JP2655598B2 - Line segment extraction method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recognition device for optically reading characters and figures, and more particularly to a character reading device for reading handwritten characters using a line segment extraction method.

[Conventional technology]

In the conventional line segment extraction method, a direction image is created, and a pattern is uniformly blurred with respect to this image if necessary.
Alternatively, blur conversion is performed on a rectangle to extract a specific line segment.

Examples of blur conversion include “Theory of Character Recognition by Matching Method” (Yasuzo Iijima, IEICE Vol.56 No.5 pp
668-677 (1973)), as an example of directional image creation, “A Method for Extracting Directional Segments of Character Patterns without Thinning” (Babaguchi et al., IEICE Transactions Vol. J65-D)
No. 7 pp874-881 (1972)).

In the conventional line segment extraction method, a direction code image in which a direction code indicating the line segment direction is added to each pixel of the line segment portion of the input image is created, and the line segment is directly extracted, or Is subjected to image conversion by blurring uniformly or rectangularly, and line segments are extracted from the converted image.

In FIG. 7, the horizontal direction is quantized into four directions, "1", the direction at 45 ° to the horizontal direction is "3", the direction at 90 ° is "5", and the direction at 135 ° is "7". FIG. 8 shows an example in which the input image is replaced by the direction codes 1, 3, 5, and 7. FIG. 8 shows a direction image having only the horizontal component ("#" portion in the figure), and FIG. 9 shows the pattern shown in FIG. Shows an image after conversion is performed by uniformly blurring into a rectangular shape.

[Problems to be solved by the invention]

In many cases, handwritten characters or drawings are not always written in the correct direction when written in a specific direction. For example, a horizontal line written in a character often slightly rises to the right or is curved.
FIG. 7 shows an example of a pattern using such a character direction code.

In such a case, if a direction image is created for each value of the direction code, a horizontal line segment written upward to the right is extracted as an oblique line segment. Furthermore, it is extremely difficult to directly extract a line segment from a direction image, and complicated processing is required. When uniformly blurring or blurring in a rectangular shape, a plurality of adjacent parallel lines are connected, and the line segment is correctly extracted. Can not.

[Means for solving the problem]

In order to solve the above-mentioned problem, a line segment extraction method according to the present invention provides a device for optically reading characters, figures, and the like, wherein a first direction code indicating a direction of each line segment to be extracted from an input image and the first direction code. Means for giving a direction code of a quantization level consisting of a second direction code indicating the middle direction of an adjacent line segment of the direction code to each pixel of the input image to create a direction code image; In the code image, the pixel to which the first direction code is assigned is left as it is, and the pixel to which the second direction code is assigned is the first pixel indicating the direction closest to the direction indicated by the direction code. It is provided with means for converting into codes to create a directional image, and means for extracting line segments based on the created directional image.

[Action]

The assignment of the direction code based on the quantization level is performed by giving the input image more directions than the direction of the line segment necessary for extraction. As an example, when extracting line segments in four directions, direction codes in eight directions are assigned. When a direction image is created based on this, if the direction of the extracted line segment and the direction code match, this is used as it is, and the direction code that does not match the direction code of the extracted line segment is close to that code. A direction image is created assuming that the line segment is in both directions. The partial blur conversion performed only in a predetermined direction facilitates line segment extraction by preparing different masks according to the application and the direction of the line segment to be extracted and performing a blur conversion on the directional image. As an example, partial blur conversion of horizontal lines of a character will be described. The horizontal line of a character is generally written from left to right. From each pixel of the direction image of the horizontal line segment, the pixels continuously connected in any one of the eight directions are regarded as one line segment, and for the above-mentioned reason, the direction image is formed such that the end of one line segment becomes a rectangle. Is partially blurred. Extracting a line segment from the directional image to which the partial blur conversion has been applied can be easily performed by applying the conventional technology.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a flow chart showing the processing of an embodiment of the line segment extraction method of the present invention, FIG. 2 is a diagram of a direction code pattern, FIG. 3 is a diagram showing an example of a direction code image, and FIG. FIG. 5 is a diagram showing an example of a direction image of the direction, FIG. 5 is a diagram obtained by performing blur conversion on FIG. 4, and FIGS. 6 (a) and (b) are masks including evaluation pixels 7, 8 and mask positions 9 to 12. FIG.

In the present embodiment, a direction image in four directions (first direction codes 1, 3, 5, 7) is created. As shown in FIG. Second direction codes 2,4,6,8 are provided in intermediate directions of the respective directions 7, 7, and 1, and the direction codes 1,2, ..., 8
Is given.

Next, the processing of the line segment extraction method of this embodiment will be described with reference to the flowchart of FIG.

First, the line segments in the four directions to be extracted are represented by the direction codes 1 in the eight directions.
The pixels of the input image are replaced with 2, 8 to create a direction code image (process 1). Next, the second direction code in the intermediate direction is converted into first and second direction codes 1, 3, 5, and 7 before and after it (process 2), and four direction images are created for each first direction code (process 2). 3). Next, a partial blur return process is performed on each directional image to emphasize the direction of the line segment to be extracted (process 4).
The pattern of the direction image subjected to the partial blur conversion is projected in the direction of the extracted line segment (process 5), and the line segment is extracted by counting the maximum and minimum of the projected pattern (process 6).

Next, horizontal line segment extraction will be described with a specific example.

In process 1, direction codes 1, 2,
.., 8 are created. Processing 2
, The horizontal direction image (direction code 1) in processing 3 (the direction code 1 in FIG. 3 is “#” and the others are “0”).
Is converted). Then, in process 4, the horizontal image (FIG. 4) is sequentially scanned in the horizontal direction from the upper left using the mask shown in FIG. When "#" appears, "#" is inserted at a position corresponding to the evaluation pixel 7 of the horizontal image being scanned, and "0" is inserted at other positions to create one partially blurred converted image. Is stored. Next, FIG. 6 (b)
Then, horizontal scanning is sequentially performed from the lower left using the mask described above, and the same processing as described above is performed to create another partially blurred converted image. When the two images thus obtained are superimposed, a partially blurred converted image shown in FIG. 5 is obtained. This fifth
By projecting in the horizontal direction from the partially blurred transformed image in the figure and counting the number of local maxima and minima, it can be seen that there are four horizontal line segments.

〔The invention's effect〕

As described above, the present invention provides an input image with a greater number of direction codes than the direction of the line segment to be extracted, and then converts the input image into the direction of the extracted line segment, thereby absorbing a larger fluctuation in the direction of the extracted line segment. On the other hand, by performing partial blur conversion, more stable line segment extraction can be easily performed for relatively messy characters and drawings, and the line segment extraction method is featured. There is an effect that the reading performance of the recognition device can be improved.

[Brief description of the drawings]

FIG. 1 is a flowchart of a process showing an embodiment of a line segment extraction method according to the present invention, FIG. 2 is a pattern diagram of a direction code, FIG. 3 is a diagram of a direction code image, and FIG. , FIG. 5 is a view after performing a partial blur conversion on FIG. 4, FIGS. 6 (a) and (b) are views of a mask, FIG. 7 is a conventional direction code image, and FIG. FIG. 9 shows the horizontal direction image, and FIG. 9 shows the image after the conventional blur conversion.

Claims (1)

(57) [Claims] An apparatus for optically reading characters, figures, and the like, comprising: a plurality of first direction codes indicating a plurality of predetermined directions of each line segment extracted from an input image; and adjacent lines of the first direction code. Means for giving a direction code of a quantization level consisting of a plurality of second direction codes indicating a plurality of directions in the middle of the minute to each pixel of the input image to create a direction code image; Of the pixels, the pixels to which the first direction code is assigned are left as they are, and the pixels to which the second direction code is assigned are converted to the first code indicating the direction closest to the direction indicated by the direction code. Means for generating a directional image by performing a partial blur conversion on the directional image in a predetermined direction using a mask having directivity to generate a blur conversion direction image; Means for extracting a line segment based on an image.