JPH01312682A - Device for detecting inclination of character string or the like - Google Patents

Abstract

PURPOSE:To improve the precision of normalization by searching a projecting direction in which projecting length becomes shortest by inputting the projecting direction versus the projected length. CONSTITUTION:A projecting direction versus projecting length calculating device 2 generates the correspondence table of the projecting direction versus the projecting length by inputting the two-dimensional data of a character string, etc., read by a character string reader 1 and calculating and storing the project ing length of the character string for the projecting direction in a definite range. A minimum projecting length searching device 3 inputs the projecting direction versus the projecting length from the calculating device 2, and searches the projecting direction in which the projecting length becomes shortest. Thus, the title device is based on a principle that the projecting length in an inclining direction becomes shortest for almost all characters, and the degree of inclina tion of high precision can be obtained.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is applicable to, for example, vehicle plate number reading devices and all character reading devices that are effective by correcting the inclination of characters. The present invention relates to a tilt detection device.

[Conventional technology]

Conventionally, when character strings are recognized by image processing, a method is generally adopted in which each character is separated and cut out, and each character is matched to the most likely one by template matching. In this method, when reading characters, the height and width are usually set to standard values and then matched with the model pattern.

[Problem to be solved by the invention]

However, with the above method, if the plate, such as a vehicle license plate, is not installed vertically, the letters will be tilted diagonally, and if the template is used as is when viewed from the front, the possibility of misreading will increase. do. Furthermore, a similar problem occurs even when the characters themselves are tilted. In order to solve this problem, it is necessary to detect the inclination angle of the character from the character string itself and perform angle correction on the extracted character to improve the accuracy of normalization.

Therefore, the present invention provides a device for detecting the inclination of a character string, etc., which can detect the inclination angle of a character from the character string itself, perform all angle corrections on cut out characters, and improve the accuracy of normalization. The purpose is to

[Means to solve the problem]

In order to achieve the above object, the present invention includes a first means for internally reading or cutting out a character string as two-dimensional data from a character string, a figure similar thereto, or an image figure that meets these as parts; A second means for inputting the two-dimensional data read or cut out from a character string by means 1, calculating and storing the projected total length of the character string for a certain range of projection directions, and creating a correspondence table of projection directions versus projection lengths. And this second
and third means for inputting the projection direction versus projection length obtained from the means and searching for the projection direction in which the projection length is the shortest.

[Effect]

The present invention is based on the principle that for most characters, the projected length in the direction of inclination is the shortest.
Even if an exceptional character is included, it is not possible to determine the direction of projection that minimizes the sum of the projection lengths for all character examples. Therefore, it is possible to obtain a highly accurate inclination degree as a whole.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 (al) shows a schematic configuration of an embodiment of a device for detecting the inclination of a character string, etc. according to the present invention. This system reads a character string, a figure similar to the character string, or an image figure including the character string as a part as two-dimensional data, or extracts the character string.

The projection direction vs. projection length calculation device 2 includes, as shown in FIG. No, input the two-dimensional data of a character string read by a character string reading device! and calculate and store the projected total length of the character string with respect to a certain range of projection directions.
This is to create a correspondence table between projection direction and projection length.

The minimum projected length search device 3 inputs the projection direction versus projection length from the calculation device 2 and searches for the projection direction in which the projected length is the shortest.

The operation of the device for detecting the inclination of character strings, etc., configured as described above will be explained below, but before that, the principle of the device of the present invention will be explained with reference to FIG. 2.

Figure 2 (a), (bl both show that the degree of inclination of diagonally inclined characters can be expressed by a circumscribed parallelogram), Figure 2 shows changes in the projected length of characters. As an approximation of , we show how the projection length of a circumscribed parallelogram changes depending on the projection direction.
ψ. , and (b) is ψ. This is the case when ≦θ<T. Here ψ. is the slope of the parallelogram, θ is the projection angle, and the second
As is clear from the figure, ψ. It can be seen that the projected length is the minimum when and θ match, and that the projected length increases as it deviates from this.

Figure 3 shows θ and ψ for the actual character string 1.2.3. The shaded part in (a) is θ〈ψ.

When θ=ψ. When θ〉ψ. (b) shows the relationship between θ, ψ0 and the total projection length.

As is clear from this figure, θ=ψ. When , the projected length is at its minimum, and at this time the total projected length has a sharp peak (minimum value). The present invention applies such a principle.

FIG. 4 is for explaining the function of the projection calculation mechanism 23 shown in FIG. 1, in which the target image shown in FIG. Scanning ■・
...The shift amount calculated in advance in proportion to the scan ■ is converted into an integer, and the amount is transferred to the calculation buffer (not shown).
b) As shown in K, logical sums are accumulated corresponding to each address.

Figure 5 (al) shows an image assuming a projection angle θ, and the oblique shadow in the diagonal direction is obtained using the principle described above. This projection is the same as the logical sum in the vertical direction in Figure 5 (b). 5 (by shifting only the oblique shadow in the diagonal direction of al).This is determined as the logical sum in the vertical direction as shown in FIG. 5(b). Figure (b) shows the image output when this amount is corrected corresponding to each scan number 1 to 15.

Note that the vertical logical sum is calculated by scanning the image in FIG. It is the same as in FIG. 4 that the logical sum is inputted into the address and the logical sum is accumulated corresponding to each address.

In this way, when the logical sum operation is sequentially performed for the scan numbers ① to [phase], the projected image of the character string is stored as O/1/4' turns in the operation buffer (not shown). Therefore, if the total projection length calculation mechanism 24 counts 1'li1 elements among these results and stores them for each projection angle, the relationship shown at the bottom of FIG. 3 is formed in the projection length storage mechanism 25.

This result is searched by the minimum projection length search device 3 to find the minimum point ψ. It becomes possible to find. Since this method is used, as shown in the target image FiKG diagram (a
It is possible to use the intermediate coat type () or the cut-out type (b).

Furthermore, it is possible to handle both binary images and intermediate gradation images.

For black-and-white inverted images, as long as it is known whether the character structure is white or black, there is no big difference in handling either way.

Note that the present invention is not limited to the embodiments described above, and can be implemented as follows, for example. In other words, in terms of robustness, the same effect as that of Habo can be expected even if there is salt-and-pepper noise in which a portion of a character part is missing.

In addition, in the above-mentioned example, the projected length of the character was calculated using the minimum length, but
Conversely, even if you calculate the maximum projection length regarding the gap between characters,
It's exactly the same. In addition, as an alternative to the Hough transform, it is naturally possible to apply it to detecting the slope of a group of straight lines.

〔Effect of the invention〕

According to the present invention, the following effects can be obtained.

When reading characters, the vertical and horizontal widths are usually corrected to standard values and normalized (shift t of the scanning line is (N - 1) tarψ. Image obtained when stitched) and then matched with the model pattern. method is adopted.

In this case, if one character is tilted diagonally, not only will it be difficult to match it with the model/4' turn, but it will also have an adverse effect on the width calculation for normalization.

With the device of the present invention, the above-mentioned obstacles can be avoided by detecting the tilt angle and performing correction work.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of an embodiment of the inclination detection device for character strings, etc. according to the present invention, Figs. 2 and 3 are diagrams for explaining the principle of the embodiment, and Figs. 4 and 5 are diagrams for explaining the principle of the embodiment. FIG. 1 is a diagram for explaining the function of the projection calculation mechanism, and FIG. 6 is an explanatory diagram regarding character types to which the present invention is applied. 1...Character reading device (character string extraction device), 2...
- Projection direction vs. projection length calculation device, 3... Minimum projection length search device. Patent Attorney Ceremony for Applicant Patent Attorney Takeshi Suzue
Including Lj friend 2 figure and Mr. Karu's tape (b) Fig. 1'' (a) z a + h 1tan10- tanet (b) Fig. 2 (a) O The main exit is shifted and the shakuba is set on the right side of the bar.

Claims (1)

[Claims] A first means for internally reading or cutting out a character string as two-dimensional data from a character string, a figure similar thereto, or an image figure including the same as a part; Alternatively, the second method inputs the two-dimensional data from which the character string has been cut out, calculates and stores the projected total length of the character string for a certain range of projection directions, and creates a correspondence table of projection direction and projection length.
A device for detecting the inclination of character strings, etc., comprising: means for inputting the projection direction versus projection length obtained from the second means, and third means for searching for the projection direction in which the projection length is the shortest.