Method of decoding a symbol with a low contrast

• US 7,311,262 B2
• Filed: 08/09/2004
• Issued: 12/25/2007
• Est. Priority Date: 08/09/2004
• Status: Expired due to Fees

• Current Assignee: Optoelectronics Co Limited (Optoelectronics)
• Original Assignee: Optoelectronics Co Limited (Optoelectronics)
• Inventors: Hosoi, Kazukuni, Matsuoka, Haruo
• Primary Examiner(s): Lee; Michael G.
• Assistant Examiner(s): Kim; Tae W.
• Application Number:
  US10/914,347
• Publication Number:
  US 20060027661A1
• Time in Patent Office: 1,233 Days
• Field of Search: 235/462.25
• US Class Current: 235/462.25
• CPC Class Codes: G06K 7/10851 Circuits for pulse shaping, amplifying, eliminating noise signals, checking the function of the sensing device basic electronic circuitry H03
• CPC Class Codes: G06K 7/1095 the scanner comprising adaptations for scanning a record carrier that is displayed on a display-screen or the like
• CPC Class Codes: G06K 7/1478 adapting the threshold for pixels in a CMOS or CCD pixel sensor for black and white recognition

Abstract

A method for encoding a symbol such as a barcode with a finder of a known pattern, comprises steps of determining a potential point on the finder edge and tracing and verifying a path representing the finder edge by checking the color of each point on the path against a threshold. The threshold is preferably reevaluated at least every several pixel movements along the path. The method may decode the barcode directly from the gray image displayed on a LCD screen without a need of a whole characterized image.

Claims

1. A method for finding an edge of a finder of a symbol in an image, said symbol being represented by points of either a dark color or a light color and having one or more of said finders of a known pattern, said method comprising steps of:

a) picking up data on a line possibly crossing an edge of a potential finder of said symbol, and calculating a runlength on the line;

b) determining a potential point of said edge on said line where a color change occurs in said calculated runlength;

c) determining a path extending from said potential point representing said edge according to said known pattern of said finder; and

d) verifying whether said path is actually said edge said verifying comprising checking whether each point on said path is of the dark or white color by recalculating a threshold at least every predetermined amount of said point(s) and comparing each subsequent point to said recalculable threshold.

2. The method of claim 1, wherein said step d) comprising calculating said threshold at a point on said path and applying said threshold for next points along said path.

3. The method of claim 2, wherein said threshold is reevaluated every several points.

4. The method of claim 1, wherein step a) is repeated at a next line if no said potential point can be determined at step b).

5. The method of claim 1, wherein step b) is repeated at a next potential point on said line if said path is verified as not said edge at step d).

6. The method of claim 1, wherein said image is an original gray image.

7. The method of claim 6, wherein said image is displayed on a LCD screen of a device.

8. The method of claim 7, wherein said device is a mobile phone.

9. The method of claim 1, wherein said symbol is a barcode.

10. The method of claim 9, wherein said barcode is a two-dimensional barcode.

11. The method of claim 10, wherein said barcode is a Data Matrix bar code.

12. The method of claim 11, wherein said edge is one of two solid perimeter edges of the symbol.

13. The method of claim 11, wherein said edge is one of two alternative-colored perimeter edges of the symbol.

14. The method of claim 1, wherein said dark color is a black color and said light color is a white color.

15. The method of claim 14, wherein said light color is similar to background color of said image.

16. The method of claim 1, wherein said color change in said step b) is a change from a color similar to a background color of said image to a color in contrast to said background.

17. The method of claim 1, wherein said step d) comprising checking whether a color change expected from the known finder pattern occurs at each point on said path.

18. A method for decoding a symbol having one or more finders of a known-pattern, said symbol being represented by points of either a dark color or a light color, said method comprising the steps of:

a) picking up data on a line possibly crossing an edge of a potential finder of said symbol, and calculating a runlength on the line;

b) determining a potential point of said edge on said line where a color changes in said calculated runlength;

c) determining a path extending from said potential point representing said edge according to said known pattern of said finder;

d) verifying whether said path is actually said edge, comprises checking, by recalculating a threshold at least every predetermined amount of said point(s) and comparing each subsequent point with said recalculable threshold, whether each of the points on said path has an expected color determined from the pattern of the finder;

e) repeating said steps a)-d) to find all of said finders on said symbol; and

f) binarizing and decoding said symbol with said found finders only if said finders are found.

19. The method of claim 18, wherein said verifying step d) comprising calculating said threshold at a point on said path and applying said threshold for next points along said path.

20. The method of claim 19, wherein said threshold is calculated at least every several points.

21. The method of claim 20, wherein said symbol is a barcode displayed on a LCD screen.

22. The method of claim 21, wherein said steps a)-f) are carried out directly from gray data obtained from the barcode.

23. The method of claim 22, wherein said barcode is a Data Matrix barcode.

24. A method for decoding a barcode having a finder of a known pattern, comprising steps of

along a predetermined path tracing and verifying a potential edge of said finder by recalculating a threshold at least every predetermined amount of said point(s), checking a color of each subsequent point on said potential edge against said recalculable threshold, and binarizing and filtering said barcode only after said finder pattern is found.

25. The method of claim 24, wherein said threshold is calculated at a point and applied to next points along said potential edge.

26. The method of claim 25, wherein said threshold is recalculated at least every several points.

27. The method of claim 26, wherein said threshold is recalculated at each point and applied to a next point.