JPH08235307A - Character string detector - Google Patents

Abstract

PURPOSE: To stably detect a character string regardless of inclination of the character string at the time or detecting the position of the character string from an image pickup range before character read. CONSTITUTION: The character picture taken in by a check picture input circuit 1 is stored in a variable density picture memory 2. Windows A and B are set in preliminarily determined positions by a window mask circuit 3, and variable density values are projected in X and Y directions in respective windows by an X and Y projection data circuit 4 to detect average variable density value distributions fAy(), fAx(), fBy(), and fBx (). The correlation function between distributions fAx () and fBx() is obtained by an X-direction correlation function calculating circuit 5, and the extent of phase deviation is detected by a horizontal deviation detection circuit 6, and the extent of deviation in the vertical direction is detected by distributions fAy() and fBy(). In an inclination detection circuit 8, the position of the character string is calculated by the deviation in the horizontal direction, and the inclination of the character string is calculated by the character length and the deviation in the vertical direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a character string position detecting device, and more particularly, when a character is cut out in character recognition, if there is a tilt in the character string direction, the tilt is calculated to stably detect the character string position. The present invention relates to a character string detection device.

[0002]

2. Description of the Related Art In a conventional character string detecting device, for example,
The character string detection method as shown in "Introduction to Character Recognition (The Institute of Electrical Communication)" P60 is used.

FIG. 3 is an explanatory view for explaining this conventional character string position detecting method.

As shown in FIG. 3, the gradation value of a character is projected on an axis (Y-axis) perpendicular to the character string. At this time, the upper end and the lower end of the character can be determined according to the pattern height of the character from the projection waveform and the threshold value that crosses the waveform, and thus each character string can be detected.

[0005]

In this conventional character string detection method, since the character height width is detected and the character string position is determined by the threshold processing from the waveform of the projection of the gray value, the character image has an inclination. In this case, there is a problem that the pattern height width cannot be detected and the character string position cannot be determined only by changing the threshold value.

[0006]

A character string detection device of the present invention is an image input circuit for picking up a target character string to generate a digital character image, a grayscale image memory for storing the character image, and the grayscale image memory. A window mask circuit for cutting out a region designated as a region for cutting out both ends of the character string, an XY projection data calculation circuit for detecting an average gray value distribution waveform in the horizontal and vertical directions in the region, An X-direction correlation function calculation circuit and a Y-direction correlation function calculation circuit for calculating a correlation function between the gray value distribution waveforms, a horizontal shift detection circuit for detecting a shift in the horizontal and vertical directions from the peak value of the correlation function, and a vertical shift detection A circuit and a tilt detection circuit that calculates the tilt of the character string from the detected shift amount are provided.

[0007]

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

FIG. 1 is a block diagram of a character string detecting apparatus according to an embodiment of the present invention.

A character image a from the image input circuit 1 for picking up a target character is stored in the grayscale image memory 2 as a grayscale image b. Next, in the window mask circuit A3 and the window mask circuit B3 ′, the images of the right end and the left end regions of the character string are cut out from the grayscale image b to form regions Ac and Bc ′. The cutout position and the size of the region are determined in advance by the position accuracy of the character string in the entire character image and the accuracy of the direction of detection.

Next, for each of the detected areas, the horizontal average gray value distribution waveform and the vertical average gray value distribution waveform in the area are calculated as X and Y projection data calculation circuits A4 and XY for each area. The projection data calculation circuit B4 ′ finds the X projection data Ad, the Y projection data Ae, the X projection data Bd ′, and the Y projection data Be ′, respectively.

Next, in the X-direction correlation function calculation circuit 5, X
The correlation function between the projection data Ad and the X projection data Bd ′ is calculated to obtain the X direction correlation value f, and similarly in the Y direction correlation function calculation circuit 5 ′, the Y projection data e and the Y projection data B are calculated.
The correlation function with e ′ is calculated to obtain the Y-direction correlation value g.

In the horizontal shift detection circuit 6, the peak position of the function is obtained from the X-direction correlation value f, and the shift amount of the waveform for which the correlation is obtained is output as the horizontal shift amount h. Similarly, in the vertical shift detection circuit 7, the peak position of the function is obtained from the Y-direction correlation value g, and the shift amount of the waveform for which the correlation is obtained is output as the vertical shift amount i.

The inclination detecting circuit 8 calculates the horizontal position of the character string from the horizontal shift amount h, the positional relationship between the respective areas A and B, and the character string length, and calculates the character string length and the vertical shift amount i. The inclination of the character string is detected by comparison. Further, the character string position is determined from the horizontal position shift of the character string. An accurate character string position can be detected by correcting the rotation of the character image a based on the inclination amount of the character string obtained as described above.

Next, the processing steps of the embodiment shown in FIG. 1 will be described with reference to FIG.

As shown in FIG. 2, average gray value distribution waveforms fay (), fax (), f in each direction of each area A and area B are shown.
bx () is represented. Correlation function Csx of waveform in each direction
() And Csy () are calculated based on the following equations. Csx (t) = Σ ((fax (t + k) −fs) * (f
bx (k) -fi)) k = 0, N (N: data calculation length) fs = fax (t + k): k = 0, average value of N fi = fbx (k): average value of k = 0, N Csy (t) = Σ ((fay (t + k) −fs) * (f
by (k) -fi)) k = 0, N (N: data calculation length) fs = fay (t + k): k = 0, average value of N fi = fby (k): average value of k = 0, N By finding the maximum position of these functions with respect to t, the relative position of each waveform can be determined.

[0016]

As described above, the character string detecting device of the present invention is provided with character inclination detecting areas at both ends of a character string,
Since the inclination is detected by the position shift of the character image in each area, the inclination of the character string can be detected stably without setting the reference character image and regardless of the change in contrast such as lighting. It has the effect that

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a character string detection device of the present invention.

FIG. 2 is a diagram for explaining the operation of the embodiment shown in FIG. 1;

FIG. 3 is a diagram illustrating a conventional character string detection method.

[Explanation of symbols]

 1 Image Input Circuit 2 Gray Image Memory 3 3 ', Window Mask Circuit 4 4', X / Y Projection Data Calculation Circuit 5 5 ', X / Y Direction Correlation Function Calculation Circuit 6 Horizontal Deviation Detection Circuit 7 Vertical Deviation Detection Circuit 8 Tilt Detection circuit

Claims (1)

[Claims] 1. An image input circuit for picking up a target character string to generate a digital character image, a grayscale image memory for storing the character image, and a character string in the grayscale image memory designated to cut out both ends of the character string. A window mask circuit that cuts out a region, an X / Y projection data calculation circuit that detects a horizontal / vertical average gray value distribution waveform, and an X direction that calculates a correlation function between the average gray value distribution waveforms. A correlation function calculation circuit and a Y-direction correlation function calculation circuit, a horizontal shift detection circuit and a vertical shift detection circuit that detect horizontal and vertical shifts from the peak value of the correlation function, and a tilt of a character string based on the detected shift amount. An inclination detection circuit for calculating