JPH07120367B2 - Symbol recognition method for drawing reader - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Outline] A symbol recognition method of a drawing reading apparatus for extracting and recognizing symbols in a read drawing forming a loop, and improving a recognition rate of symbols drawn by a template or a plotter. In addition, for the purpose of eliminating the need for a symbol dictionary for each type of drawing, the inside contour lines of the drawing image are vectorized to create loops, the loops are grouped for each loop that can be connected, and then the shape of each loop in the group is looped. The determination is made by matching with the shape dictionary pattern, and finally the symbol shape is determined by matching with the symbol dictionary pattern indicating the combination of the loop shape patterns.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a symbol recognition method of a drawing reading device for extracting and recognizing a symbol in a read drawing forming a loop, and in particular, extracting a symbol neatly drawn by a template, plotter or the like. TECHNICAL FIELD The present invention relates to a symbol recognition method of a drawing reading device for recognition.

In recent years, automatic input systems that input read drawing data into CAD systems for freehand drawings that comply with input drawing conventions in the system diagrams of petroleum refining plant equipment have come to the level of practical use due to research and development. ing. However, when this automatic input system is applied to a clean drawing drawn with a template or plotter, the recognition rate is almost the same as in the freehand case, although the distortion of the symbols in the drawing is small. Improvement of recognition rate is desired.

[Prior Art] A conventional symbol recognition method is intended for a freehand drawing according to an input drawing convention, and converts image data of a drawing symbol into thinned vector data by thinning processing, and loops from thinned vector data. , Symbol points are extracted based on characteristic conditions such as bending points and fills, and then symbol recognition is performed by pattern matching at the image data level with the symbol dictionary (Nikkei Electronics 418, pp80-82 (1987) "Handwriting Drawing Automatic "Reading system", edited by the Institute of Electronics, Information and Communication Engineers, "Pattern Recognition," Corona Publishing Co., Ltd. (1988) pp196-201).

[Problems to be Solved by the Invention] However, in the conventional symbol recognition method, the loop extraction is performed based on the thinned vector data generated from the image data, and the symbols drawn by the template and the plotter are extracted. Even if the distortion is small, there is a problem in that the shape of the loop forming the symbol cannot be determined, an error occurs in symbol extraction, and the recognition rate cannot be improved.

FIG. 11 shows an example of a symbol extraction error in the conventional method. In the case of FIG. 11A, since the line of the part A is short, the symbol extraction including the part other than the original symbol is performed. FIG. 2B shows a case where an error occurs because each of the loops formed by the circles included in the rectangle at four positions is regarded as an independent symbol.

On the other hand, the drawing symbols are not only basic drawings such as circles, arcs, triangles, quadrangles, and hexagons, but also consist of combinations of these basic figures. For example, the type of input drawings such as oil refinery plant system diagram to electric circuit diagram There is also a problem that a symbol dictionary must be prepared for each type of drawing, because the symbols used are completely different when changing.

The present invention has been made in view of such conventional problems, and improves a recognition rate of symbols accurately drawn by a template, a plotter, or the like, and a drawing reading apparatus that does not require a symbol dictionary for each drawing. It is intended to provide a symbol recognition method.

[Means for Solving the Problems] FIG. 1 is a diagram illustrating the principle of the present invention.

First, the present invention is directed to a symbol recognition method of a drawing reading device for extracting and recognizing symbols in a read drawing forming a loop drawn by a template, plotter, or the like.

According to the present invention regarding such a symbol recognition method, a first step 10 for vectorizing an inner contour line of a drawing image to create a loop; and a group for each loop to which the loop created in the first step 10 can be connected. A second step 12 for converting the loop shape of each group obtained in the second step 12 by matching with a loop shape dictionary pattern; and a third step 14; within the group determined in the third step 14. And a fourth step 16 for determining a symbol shape by matching each combination of loop shapes with a symbol shape dictionary pattern.

Here, in the first step 10, when the loop is created by vectorizing the inner contour line of the drawing image, it is determined whether the created loop is included in the allowable range determined by the predetermined rectangular size, and the allowable range is determined. A vectorized loop is valid only if it is contained within.

Also, when grouping created loops in the second step 12,
It is determined whether or not a plurality of loops grouped within an allowable range determined by a predetermined rectangular size are included, and only when included within the allowable range, the loops are grouped into the same group.

Further, the determination of each loop shape in the group in the third step 14 is at least a loop shape classified into a circle, a semicircle, a 1/4 circle, a 3/4 circle, a trapezoid, a square, a rectangle, a hexagon, a triangle and a right triangle. Determine using a dictionary pattern.

Furthermore, when the specific symbol shape including the combination of the plurality of loop shapes is determined in the fourth step 16, the connection shapes of the plurality of loop shapes are additionally confirmed.

[Operation] With the symbol recognition method of the drawing reading device according to the present invention having such a configuration, attention is paid to the fact that the inside contour line is less distorted in a symbol in a drawing drawn by a template, plotter, or the like. It is possible to vectorize the inner contour line to determine the loop shape, perform symbol extraction and recognition based on the result, and improve the symbol recognition rate of the drawing by the template or plotter.

In addition, the loop shape determined from the inner contour line is grouped for each loop that can be connected, the loop shape is determined by matching with the loop shape dictionary pattern that stores the basic loop shape, and finally the symbol shape is determined by combining the loop shapes. Since the symbol shape is recognized by the combination and matching of the specified symbol structure dictionary pattern and the loop shape forming the group, the loop shape dictionary pattern consisting of basic shapes such as circles, arcs, triangles, squares and hexagons is Can be used in common even if the type of changes, just change the symbol dictionary pattern that determines the combination of basic shapes,
The symbols can be recognized according to the type of the drawing, and the symbol dictionary for each drawing can be substantially eliminated.

[Embodiment] FIG. 2 is a block diagram of an embodiment of a drawing reading apparatus in which the symbol recognition method of the present invention is implemented.

In FIG. 2, reference numeral 18 denotes an image input unit, which optically reads a drawing, for example, a petroleum refining plant system diagram, by OCR or the like and converts it into image data. According to the present invention, when a drawing drawn by a template or a plotter is read from the image input unit 18, the symbols in the read drawing are effectively recognized. The drawing image data read by the image input unit 18 is given to the contour vectorization unit 20, and the contour of the image is vector-approximated by a circle and a line to create a loop. In the conventional method as the contour vectorization unit 20, a thinning vector is generated by thinning processing to create a loop, but in the symbol recognition method of the present invention, the inner contour line of the symbol image is generated. A vector is approximated with a circle and a line to create a loop. That is, as shown in FIG. 4, when a circle input image is used as a symbol drawn on a template or plotter, for example, the circle symbol 44 drawn on the template or plotter has a line with a certain thickness. It is generated as image data. A symbol with such a line thickness
On the other hand, in the conventional method, the thinning process is performed as shown in (4), and the thinned image data is left between the outer contour line and the inner contour line. Generate a thinned vector. In this thinning processing, the thinned image 46 does not necessarily become a perfect circle, but becomes data having fluctuation in the range of line thickness as shown in the figure. For this reason, even a circle drawn neatly as shown by the symbol 44 by the template or plotter becomes the thinned image data 46 which is distorted by the thinning process, which causes the symbol recognition to fail.

Therefore, in the present invention, as shown in, paying attention to the fact that the inner contour line 48 of the symbol drawn by the template or plotter has almost no distortion, the inner contour line 48 is taken out as the image data 50, and A loop is created by vector-approximating the outline image data 50 with a circle and a line.

Here, a loop is a portion of a line figure that can start from a certain point on the line figure and return to the original starting point without going through the same point twice, and inside this, another connected closed loop Defined as nonexistent.

Referring again to FIG. 2, the loop obtained by vectorization of the inner contour line of the symbol in the contour vectorization unit 20 is given to the symbol extraction unit 22. Symbol extractor
22 includes a contour loop grouping unit 24 and a group loop shape determining unit 26. Work tables 1, 2, and 3 are provided to execute the loop processing in the contour loop grouping unit 24. In addition, the loop shape dictionary table 34 is used to determine the loop shape in the group loop shape determination unit 26.

That is, the contour loop grouping unit 24 includes the contour vectorization unit 20.
Group the loops created in the above for each loop that can be connected. Further, the group loop shape determination unit 26 determines the shape of each loop forming the group obtained by the contour loop grouping unit 24 by matching with the registered pattern of the loop shape dictionary table 34, and determines the determined loop shape pattern number. A symbol configuration loop shape table 36 stored for each group is created. The symbol recognition unit 38 retrieves the loop shape pattern number forming the group for each group from the symbol structure loop shape table 36, and matches it with the combination of the loop shape patterns forming the symbol shape stored in the symbol structure dictionary table 40 in advance. Is performed to determine the symbol shape and output as the recognition result 42.

FIG. 3 is an example processing flow chart showing an example of the symbol recognition method of the present invention implemented in the configuration diagram of the example of FIG.

The processing flow of FIG. 3 is composed of steps S1 to S12, but the correspondence with the first to fourth steps shown in FIG. 1 is that steps S1 to S4 are the first step and steps S5 to S8 are the same. Second
Steps S9 and S10 are the third step, and steps S11 and S12 are the fourth step. Hereinafter, the first process to the fourth process in FIG.
Each of the processes will be described in detail.

[First Step] This first step is composed of steps S1 to S4, extracts symbols in the read drawing forming a loop drawn by a template or plotter, and vectorizes the inner contour line of the drawing image to create a loop. To create.

First, in step S1 (hereinafter “step” is omitted), the inner contour line of the drawing image data is vectorized by a circle, a circular arc, and a line to create a loop. The loop creation by vectorization of the inner contour line is as shown in FIG.

Then, the process proceeds to S2, and it is determined whether or not the checking of all loops is completed. If the checking of all loops is not completed, the process proceeds to S3, and it is determined whether or not the loop size of the loop created in S1 is within the allowable range. That is, as shown in FIG. 5, a vertical H and a horizontal V that include loops forming a symbol depending on the type of drawing.
Since the minimum rectangle size having the dimension of is determined in advance, it is determined whether the created loop is included within the allowable range determined by the minimum rectangle size that determines this loop size. Specifically, for example, the projection distance of the triangle forming the loop on the x-axis may be compared with the horizontal upper limit size V, and the y-axis projection distance of the triangle may be compared with the vertical upper limit size H.

Referring again to FIG. 3, if the loop size is within the allowable range in S3, the process proceeds to S4, and the created loop is stored in the work table 1 in FIG. On the other hand, if the size of the loop created in S3 is out of the allowable range, it is not regarded as a loop forming a symbol and the loop is not registered in the work table 1.

When the checking of all loops obtained from the read drawing is completed in S2, the process proceeds to the second step consisting of S5 to S8.

[Second Process] In the second process, the loops stored in the work table 1 created in the first process are targeted, and a process of grouping each connectable loop is performed.

First, in S5, the adjacency relation is examined for the loops in the work table 1, and the loops that can be connected are grouped and stored in the work table 2.

Then, the process proceeds to S6, and after the checked process of the work table 2 is performed, the process proceeds to S7, and it is determined whether the grouped loop size stored in the work table 2 is within the allowable range. The determination in S7 as to whether or not it is within the allowable range of the grouped loop size is performed as shown in FIG.

FIG. 6 shows one of the symbols used in the oil refining plant equipment system diagram in (a) as an input shape.
The minimum rectangle including each loop used in the determination of whether the loop size is within the allowable range in S3 in the first step in the figure is as shown in (b). Since the loops included in the four minimum rectangles shown in FIG. 6B have a connection relationship, they are grouped and stored in the work table 2. Therefore, in S7 of FIG. 3, as shown in FIG. 6C, the loop size grouped within the allowable range determined by the minimum rectangular size including each loop of FIG. 6B is included. Is determined.

Referring again to FIG. 3, if the loop size grouped in S7 is within the allowable range, the process proceeds to S8 and the work table 2
Group is stored in the work table 3.

When the check on whether or not the loop size grouped by S6 to S8 is included in the allowable range is completed for all of the work table 2, the process proceeds to the third step consisting of S9 and S10.

[Third Process] In the third process, for each of the groups determined in the second process, one or a plurality of loop shapes forming each group are determined by matching with the loop shape dictionary pattern.

That is, in S9, it is determined whether or not all the checks of the work table 3 are completed, and the process proceeds to S10. In S10, each loop shape forming the group is determined, and the symbol configuration loop shape table 36 is created based on the determination result.

A concrete example of symbols used in the oil refining plant system diagram is as follows.

Fig. 7 is an explanatory diagram of the symbols used in the petroleum refining plant system diagram. As shown in the figure, No. 1 to No. 12
Symbols with different loop configurations are used. For symbols consisting of No. 1 to No. 12 like this, refer to S10 in FIG.
The loop shape dictionary pattern 34 shown in FIG. 8 is registered in advance in the loop shape dictionary table 34 used to determine the loop shape.

In FIG. 8, the loop-shaped dictionary pattern is a pattern 100 as a circle, a pattern 110 as an upper half circle, a pattern 111 as a lower half circle, and a pattern 120, 1/4 consisting of 3/4 circles.
Circle pattern 121, Square pattern 200, Rectangular pattern 210, Hexagonal pattern 300, Upward trapezoidal pattern 310, Downward trapezoidal pattern 320, Rightward triangular pattern 400, Leftward facing Pattern 410 composed of triangles, a pattern 500 composed of right-angled triangles in the upper left corner, a pattern 500 composed of right-angled triangles in the lower left corner, a pattern 502 composed of right-angled triangles in the lower right corner, and a right-angled part It consists of a pattern 503 consisting of a right triangle in the upper right corner.

In the right-angled triangle patterns 500, 501, 502, 503, the bottom line when the right-angled portion is the apex may be a jagged line, a polygonal line, or an arc, as shown in the figure, other than a straight line.

With respect to the loop shape dictionary table 34 in which each pattern shown in FIG. 8 is registered, each loop shape registered in the work table 3 is read out for grouping and matching is performed. Finally, the symbol configuration loop shape table 36 is arranged.

When all the work table 3 checks have been completed in S9 of FIG. 3, the process proceeds to the fourth step of S11 and S12.

[Fourth Process] In the fourth process, the contents of the symbol configuration loop shape table 36, which is a combination of the loop shapes forming the group determined in the third step, specifically, pattern numbers indicating the loop shapes, The symbol shape is determined by reading out for each group and performing matching with the dictionary pattern of the symbol configuration dictionary table 40 prepared in advance.

That is, in S11, it is determined whether or not all checks of the symbol configuration loop shape table 36 have been completed, the process proceeds to S12, the combination of the pattern numbers of the loop shapes forming the first group is read from the symbol configuration loop shape table 36, and the symbol is read. Matches with the configuration dictionary table 40.

FIG. 9 is an explanatory diagram of the symbol configuration dictionary table 40,
12 kinds of symbol No. 1 to No. 12 shown in Fig. 7,
It stores the number of loop patterns forming the symbol shape of each symbol No., the pattern number of each loop pattern, and table information including additional confirmation items to be performed after symbol determination.

For example, symbol No. 1 is a circular symbol as shown in FIG. 7, and the number of patterns forming a loop is naturally one, and the pattern number of this loop shape is 100 as shown in FIG. Becomes

Looking at symbol No. 6, as shown in Fig. 7, symbol No. 6 is a symbol in which a circle is inscribed in a rectangle, and one line is added to the circle. The number of patterns is 6, and the types of 6 patterns are pattern 100 (circle), pattern 111 (lower half circle), and pattern in FIG.
501 and patterns 500-503 (like right triangles).

Further, in the symbol structure dictionary table of FIG. 9, additional confirmation items are provided. This additional confirmation is performed in principle when one symbol is generated by combining a plurality of loop shape patterns. That is, in FIG. 9, a circle is confirmed for symbols No. 4 and No. 6, a rectangle is confirmed for symbol No. 7, and a hexagon is confirmed for symbol No. 10. Check the connection for symbol No.12.

This additional confirmation will be specifically described with reference to FIG.

FIG. 10 (a) is a confirmation of a circle for symbols No. 4 and No. 6, and in symbol No. 4, the symbol is formed by the combination of the loop shape patterns 110 and 111 of FIG. , Check the circle to prevent the mistake of connecting up and down at the circumference without connecting at the radius. Regarding this point, since the semi-circular patterns 110 and 111 shown in FIG. 8 are combined with respect to the symbol No. 6, the circle indicated by the solid line is confirmed.

In the symbol No. 7 of FIG. 10 (b), two loop patterns 210 of FIG. 8 are overlapped, and a rectangle shown by a solid line is formed to prevent an error of overlapping them horizontally instead of vertically. Checking.

In the case of symbol No. 10 in FIG. 10 (c), the loop patterns 310 and 320 in FIG. 8 are piled up and down to form a hexagon. Check the solid line hexagons to prevent mistakes.

Further, the symbol No. 12 in FIG. 10 (d) has a symbol shape in which the loop patterns 400 and 410 formed by the triangles in FIG. 8 are connected to each other. Check that the triangle is located at.

Through the series of processes shown in the first process to the fourth process, it is possible to accurately recognize a symbol having a loop structure that is neatly drawn by a template, plotter or the like, and determine the symbol shape.

Although the above embodiment is intended for the drawing symbols of the petroleum refining plant system diagram, for example, a loop that constitutes a symbol even if the type of the drawing is changed and the symbol shape is different, such as an electric circuit diagram. As shown in FIG. 8, the shape is composed of basic figures such as circle, semicircle, 1/4 circle, 3/4 circle, triangle, trapezoid, square, and hexagon, as shown in FIG. The contents of the symbol configuration dictionary table must be a combination of the number of patterns and pattern numbers that match the drawing type, but the loop shape dictionary table is used commonly with basic figures stored regardless of the drawing type. Therefore, the symbol dictionary for each drawing can be substantially eliminated.

[Effects of the Invention] As described above, according to the present invention, it is possible to accurately extract a symbol in a read drawing that is neatly drawn by a plotter, a template, or the like, and improve the symbol recognition rate. It is possible to build a more practical drawing automatic input system by increasing the symbol recognition rate of the drawing drawn by the plotter or the template with respect to the drawing.

[Brief description of drawings]

FIG. 1 is a diagram for explaining the principle of the present invention; FIG. 2 is a block diagram of an embodiment of an apparatus to which the present invention is applied; FIG. 3 is a process flow chart of an embodiment of the present invention; Line vectorization explanatory diagram; FIG. 5 is an explanatory diagram of determination of the minimum rectangular size including the loop of the present invention; FIG. 6 is an explanatory diagram of adopted rectangle including the group of the present invention; FIG. 8 is an explanatory diagram of a symbol for a systematic diagram; FIG. 8 is an explanatory diagram of a loop shape dictionary pattern of the present invention; FIG. 9 is an explanatory diagram of a symbol configuration dictionary table of the present invention; and FIG. 10 is a dictionary matching of the present invention. Additional confirmation explanatory diagram; FIG. 11 is an explanatory diagram of errors in symbol extraction by the conventional method. In the figure, 18: image input unit 20: contour vectorization unit 22: symbol extraction unit 24: contour loop grouping unit 26: group loop shape determination unit 34: loop shape dictionary table 36: symbol configuration loop shape table 38: symbol recognition Part 40: Symbol structure dictionary table 42: Recognition result

Claims (5)

[Claims] 1. A symbol recognition method of a drawing reading device for extracting and recognizing symbols in a read drawing forming a loop drawn by a template, plotter or the like, wherein a loop is formed by vectorizing an inner contour line of a drawing image. A first step (10) for creating a loop; a second step (12) for grouping loops created in the first step into loops that can be connected; and a loop for each group obtained in the second step A third step (14) for determining the shape of the loop shape by matching with a loop shape dictionary pattern; and a symbol shape is determined by matching the combination of each loop shape in the group determined in the third step with the symbol configuration dictionary pattern. A symbol recognition method for a drawing reading device, comprising: a fourth step (16) of 2. The symbol recognition method for a drawing reading apparatus according to claim 1, wherein a predetermined rectangular size is used when the inner contour line of the drawing image is vectorized to form a loop in the first step (10). Symbol recognition of the drawing reading device characterized in that it is determined whether or not the created loop is included in the allowable range determined by, and the vectorized loop is validated only when the created loop is included in the allowable range. Method. 3. The symbol recognition method for a drawing reading device according to claim 1, wherein when the created loops are grouped in the second step (12), the groups are within an allowable range determined by a predetermined rectangular size. A method for recognizing symbols in a drawing reading device, comprising determining whether or not a loop to be converted is included, and grouping into a same group only when included in the allowable range. 4. The symbol recognition method for a drawing reading device according to claim 1, wherein the determination of each loop shape in the group in the third step (14) is at least a circle, a semicircle, a 1/4 circle, 3/4 yen, trapezoid,
A symbol recognition method for a drawing reading device, characterized by classifying into a square, a rectangle, a hexagon, a triangle, and a right triangle, and making a determination using a loop shape dictionary pattern. 5. The symbol recognition method for a drawing reading apparatus according to claim 1, wherein when a specific symbol shape including a combination of a plurality of loop shapes is determined in the fourth step (16), a plurality of symbol shapes are determined. A method for recognizing symbols in a drawing reading device characterized in that the connection shape of the loop shape is additionally confirmed.