JPH06139360A - Line types recognizing method and device - Google Patents

Abstract

PURPOSE:To improve the recognition ratio of line types recognition by enabling the continuation of line segment trace in a branch point, in the line types recognition technique in a drawing input device. CONSTITUTION:A system confirms the non-branch/branch of a reference point (S2). In the case of the non-branch, other non-branch points are retrieved (S3). Whether the connection of the vector of the non-branch point which is found is possible or not is decided (S5). When a connectable vector does not exist, a branch point is retrieved within a prescribed area (S8). Whether the connection of each vector of the branch point which is found is possible or not is decided (S10). When the reference point is the branch point, whether the connection of each branch vector to be connected with the reference point is possible or not is decided. When a vector which is possible to be connected does not exist, whether a connection error vector candidate exsists for the branch vector is confirmed. When the candidate exists, whether the connection of the branch vector of the trace destination side of the connection error vector candidate is possible or not is decided. When the vector which is possible to be connected does not exist, the non-branch point is retrieved. Whether the connection of the vector of the non-branch point which is found is possible or not is decided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for recognizing characters, figures, etc. from an image such as a handwritten drawing, and more particularly to a line segment tracking function improved and line type recognition accuracy improved.

[0002]

2. Description of the Related Art A hardware configuration of a drawing automatic input device is shown in FIG. The image scanner 1 optically reads a handwritten drawing or the like. The binary image input interface 2 takes in binary image data from the image scanner 1. The image memory 3 stores binary image data. The image processor 4 converts binary image data into vector data. A disk 5 is controlled by the disk controller 6. Reference numeral 7 is a system memory, 8 is a host system connection interface for communicating with a host system such as a CAD (Computer Aided Design) system and a mapping system, 9 is a host processor that performs the main control of this system, and each system unit is It is connected to the host processor 9 via the system bus 10.

An outline of the operation of this device is shown in FIG. The binary image input interface 2 takes in the binary image data read by the image scanner 1 and transfers / stores it in the image memory 3 (S1). After that, the image processing processor 4 performs the image processing on the binary image data by the thinning method or the contour detection / skeletonization method. In the case of the contour detection and skeletonization method, a contour pixel string is extracted from the binary image data to generate a contour vector (S2), and further, a skeleton vector corresponding to the center line of the contour vector is generated (S).
3). The contour vector data and the core line vector data are stored in the system memory 7. The host processor 9 separates / extracts elements such as character candidates, symbol candidates, and line segment candidates from these vector data (S4). A character dictionary, a symbol dictionary, and the like are prepared in the system memory 7, and the host processor 9 performs pattern recognition with reference to the dictionary as necessary for various separated elements (S5 to 7). Line type recognition is performed for line segment candidates. After that, the recognized pattern data is edited into a predetermined format as a recognition result (S8), and the recognition result is CAD.
Performs various output processing such as delivering to the system (S
9).

In the above-mentioned line type recognition, after tracing line segments and connecting line segment elements including discontinuous parts such as broken lines and chain lines,
Determine the line type. In this line segment tracking, as shown in FIG. 7, a reference line is sequentially selected (S1, 2), and tracking processing is performed in the starting point direction and the ending point direction of the reference line (S3 to).
6). In the tracking process, as shown in FIG. 8, first, an end point of the core vector (or thin line vector) on the tracking direction side is set as a reference point (S1), and a vector search area is set by this reference point to select a vector as a connection candidate. Search (S
2). Next, based on the direction and distance / angle of the vector,
A vector to be connected is determined from the connection candidate vectors (S3). If there is a vector that satisfies the connection condition (S
3: Yes), move to the relevant connection candidate vector (S
4), a series of processing is repeated. If there is no vector that satisfies the connection condition (S3: No), the tracking ends.

Thereafter, a line type discrimination process is performed on the traced line segment. In this line type discrimination, as shown in FIG. 9, a distribution of line segment lengths (vector lengths) and distances between the segments is taken (S1), and this distribution state is evaluated (S2, 3) and evaluated. The broken line and the chain line are distinguished from the result (S
4, 5), and further, the chain line is finely discriminated into one-dot chain line, two-dot chain line, etc. (S6).

[0006]

In the above-described conventional line type recognition, in the line segment tracking process, the tracking of the line segment is terminated at the point of time when tracking becomes impossible, but it is determined that tracking is not possible at the branch point. Has become. For this reason, good line segment tracking can be performed with drawings such as topographic maps with few intersections of line segments.
In equipment diagrams and machine diagrams with many intersections of line segments, there is a problem that the tracking section is shortened and the number of cut-out points of the tracking section is increased, and the line type recognition accuracy is also reduced. there were.

In the line segment tracing process, when the branch point is reached, if the appropriate one can be selected from the branching line segments and the tracing can be continued, the above problems can be solved. , It is difficult to identify the line segment to be traced. As an example, when the crossing angle is close to 90 ° as shown in FIG. 10A, a skeleton vector intersecting at one point is generated in the skeleton vector processing, so that it is relatively easy to continue tracking. Although conceivable, when the intersection angle is acute as shown in FIG. 10B, the core line vectors do not intersect at one point, and two branch points are generated. In this case, it is difficult to accurately track both of the two intersecting line segments.

In view of the above problems, it is an object of the present invention to improve the recognition rate of line type recognition by making it possible to continue the line segment tracking at a branch point in the line type recognition technology in a drawing input device or the like. .

[0009]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention uses a line segment element data obtained by separating and extracting an image from vector data approximated by a polygonal line as a processing target and tracing the vector. A method of performing seed determination, which is a method of tracing a vector by detecting a vector to be connected to an end point of a pending vector, in the case where two line segments intersect and the intersection of the two line segments. Categorize the vector connection relationship when the discontinuity of the line segment is compounded, and based on the categorized vector connection relationship, if the end point of the pending vector is a branch point and the end point of the vector to be connected is a branch point. It is designed to trace a line segment in some cases.

Further, as shown in FIG. 1, an apparatus for performing line type determination after tracking a vector with line segment element data obtained by separating and extracting an image from vector data subjected to polygonal line approximation, An apparatus for tracking a vector by detecting a vector to be connected to the end point of the pending vector is provided with the following elements.

(1) An end point branch determination means 11 for determining whether the end point of the pending vector is a non-branch point or a branch point.

(2) It is selected when the end point of the pending vector is a non-branch point, the non-branch end point is searched in a predetermined area with the end point as a reference, and the vector connected to this non-branch end point is connected. Non-branch-non-branch connection determination means 12 for determining the propriety.

(3) The non-branch-non-branch connection determination means 12 is selected when a vector that can be connected is not detected, and a branch end point is searched within a predetermined area based on the end point of the pending vector, and this branch end point is searched. Non-branch-branch connection determination means 13 for determining whether or not to connect a plurality of vectors connected to.

(4) Direct connection vector connection determination means 14 which is selected when the end point of the pending vector is a branch point and determines whether or not the plurality of vectors connected to this branch point can be connected.

(5) The direct connection segment connection determination means 14 selects a vector that is connectable and does not detect a vector that is connected to the pending vector via the connection error vector, and determines whether the searched vector can be connected. Indirect connection vector connection determination means 15 for determining.

(6) When the end point of the concern vector is a branch point, a non-branch end point is searched within a predetermined area based on the end point of the concern vector, and a plurality of vectors connected to the non-branch end point are searched. Branch to determine whether connection is possible-
Non-branch connection determination means 16.

[0017]

According to the present invention, even if the end point of the concern vector is a branch point or the searched other end point is a branch point, as long as the case assumed in advance is satisfied,
Set the connection candidates appropriately. That is, when the end point of the concern vector is a non-branching point, first, the non-branching-
Search for a connection target by non-branch connection and determine whether or not the connection is possible. At this time, if the connection target is not found,
Immediately without determining that tracing is impossible, a target to be connected by non-branch-branch connection is searched, and it is determined whether or not the plurality of vectors connected to the branch point can be connected. Also, even if the end point of the pending vector is a non-branch point, it is not immediately determined that the trace is impossible, but whether or not the vector is connected to the non-branch point is determined as a target. Furthermore, if the connection target is not found in this judgment, considering that the connection error vector may occur at the branch point in the vectorization process, search and judge the vector connected to the concern vector via the connection error vector. To do. In addition, a search / determination of a connection target by branch-non-branch connection is also performed.

[0018]

Embodiments of the present invention will be described below. The drawing automatic input device according to this embodiment is characterized by a line segment recognition process of line segment candidates, and particularly a line segment tracking process. This processing function can be realized by software. In this case,
The hardware configuration may be an existing configuration as shown in FIG. 5, for example.

The main point of the line segment tracing process according to the present embodiment is that the vector connection relation is patterned for the discontinuous portion of the line segment or the intersection portion of the line segments, and a connected vector selection algorithm corresponding to each pattern is added. To do. FIG. 2 shows assumed connection relation patterns and vector connection relations corresponding to the respective patterns. Pattern 1 is a case where a discontinuity exists in the pending line segment, and the vector connection relationship in this case is “non-branch point-non-branch point”. Pattern 2 is a case in which another line segment intersects a pending line segment having a discontinuity, and another line segment overlaps the discontinuity end point (tracking destination side), and the vector connection relationship in this case is It becomes "non-branch point-branch point". Pattern 3 is a case where another line segment intersects a continuous suspension line segment and the intersection portion is connected at a single end point, or another line segment which has a discontinuous portion intersects with the continuous suspension line segment. However, this is the case where the discontinuity end points of other line segments overlap the pending line segment, and in these cases, one of the vectors that directly branches from the reference vector becomes the connected vector. In pattern 4, another line segment intersects the pending line segment,
In addition, this is a case where a short connection error line segment is generated in the vectorization process because it intersects at an acute angle. In this case, the reference vector and the connection vector are indirectly connected via the connection error vector. Pattern 5 is a case where a discontinuity exists in the pending line segment, and another line segment overlaps the discontinuity end point (tracking source side). In this case, the vector connection relationship is "branch point-non-branch It becomes "point".

In order to deal with each of the above patterns, line segment tracing processing is performed according to the procedure shown in FIGS. In this process, first, the end point of the reference vector on the tracking destination side is set as a reference point (S1), and it is confirmed whether the reference point is a non-branch point or a branch point (S2). If the reference point is a non-branch point, the pattern 1 is determined (S3 to 6).
That is, a non-branch point is searched for in a predetermined area with the reference point as the base point (S3). If a non-branch point is found (S4:
Yes), targeting the vector connected to the non-branching point, it is determined whether or not the connection is possible based on the distance / angle between the end points and the angle with the reference vector (S5). As a result, if a vector that can be connected is found (S6: Yes),
The vector is confirmed as a connected vector, the connected vector is designated as the next reference vector, and the tracking process is continued (S7).

If a non-branch point is not detected in the judgment of pattern 1 (S4: No) or a connectable vector is not found (S6: No).
Determines pattern 2 (S8-11). That is, the branch point is searched in the same procedure as the above non-branch point search (S8). If a branch point is found (S9: Yes), it is determined whether or not each vector connected to the branch point can be connected (S10). As a result, if a connectable vector is found (S11: Yes), it is determined as a connected vector (S7). If no branch point is detected (S9: N
o) Or, if a connectable vector is not found even if a branch point is found (S11: No), it is determined that tracking is impossible (S12).

On the other hand, if the reference point is a branch point (S2:
If No, the pattern 3 is determined (S13, 14).
That is, first, it is determined whether or not to connect each branch vector connected to the reference point as a target (S13). As a result, if a vector that can be connected is found (S14: Yes), the vector is fixed as a connected vector (S7).

If no connectable vector is found in the judgment of pattern 3 (S14: No), the judgment of pattern 4 is carried out (S15-18). That is, the connection error vector (see FIG.
0 (see (b)) exists (S1)
5). This confirmation can be performed based on the fact that the vector length is short and both end points are branch points. When the connection error vector candidate is detected (S16: Yes), it is determined whether or not the branching vector connected to the tracking destination side of the connection error vector candidate can be connected (S17). As a result, when a vector that can be connected is detected (S18:
yes), the vector is fixed as a connected vector (S
7).

If the connection error vector candidate is not found (S16: No) or the connectable vector is not found (S18: No), the pattern 5 is judged (S19 to S22). That is, a non-branch point is searched for by the same procedure as S3 (S19). As a result,
If the non-branch point is found (S20: Yes), it is determined whether or not the vector connected to the non-branch point can be connected (S21),
If it can be connected, the connection vector is determined (S7). If the non-branch point is not found (S20: No) or if the vector is not concatenable even if found (S2).
2: No) makes tracking impossible (S12).

[0025]

As described above, according to the present invention,
When a line segment intersects, or when a line segment discontinuity part is compounded at the intersection of line segments, the vector connection relationship is categorized, and connection candidates are identified based on this. It is possible to continue tracking even for the line segment that
Good tracking is possible over the entire area without fragmentation at the intersection. Therefore, the accuracy of the line type discrimination performed using the tracking result is also improved.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of the present invention.

FIG. 2 is an explanatory diagram showing an assumed connection relationship pattern and a vector connection relationship corresponding to each pattern.

FIG. 3 is a flowchart showing line segment tracking processing according to an embodiment of the present invention.

FIG. 4 is a flowchart showing a line segment tracking process according to an embodiment of the present invention.

FIG. 5 is a block diagram showing a hardware configuration of the drawing automatic input device.

FIG. 6 is a flowchart showing an outline of operation of the drawing automatic input device.

FIG. 7 is a flowchart showing an outline of a line segment tracking procedure.

FIG. 8 is a flowchart showing conventional line segment tracking processing.

FIG. 9 is a flowchart showing line type discrimination processing.

FIG. 10 is an explanatory diagram showing how a connection error vector is generated.

[Explanation of symbols]

 11 ... End point branch determination means 12 ... Non-branch-non-branch connection determination means 13 ... Non-branch-branch connection determination means 14 ... Direct connection vector connection determination means 15 ... Indirect connection vector connection determination means 16 ... Branch-non-branch connection determination means

Claims (5)

[Claims] 1. A method for performing line type determination after tracing a vector with line segment element data obtained by separating and extracting an image from vector data approximated by a polygonal line, the method comprising: In a method of tracing a vector by detecting a vector to be connected, a vector connection relationship in the case where two line segments intersect and in the case where the discontinuity of the line segment is compounded at the intersection of the two line segments Line type recognition, characterized by categorizing a line and tracing line segments when the end points of the pending vector are branch points and when the end points of the vectors to be connected are branch points. Method. 2. An apparatus for performing line type determination after tracing a vector with line segment element data obtained by separating and extracting an image from vector data approximated by a polygonal line, which is for an end point of a pending vector. In an apparatus for tracking a vector by detecting a vector to be connected, an endpoint branch determination means for determining whether the endpoint of the pending vector is a non-branch point or a branch point, and the endpoint is a non-branch point Non-branch-non-branch connection determining means for determining a non-branching end point in a predetermined area based on the end point and determining whether or not the vector connected to the non-branch end point can be connected; This is selected when a vector that can be connected is not detected by the branch connection determination means, a branch end point is searched within a predetermined area with the end point as a reference, and a branching connection point is connected. A line type recognition device comprising: non-branch-branch connection determination means for determining whether or not to connect a number vector. 3. An apparatus for performing line type determination after tracing a vector with a line segment element data obtained by separating and extracting an image from vector data approximated by a polygonal line, which is for an end point of a pending vector. In an apparatus for tracking a vector by detecting a vector to be connected, an end point branch determination means for determining whether the end point of the pending vector is a non-branch point or a branch point, and when the end point is a branch point A line type recognition device, comprising: a direct connection vector connection determination means for determining whether or not to connect a plurality of vectors selected and connected to the branch point. 4. The line type recognition device according to claim 4, wherein when the directly connectable line segment connection determining unit does not detect a vector that can be connected, it is selected and a vector that connects to the pending vector is searched for via the connection error vector. Then, the line type recognition device is provided with an indirect connection vector connection determination means for determining whether or not the searched vector can be connected. 5. An apparatus for performing line type determination after tracing a vector with line segment element data obtained by separating and extracting an image from vector data approximated by a polygonal line, and for determining an end point of a pending vector. In an apparatus for tracking a vector by detecting a vector to be connected, an end point branch determination means for determining whether the end point of the pending vector is a non-branch point or a branch point, and when the end point is a branch point A branch-non-branch connection determining means for searching for a non-branching end point within a predetermined area based on the end point of the pending vector and determining whether or not to connect the plurality of vectors connected to the non-branch end point. A line type recognition device characterized in that