JPS60189084A - Character area extracting circuit - Google Patents

Abstract

PURPOSE:To extract a character area through a simple circuit by detecting the density gradient of an image, extracting a contour which limits the range of the character area on the basis of the projection value, and deciding on the character area according to the projection value of the limited range. CONSTITUTION:A picture from an input part 1 is converted into a 512X512 digital picture A differential arithmetic circuit ( I )2 detects the longitudinal edge through a differential filter and a differential arithmetic circuit (II)3 detects the lateral edge through a differential filter to obtain differential density values of the picture. Those outputs are inputted to projection circuits (longitudinal) 4 and (lateral) 5 respectively to project the number of picture elements having density values above a threshold value. Projection values of the projection circuits 4 and 5 are inputted to contour extracting circuit (longitudinal) 6 and (lateral) 7 to decide the contours. Both contours are inputted to projection circuits (longitudinal) 8 and (lateral) 9 together with the outputs of the differential arithmetic circuits, thereby detecting the longitudinal and lateral projections of a character part. Those projection values are inputted to character area line extracting circuits (longitudinal) 10 and (lateral) 11 to decide character area lines.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Technical Field of the Invention The present invention relates to an image recognition device, and more particularly to a character region extraction circuit that can extract character regions in an input image at high speed using a simple circuit. .

(2) Prior art and problems Conventionally, methods for extracting υ character areas from grayscale images include:
This method performs orthogonal transformation on the input image, extracts specific spectra corresponding to each, sets a threshold value for each spectrum, performs detection processing, and then extracts character area lines. This method has disadvantages in that the scale of the apparatus is large because it performs orthogonal transformation, and the processing speed is slow.

(3) Purpose of the Invention The purpose of the present invention is to extract the outline of a surface containing characters, limit the range containing the characters, and quickly extract the character area within that range using a simple circuit. It is an object of the present invention to provide a character area extraction circuit.

(4) Structure of the Invention In order to achieve the above object, the character area extraction circuit of the present invention has a contour in which the surface containing characters can be limited to a rectangular shape, and one side of the rectangle is approximately parallel to the scanning direction when entering the mountain. The image recognition device includes a density gradient detection circuit that detects the density gradient of the image, a projection circuit that projects the density gradient of the image obtained here, and a contour line that limits the range of the character area based on the projection value. The present invention is characterized by comprising a contour line extraction circuit for extracting contour lines, and a character area line extraction circuit for determining a character area based on a limited range of projection values.

(5) Embodiments of the Invention The principle of the present invention is as follows: When the input standby scanning direction is parallel to one side of the rectangular outline of a surface containing characters, the number of pixels having a density gradient greater than a certain threshold value is calculated in the scanning direction. It is clear that the contour line will be maximized if it is projected to . Therefore, if a projection is detected using another threshold in the range between the peaks of this maximum number of projections, the number of projections will be larger in the character area than between the characters.If this is done in both orthogonal directions, the character area will be detected. can be easily determined.

FIG. M1 is a configuration explanatory diagram of an embodiment of the present invention.

In the figure, the image of input unit 1 is 512x512 (
8-pit) digital image. The differential calculation circuit (■) 2 uses a differential filter having the shape shown in FIG. 2 (cc) to detect edges in the vertical direction and obtain the density differential of the image. The differential calculation circuit (n) 3 uses a differential filter having the shape shown in FIG. 2(b) to detect edges in the lateral direction and obtain density differentials of the image. These differential calculation circuits (1) 2,
(n) The outputs of 3 are respectively projected by the projection circuit (vertical) 4. (beside)
5, and the number of pixels having density differential values greater than or equal to a predetermined threshold in a predetermined range is projected in a predetermined direction.

Figures 6 (α) to (1) show this state, and the projection of the vertical edge to the character θ in the outline @ of the screen ■ in Figure 6 (,z) is shown in Figure 6 (b). ), (c) show the projection of edges in the horizontal direction (m), and (e) show the projection values of the entire screen. (c) and (d) respectively show the projection values within the contour line @.

The projection values shown in (b) and (d) in the same figure from the projection circuits 4 and 5 are transmitted to the contour extraction circuit (vertical) 6. (Horizontal) 7 and the contour line (vertical and horizontal) is determined.

Projection circuit (vertical)8. (Horizontal) 9 is inputted together with the outputs of the differential calculation circuit (1) 2, (l [J .

As a result, the projection values shown in FIGS. 3(c) and 3(e) are obtained. These projection values are processed by character area line extraction circuit (vertical) 10.
(Horizontal) 11, character area lines (vertical and horizontal) are determined, and a rectangular character area is obtained.

By performing detailed scanning of this character area, character recognition can be easily performed.

(6) As described in detail, according to the present invention, the range containing the υ character is limited by extracting the rectangular outline of the surface containing the character part, and within that range, the character Areas can be extracted quickly using a simple circuit.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of the configuration of an embodiment of the present invention, Fig. 2 (b),
(b) is an explanatory diagram of the differential filter of the main part of the present invention, and FIGS. 3(α) to (e) are explanatory diagrams of the operation of the main part of the present invention. is a differential calculation circuit, 4, 5, 8゜9
1 shows a projection circuit, 6 and 7 a contour line extraction circuit, and 10.11 a character area line extraction circuit. Patent applicant Fujitsu Ltd. sub-agent Patent attorney 1) Yoshishige Saka Figure 1 Figure 2 (a) (b) Figure 3 Horizontal position number

Claims (1)

[Claims] In an image recognition device in which a surface including characters has an outline that can be limited to a rectangle, and one side of the rectangle is approximately parallel to the scanning direction at the time of entering the mountain, a density gradient detection circuit that detects a density gradient of an image, and a density gradient detection circuit that detects a density gradient of an image; a projection circuit for projecting the density gradient of an image to be imaged; a contour extraction circuit for extracting a contour line for limiting the range of a character area based on projection values; and a contour extraction circuit for determining a character area based on the limited range of projection values. A character area extraction circuit comprising a character area line extraction circuit.