Character pattern line thickness regularizing device

• US 4,010,446 A
• Filed: 06/27/1974
• Issued: 03/01/1977
• Est. Priority Date: 07/02/1973
• Status: Expired due to Term

• Current Assignee: Kabushiki Kaisha Ricoh
• Original Assignee: Kabushiki Kaisha Ricoh
• Inventors: Kawa, Ryuichi
• Primary Examiner(s): Boudreau, Leo H.
• Application Number:
  US05/483,740
• Time in Patent Office: 978 Days
• Field of Search: 340/146.3 H, 340/146.3 MA, 340/146.3 R
• US Class Current: 382/258
• CPC Class Codes: G06T 11/203 Drawing of straight lines or curves
• CPC Class Codes: G06V 30/10 Character recognition
• CPC Class Codes: G06V 30/168 Smoothing or thinning of the pattern; Skeletonisation

Abstract

Line portions of the character pattern in a character recognition device which have a thickness less than a selected standard value are thickened by a thickening circuit to the selected value. The line thickness of the character is then uniformly thinned by a thinning circuit and the thickening process is repeated. A correction circuit may be provided to prevent the continuity of the character from being broken in the thinning circuit.

Claims

1. In a character recognition system in which a document on which a character is printed is scanned and a character pattern representing the scanned document is obtained in the form of electrical signals arranged in a matrix of rows and columns constituting a quantized representation of the scanned document, the system being operative to compare the character pattern with at least one known character pattern to determine the degree of correspondence therewith, a line thickness regularizing device, comprising:

thickening means operative to sense the electrical signals representing the character pattern and thicken the line thickness of a portion of the character having a line thickness less than a predetermined value to the predetermined value by modifying the electrical signals;

thinning means operative to sense the electrical signals representing the charactter pattern and uniformly thin the line thickness of the character by modifying the electrical signals;

control means operative to control said thickening and thinning means so that the electrical signals are sequentially operated upon by the thickening means, the thinning means and again by the thickening means; and

correction means arranged to operate on the electrical signals before operation thereon by said thinning means, said correction means being operative to thicken the line thickness of a portion of the character so that the line continuity of the character will be maintained while the electrical signals are operated upon by the thinning means.

2. A device according to claim 1, further comprising storage means to store the electrical signals representing the character pattern in the form of the matrix, said storage means being operatively connected to said control means and said thickening and thinning means.

3. A device according to claim 2, in which said storage means is controllable by said control means to shift the character pattern therewithin in one direction.

4. A device according to claim 3, in which said thickening means comprises a plurality of thickening units each arranged to sense and thicken the line thickness of said line portion of the character in both the vertical and horizontal dimensions, said thickening units being connected to said storage means on a line perpendicular to the direction of shift of the character pattern.

5. A device according to claim 3, in which said thinning means comprises a plurality of thinning units each arranged to sense and thin the line thickness of the character, said thinning units being connected to said storage means on a line perpendicular to the direction of shift of the character pattern.

6. A device according to claim 2, in which said correction means comprises a plurality of correction units each arranged to sense the character pattern and thicken the line portion of the character so that line continuity of the character will be maintained during operation thereon by said thinning means, said correction units being controlled by said control means to operate on the character pattern after said thickening means and before said thinning means, and said correction units being connected to said storage means on a line perpendicular to the direction of shift of the character pattern.

7. A device according to claim 4, in which at least one of said thickening units comprises a vertical thickening unit and a horizontal thickening unit, said vertical thickening unit being connected to said storage means to sense the contents of said storage means representing a selected point in the matrix and points in the lines above and below the selected point, and being arranged to feed an electrical signal to said storage means to cause the contents of said storage means representing the point in the matrix directly above the selected point to represent a point on the character when the selected point represents a point on the character and a weighted value of the sum of the sensed contents of said storage means representing the points in the line above the selected point is greater than a weighted value of the sum fo the sensed contents of said storage means representing the points in the line below the selected point, and to feed an electrical signal to said storage means to cause the contents of said storage means representing the point in the matrix directly below the sensed point to represent a point on the character when the sensed point represents a point on the character and the weighted value of the sum of the sensed contents of said storage means representing the points in the line above the selected point is one of less than and equal to the weighted value of the sum of the sensed contents of said storage means representing the points in the line below the selected point.

8. A device according to claim 7, in which said horizontal thickening unit is connected to said storage means to sense the contents of said storage means representing the selected point in the matrix and points in the lines to the left and right of the selected point, and is arranged to feed an electrical signal to said storage means to cause the contents of said storage means representing the point in the matrix directly to the left of the selected point to represent a point on the character when the selected point represents a point on the character and a weighted value of the sum of the sensed contents of said storage means representing the points on the line to the left of the selected point is greater than a weighted value of the sum of the sensed contents of said storage means representing the points in the line to the right of the selected point, and to feed an electrical signal to said storage means to cause the contents of said storage means representing the point in the matrix directly to the right of the sensed point to represent a point on the character when the sensed point represents a point on the character and the weighted value of the sum of the sensed contents of said storage means representing the points in the line to the left of the selected point is one of less than and equal to the weighted value of the sum of the sensed contents of said storage means representing the points in the line to the right of the selected point.

9. A device according to claim 5, in which at least one of said thinning units is connected to said storage means to sense the contents of said storage means representing a selected point in the matrix and a point in the matrix diagonally adjacent to the selected point, and is arranged to feed an electrical signal to said storage means to cause the contents of said storage means representing the selected point to represent a point on the background of the character pattern when both of the sensed contents of said storage means represent points on the character.

10. A device according to claim 9, in which the point diagonally adjacent to the selected point is above and to the left of the selected point.

11. A device according to claim 6, in which at least one of said correction units is connected to said storage means to sense the contents of said storage means representing the points directly to the right of, below to the upper right and to the lower left of the selected point in the matrix, and is arranged to feed an electrical signal to said storage means to cause the contents of said storage means representing the selected point to represent a point on the character when all of the sensed contents represent points on the character.

12. A device according to claim 7, in which said vertical thickening unit comprises:

a comparator having one input connected to the points in said storage means representing the points in the line above the selected point in the matrix, said comparator having another input connected to the points in said storage means representing the points in the line below the selected point, each of said points in said storage means being connected to the respective input of said comparator through a respective resistor;

a first AND gate having one input connected to the output of said comparator and another input connected to the point in said storage means representing the selected point, the output of said first AND gate being connected to the point in said storage means representing the point in the matrix directly above the selected point; and

a second AND gate having one input connected through an inverter to the output of said comparator and a second input connected to the point in said storage means representing the selected point, the output os said second AND gate being connected to the point in said storage means representing the point in the matrix directly below the selected point.

13. A device according to claim 8, in which said horizontal thickening unit comprises:

a comparator having one input connected to the points in said storage means representing the points in the line to the left of the selected point in the matrix, said comparator having another input connected to the points in said storage means representing the points in the line to the right of the selected point, each of said points in said storage means being connected to the respective input of said comparator through a respective resistor;

a first AND gate having one input connected to the output of said comparator and another input connected to the point in said storage means representing the selected point, the output of said first AND gate being connected to the point in said storage means representing the point in the matrix directly to the left of the selected point; and

a second AND gate having one input connected through an inverter to the output of said comparator and a second input connected to the point in said storage means representing the selected point, the output of said second AND gate being connected to the point in said storage means representing the point in the matrix directly to the right of the selected point.

14. A device according to claim 9, in which said thinning unit comprises an AND gate having one input connected to the point in said storage means representing the selected point and another input connected to the point in said storage means representing the point diagonally adjacent to the selected point, the output of said AND gate being connected to the point in said storage means constituting a reset input for the contents of said storage means representing the selected point.

15. A device according to claim 11, in which said correction unit comprises an AND gate having inputs connected respectively to points in said storage means representing the points in the matrix to the right, below, to the upper right and to the lower left of the selected point, the output of said AND gate being connected to a point in said storage means representing the selected point.

16. A device according to claim 3, in which said storage means comprises:

a main memory in the form of a plurality of shift registers, each shift register storing a line of the matrix and being shiftable in the horizontal direction;

a first auxiliary memory in the form of a plurality of shift registers, the number of said shift registers in said first auxiliary memory being equal to the number of said shift registers in said main memory, and the inputs of said shift registers of said first auxiliary memory being connected respectively to the outputs of said shift registers of said main memory;

a second auxiliary memory in the form of a plurality of shift registers, the number of said shift registers of said second auxiliary memory being equal to the number of said shift registers of said main memory, the inputs of said shift registers of said second auxiliary memory being connected respectively to the outputs of said shift registers of said main memory and the outputs of said shift register of said second auxiliary memory being connected respectively to the inputs of said shift registers of said main memory;

said thickening means being in the form of a plurality of thickening units, the number of said thickening units being equal to the number of said shift registers of said main memory, the inputs of said thickening units being connected respectively to points in said shift registers of said first auxiliary memory in a vertical arrangement and the outputs of said thickening units being connected respectively to points in said shift registers of said second auxiliary memory in a vertical arrangement representing the same points in the matrix as the points in said first auxiliary memory; and

said thinning means being in the form of a plurality of thinning units having inputs and outputs connected respectively to the same points in said storage means as said thickening units;

said control means being operative to sequentially activate said thickening means, said thinning means, and again said thickening means while shifting the character pattern through said storage means.