JPH0520794B2 - - Google Patents

Description

[Detailed Description of the Invention] [Summary] In a symbol recognition method that determines which of a plurality of candidate symbols the symbol is by determining graphical features from image data of the symbol to be recognized, When the result of image recognition is a symmetrical symbol, on the assumption that the image itself should also have symmetry, the image data is symmetrically transformed and the recognition process is performed again to create the same symbol. This is the recognition result only when it is recognized, and if the second recognition result does not match, the result is rejected.

[Industrial application field]

The present invention relates to an automatic graphic input device, and more particularly to a symbol recognition method when the shape of the recognized symbol is symmetrical.

With the recent improvement in the processing power of computer systems, drawings such as design drawings and maps are read as binary image data, line segment elements, symbol elements, character elements, etc. are extracted, and the design drawings, etc. are created into a database. It has become popular to output hard copies using the data constructed as databases, and to automate designs using logical simulations.

In this case, it is essential that the symbol elements of the design drawings, maps, etc. targeted by the database be accurately recognized, and a symbol recognition method that reduces the rate of misrecognition is now required.

[Problems to be solved by conventional technology and invention]

FIG. 4 is a diagram explaining the conventional symbol recognition method, in which (a) shows the result of executing a series of recognition processes once and shows the case where the recognition result is output, and (b) shows the case where the recognition result is output after performing two recognition processes.
This shows the case where two recognition processing units are provided.

In method (a), the recognition processing unit 1 executes a series of recognition processes once, and collates the obtained recognition result (code information) with known symbol code information stored in the symbol table 2. In particular, when the image itself has symmetry, such as a symmetrical symbol, there is a problem in that the above-mentioned one-time recognition does not provide the desired recognition result.

In the method (b), two recognition processing units 1 are provided, and in each of them, the code information of the recognized result is collated by the comparison unit 3, and if a matching output is not obtained, the recognition result is rejected. Although accuracy is improved compared to method (a), there is a problem in that the symbol recognition device becomes complicated.

In view of the above-mentioned drawbacks of the conventional art, the present invention, when it is detected that a recognized symbol is symmetrical, converts the image of the recognition target into a symmetrical shape, performs recognition again, and obtains the same recognition result. The purpose of this invention is to provide a method for obtaining more reliable recognition results by determining the recognition results for the symbols when they are obtained.

[Means for solving problems]

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

In the present invention, drawings such as design drawings and maps are read as binary image data, the extracted symbol elements are subjected to first symbol recognition processing in the recognition processing section 1', and the recognition results are symmetrical. If it is not a symbol, it is the recognition result, and if it is a symmetrical symbol, the image data is symmetrically transformed in the symmetrical transformation section 4, and then the recognition processing section 1' performs symmetrical transformation on the image data.
When the recognition process is executed for the second time, if the recognition result matches the previous recognition result, that is taken as the recognition result, and if the recognition result does not match, it is determined that recognition is not possible.

[Effect]

That is, according to the present invention, in a symbol recognition method in which graphical features are determined from image data of a symbol to be recognized to determine which of a plurality of candidate symbols the symbol is, an image to be recognized is When the recognized result is a symmetrical symbol,
Based on the assumption that the image itself should have symmetry, the image data is symmetrically transformed, the recognition process is performed again, and only when the same symbol is recognized is the recognition result. If the recognition results do not match, the results are rejected, so the recognition rate of symmetrical symbols can be improved, and the recognition process for image data with a relatively large number of symmetrical symbols can be performed. , which has the effect of reducing misrecognition.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.
FIG. 2 is a diagram showing an example of a symmetrical symbol to which the present invention is applied, and FIG. 3 is a flowchart showing symbol recognition operation according to the present invention.
Note that the same reference numerals indicate the same objects throughout the figures.

Hereinafter, the symbol recognition method according to the present invention will be explained with reference to FIG. 1 while referring to FIGS. 2 and 3.

The symbol recognition process according to the present invention is as follows. After reading the drawing, removing noise, filling in holes, etc. through recognition preprocessing (not shown), graphical element separation processing separates graphical elements such as lines, symbols, and characters before execution.

Further, the recognition process itself does not need to be a specific method, and any method such as an existing pattern matching method or feature matching method may be used.

First, in the recognition processing unit 1', the recognition result 1a
is output, and whether or not this is a symmetrical symbol is determined by the symmetrical determining section 11a based on the code information. (Steps 10, 11, 1
(See 2) This determination is made by referring to a symbol table 2' in which whether or not each symbol is symmetrical is defined in advance.

If the symbol is not symmetrical, the above result 1a is taken as the recognition result. (Step 1
(See 9) If the recognized symbol code indicates a symmetrical form, the image data is subjected to symmetrical conversion in the next symmetrical conversion unit 4.

Here, the type of symmetrical symbol shown in Figure 2 is considered, and the symmetrical transformation is determined by performing mathematical operations (for example, coordinate transformation with respect to the X-axis/Y-axis, etc.). do. (Step 13
(See) The recognition processing unit 1' executes recognition processing again on the image obtained by performing the symmetry transformation. This recognition process has the same content as the first time. As a result, a recognition result 2a is obtained.

Recognition result 2a obtained in this second recognition process
and the previous recognition result 1a are compared in the comparison circuit C12a, and if a matching output is obtained, it is taken as the recognition result, but if no matching output is obtained, either result 1a or result 2a is Whether both are correct or both are incorrect, the recognition processing according to the present invention functions to make it impossible to determine. (See Steps 14, 15, 16, 17, and 18.) In this way, when the present invention reads a figure with many symmetrical symbols and performs symbol recognition, it is possible to detect symmetrical symbols through a series of recognition processes. The feature is that when the figure is symmetrically transformed and the same recognition process is performed, the recognition result (code information) obtained is the recognition result only when it is the same as the previous recognition result. .

〔Effect of the invention〕

As described above in detail, in the symbol recognition method of the present invention, graphical features are determined from the image data of the symbol to be recognized, and it is determined which of a plurality of candidate symbols the symbol is. In a recognition method, when the result of recognizing an image to be recognized is a symmetrical symbol, the image data is symmetrically transformed and re-recognized based on the assumption that the image itself should also have symmetry. The recognition result is determined only when the symbol is recognized as the same symbol, and if the second recognition result does not match, the result is rejected. Therefore, the recognition rate of the symmetric symbol is This has the effect of reducing recognition errors in recognition processing for image data containing relatively many symmetrical symbols.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a diagram showing an example of a symmetrical symbol to which the present invention is applied, and FIG. 3 is a symbol recognition operation according to the present invention. A diagram showing the flowchart, No. 4
The figure is a diagram explaining a conventional symbol recognition method. In the drawing, 1 and 1' are recognition processing units, 11a
12a is a comparison circuit C, 2, 2'
3 indicates a symbol table, 3 a comparison section, 4 a symmetry conversion section, and 10 to 19 each processing step.

Claims (1)

[Scope of Claims] 1. A symbol recognition method that determines which of a plurality of candidate symbols the symbol is by determining graphical features from image data of the symbol to be recognized, comprising: a recognition processing unit 1 If the recognition result is not a symmetrical symbol, it is used as the recognition result; if it is a symmetrical symbol, the image data is subjected to symmetrical transformation in the symmetrical transformation unit 4, and then A symbol characterized in that the recognition processing unit 1' executes a second recognition process, and if it matches the previous recognition result, it is taken as the recognition result, and if it does not match, it is determined that it is unrecognizable. Recognition method.