction) corresponds to the fourth digit. If there are line segments written in all of these directions, all the corresponding digits are 1 (1,1,1,1).

In the drawing used in the present embodiment, if the printed grid lines are of two types, that is, the horizontal direction and the vertical direction, the grid intersection pattern has 16 patterns as shown in FIG. is there. In the determination of the state pattern, the presence or absence of a written line segment is determined in four directions, up, down, left, and right, with the grid intersection in the drawing as the center, and the pattern is determined by a combination of existing line segments.

FIG. 5 is a diagram for explaining an example of a method for determining the presence or absence of a line segment near a grid intersection. FIG. 5 (A)
Indicates a grid intersection for which the presence or absence of a line segment is to be determined.
As shown in FIG. 5B, a search area for line segments is set in four directions around the grid intersection near the grid intersection. This area is scanned one column at a time in the direction perpendicular to the direction of the line segment, and the column where the black pixel exists is set to 1 and the column not existing is set to 0. As a result of scanning all the columns in this manner, when the column which becomes 1 exceeds a certain threshold value, it is determined that a line segment exists.

FIG. 5C shows the proportion of black pixels in each direction. Here, assuming that the threshold is 4/7, the upper, right,
It is determined that the line segment exists in the lower three directions and does not exist only in the left direction. As a result, the grid intersection shown in FIG. 5A is one of the 16 grid intersections shown in FIG.
It is determined to be pattern 7, and a pattern code [0111] is assigned. Thus, a pattern map is created by determining a pattern and assigning a pattern code for all grid intersections.

FIG. 6 shows an example in which handwritten drawing data is converted into a pattern map. A state pattern is determined for all grid intersections in the drawing data shown in FIG. It is determined that the grid intersection P1 matches the pattern 6 among the grid intersection patterns shown in FIG. 4, and “6” is stored at the position of the grid intersection P1 in the pattern map. Similarly, it is determined that the grid intersection P2 matches the pattern A among the grid intersection patterns shown in FIG. 4, and “A” is stored at the position of the grid intersection P2 in the pattern map. By performing this processing for all grid intersections, a pattern map as shown in FIG. 6B is obtained.

FIG. 7 is a processing flowchart of the pattern map creation processing. In FIG. 7, in step S31, a line segment search area of a predetermined size is set on a grid line from a grid intersection.

In step S32, the presence or absence of a line segment in the search area in each direction is determined by the method described with reference to FIG.
In step S33, a state pattern is determined from a combination of directions in which the line segment exists, based on the determination result of the presence or absence of the line segment.

In step S34, a value (pattern code) indicating the determined state pattern is stored at the position of the corresponding grid intersection on the pattern map. Step S35
It is determined whether or not the processing for all grid intersections has been completed, and if not, step S3
Returning to step 1, the same process is repeated. When the processing has been completed for all grid intersections, the pattern map creation processing ends.

The feature of this pattern map creation process 10 is that pattern-coded data is created for all grid intersections on the drawing as shown in FIG. 6, and that each pattern code is slightly different as shown in FIG. In order not to be affected by the interruption or blurring of the line, it is necessary to check and find the pixels in a certain range, and each digit when the pattern code is expressed in a binary number, as shown in FIG. This corresponds to the state of the line segment in the direction.

Next, the closed region extraction processing 20 will be described. The closed region extraction process 20 is a process of searching for a boundary point of a drawing closed region using the pattern map generated in the pattern map creation process 10 earlier.

In the procedure, first, a starting point candidate is found from the pattern map. Next, based on the state pattern of the grid intersection at the start point, the next grid intersection on the contour of the closed area is determined based on the priority of the route search direction to the next point. At this time, if the state pattern of the next grid intersection does not include a line segment in the direction (direction of the previous intersection) with respect to the direction in which the line segment has advanced, the line segment is considered to be continuous. Since it cannot be said, the confirmation processing is performed. Further, the next route is similarly determined one after another. When the path returns to the start point, a path representing the outline of one closed region is extracted. If there are other starting point candidates on the drawing,
The above processing is repeated in the same manner with the grid intersection as the second starting point.

In this embodiment, the state pattern of the grid intersection as the search start point is set to four patterns 6, 7, E, and F among the state patterns shown in FIG. If there is a code, the grid intersection is set as the search start point. The search direction from the start point is rightward. As for the subsequent route search, as shown in FIG. 8, a leftward priority is given to the traveling direction of the route (right direction, straight traveling direction, left direction, backward direction).

At this time, since each digit of the binary-converted pattern code indicates the direction in which the line segment extends, the route search can be performed by the following processing. The correspondence between each digit and each direction is as shown in FIG.

A specific description will be given based on the drawing data shown in FIG. As the raster scan is performed from the upper left of the drawing data, the grid intersection P1 (pattern 6) is picked up as the first start point. Since the traveling direction of the route search from the start point is the right direction, the candidate for the second point is the grid intersection P2.

Here, the connection state between the grid intersections P1 and P2 is checked. Whether the connection is made is determined by setting the grid intersection P1 as the start point and the grid intersection P2 as the end point.
Judgment is made based on whether or not the pattern on the end point has a line extending in the direction of the start point. That is, since the start point P1 is located at the position in the W direction (left) in FIG. 3 with respect to the end point P2, if a line segment exists at this position in the W direction in the state pattern of the grid intersection P2, the grid intersection P1 and the grid intersection P1 It is determined that the intersection P2 is connected. As shown in FIG. 3, since the position in the W direction (left) corresponds to the fourth digit in the bit string, if the fourth digit of the pattern code is 1, a line segment exists.

Here, since the pattern code of the grid intersection P2 is A (= 1010), it is determined that the grid intersection P1 and the grid intersection P2 are connected. As a result, the grid intersection P2 becomes the second point. After the third point,
As shown in FIG. 8, the candidate points are determined in the direction of the priority in the counterclockwise direction from the next in the backward direction (to the right with respect to the traveling direction).

In terms of the bit sequence of the pattern code, the left-hand priority of the route search is expressed in the fourth digit → the third digit →
The second digit → the first digit → the fourth digit →... (However, the highest priority digit is a digit to the right with respect to the traveling direction). That is,
As for the priority, the digit shifted to the right with respect to the digit indicating the traveling direction has the highest priority. At the grid intersection P2 of the second point (pattern A = 1010), the grid intersection P which is the starting point
Since the traveling direction from 1 (pattern 6 = 0110) is the fourth digit, the next highest priority is the third digit (S direction). The grid intersection P2 of the second point is pattern A = 1010, and the third digit of the pattern code is 0.
Therefore, we cannot proceed in this direction. The direction with the next highest priority is the second digit, and since this digit is 1,
Proceeding to the second digit, that is, the direction E (rightward direction) in FIG. 3, the third point candidate is set as the grid intersection P3.

In the same manner as above, the connection state between the grid intersections of the second point and the third point is checked. Since the grid intersection P2 of the second point is in the W direction (left) when viewed from the grid intersection P3, the fourth digit is checked by the bit string expression of the pattern code in the same manner as described above. Since the grid intersection P3 has the pattern E = 1110, the fourth digit is 1, and it is determined that the grid intersection P3 is connected. Further consider the fourth point candidate. At the third point, the traveling direction from the second point is the fourth digit, so the direction with the highest priority is the third digit.
Since the grid intersection P3 has the pattern E = 1110 and the third digit is 1, a line segment exists, and this direction is selected as the first search direction of the fourth point. This route search is repeated, and the search ends when the start point is reached. Subsequently, the next start point is searched, and a route search for extracting a closed region is performed in the same manner.

FIG. 9 is a processing flowchart of the closed area extraction processing. In step S41, a search start point is detected from the pattern map, and is set as a grid intersection Ps to be processed.

In step S42, the next grid intersection Pe is determined from the current state pattern of the grid intersection Ps according to the priority of the search direction of the route to the next point. In step S43, the current grid intersection Ps and the next grid intersection Pe are determined from the state pattern of the next grid intersection Pe.
Check the existence of a line segment between and.

In step S44, it is determined whether or not the existence of the line segment has been confirmed.
Proceeds to the process of step 45, and if it cannot be confirmed, step S4
Returning to step 2, the route is searched for the search direction of the next priority.

In step S45, a line segment between the two grid intersections Ps and the grid intersection Pe is set as a path, and the grid intersection Pe is set as the next grid intersection Ps to be processed. In step S46, it is determined whether or not the grid intersection Ps is a search start point. If the grid intersection Ps is the start point of the search, the process of step S47 is performed. If the grid intersection Ps is not the start point, the process returns to step S42.

In step S47, the determined route is extracted as the contour of the closed area. In step S48, it is determined whether or not there is another start point candidate. If there is another start point candidate, the process returns to step S41 to repeat the same processing.
If not, the process ends.

The feature of this closed region extraction processing 20 is that, as shown in FIG. 8, the search priority in the next direction is a fixed order counterclockwise (or clockwise) with respect to the traveling direction.
Use the pattern code on the pattern map to check for the presence or absence of a line segment and search for a route. Since the closed area is searched using the pattern code, the line is not affected by breaks or blurring between line segments. , Each digit of the pattern code corresponds to a line segment in each direction of the grid intersection, as shown in FIG. 3, so that the next direction search is easy.

As described above, in the present invention, since the closed area search is performed using the state pattern of the grid intersection, the closed area can be extracted without being affected by the cut or blur in the middle of the line segment.

[0042]

According to the present invention, the meandering of the handwritten line is corrected by the pattern map creation processing.
Line breaks and blurring can be reduced. Further, the closed region extraction processing makes it possible to reduce the influence of noise other than the line segment forming the contour of the closed region while reducing the influence of line breaks or blurring, thereby improving the accuracy of the closed region extraction processing.

Further, the pattern code indicating the state of the grid intersection is represented by a sequence of digits determined in consideration of the search priority in the next direction, with each digit corresponding to the direction of each line segment. Direction search can be performed easily and efficiently.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating the flow of processing according to the present invention.

FIG. 2 is a diagram illustrating an example of an auxiliary line written on a drawing sheet.

FIG. 3 is a diagram illustrating an example of pattern coding of grid intersections.

FIG. 4 is a diagram illustrating an example of a state pattern of a grid intersection;

FIG. 5 is a diagram illustrating an example of a method for determining the presence or absence of a line segment near a grid intersection;

FIG. 6 is a diagram showing an example of a pattern map.

FIG. 7 is a processing flowchart of a pattern map creation process.

FIG. 8 is a diagram illustrating the priority order of the route search directions.

FIG. 9 is a processing flowchart of a closed region extraction process.

[Explanation of symbols]

 10 Pattern map creation processing 20 Closed area extraction processing

──────────────────────────────────────────────────続 き Continuation of front page (58) Field surveyed (Int. Cl. ⁷ , DB name) G06T ^7/ 00-7/60

Claims (1)

(57) [Claims] 1. A method for extracting a closed area of a handwritten or printed drawing on a sheet on which grid lines are printed, comprising: a line segment extending in a plurality of directions from a grid intersection in each direction. A search area is set, and pixels are scanned one by one in the search area in a direction perpendicular to the direction of the line segment. Whether or not the number of columns having one or more black pixels exceeds a predetermined threshold value wherein determining whether a line segment exists for each direction, the assigned codes according to whether or not the line segment, glyceryl
From the number of digits corresponding to the number of grid lines
Each digit of the number of digits is a grid line segment in a predetermined direction.
To grid lines that appear counterclockwise or clockwise from
The state pattern of the grid intersection composed of
Set the code assigned according to the presence or absence
And determining a state pattern for all grid intersections to create a pattern map; and searching the pattern map for a predetermined state pattern.
Start grid intersection Ps with state pattern that matches
A point, counterclockwise from the digit corresponding to the line segment in the predetermined direction
Or, according to the clockwise priority, the grid intersection Ps
Find the next grid intersection Pe by searching the state pattern
In the state pattern of the grid intersection Pe,
Line segment exists at the digit position corresponding to the direction of grid intersection Ps
Check if it does
Search the route of the state pattern of Ps from the next priority digit.
To find the grid intersection Pe and confirm it
The above grid intersection Pe as a new grid intersection Ps
Whether the new grid intersection Ps is the starting point of the search
It is determined that the new grid intersection Ps is the starting point of the search.
If not, the state pattern of the new grid intersection Ps
Of the digit position corresponding to the direction of the grid intersection Ps
The route is searched from the digit of the next priority and the next grid intersection P
e, and the new grid intersection Ps is searched.
Extracting the determined path as the contour of the closed area if the start point is a start point of the drawing.