Method and system for creating and using barcodes
Methods for efficiently retrieving information from an image of a symbol are described. Symbols are described that contain detection patterns that facilitate the determination of location, alignment, size and orientation of the symbol in an image. Detection patterns are described that possess geometric shapes susceptible to efficient decoding using probabilistic detection algorithms. Detection patterns are described that are provided in colors, shapes and sizes different from the color, shape and sizes of modules carrying information in the symbol. Methods are described for identifying the location and size of detection patterns in images of the symbol and for locating modules in the symbol to facilitate extraction of information carried by the modules.
1. A method, comprising:
detecting, within a two-dimensional barcode comprising a plurality of square modules that collectively encode information, at least one circular finder pattern that is centered or substantially centered at a reference point within the two-dimensional barcode;
detecting at least one circular alignment pattern that is located within the two-dimensional barcode according to a geometric relationship with the at least one circular finder pattern; and
determining an alignment of the two-dimensional barcode based on detected locations of the at least one circular finder pattern and the at least one circular alignment pattern.
2. The method of claim 1 , wherein the detecting the at least one circular alignment pattern comprises detecting boundary points of the at least one circular alignment pattern on a set of angularly displaced scan lines that intersect at a starting point within the two-dimensional barcode.
3. The method of claim 1 , wherein the detecting the at least one circular alignment pattern further comprises:
selecting a first maximum size of the at least one circular alignment pattern;
determining, based on the first maximum size, a first set of starting points within the two-dimensional barcode; and
searching for the at least one circular alignment pattern based on the first set of starting points as parameters.
4. The method of claim 3 , further comprising:
in response to the searching not detecting the at least one circular alignment pattern,
selecting a second maximum size of the at least one circular alignment pattern, wherein the second maximum size is smaller than the first maximum size;
determining, based on the second maximum size, a second set of starting points within the two-dimensional barcode; and
re-searching for the at least one circular alignment pattern based on the second set of starting points as the parameters.
5. The method of claim 1 , wherein the detecting the at least one circular alignment pattern comprises detecting the at least one circular alignment pattern based on a color differentiation between the at least one circular alignment pattern and the plurality of square modules.
6. The method of claim 1 , further comprising:
detecting at least one position detection pattern within the two-dimensional barcode; and
determining a position of the two-dimensional barcode based on a location determined for the at least one position detection pattern.
7. The method of claim 1 , further comprising:
detecting at least one orientation pattern within the two-dimensional barcode; and
determining an orientation of the two-dimensional barcode based on a location determined for the at least one orientation pattern.
8. The method of claim 1 , wherein the detecting the at least one circular alignment pattern comprises searching for the at least one circular alignment pattern within an area of the two-dimensional barcode, wherein the area is selected based on a radius determined for the at least one circular finder pattern.
9. The method of claim 1 , further comprising determining a location of a square module of the plurality of square modules based on dividing a distance between two neighboring alignment patterns of the at least one circular alignment pattern.
10. A system, comprising:
a barcode reader configured to
scan a symbol comprising a plurality of square modules that collectively encode information,
detect, within the symbol, at least one circular finder pattern that is centered or substantially centered at a reference point within the symbol and at least one circular alignment pattern that is located within the symbol according to a geometric relationship with the at least one circular finder pattern, and
determine an alignment of the symbol based on determined locations of the at least one circular finder pattern and the at least one circular alignment pattern.
11. The system of claim 10 , wherein the barcode reader is further configured to identify boundary points of the at least one circular alignment pattern on a plurality of angularly displaced scan lines that intersect at a starting point within the symbol.
12. The system of claim 10 , wherein the barcode reader is further configured to
select a first size limit for the at least one circular alignment pattern,
determine, based on the first size limit, a first plurality of starting points within the symbol, and
perform a first search for the at least one circular alignment pattern using the first plurality of starting points as first search parameters.
13. The system of claim 12 , wherein the barcode reader is further configured to
select a second size limit for the at least one circular alignment pattern in response to a determination that the first search does not detect the at least one circular alignment pattern, wherein the second size limit is smaller than the first size limit,
determine, based on the second size limit, a second plurality of starting points within the symbol, and
perform a second search for the at least one circular alignment pattern using the second plurality of starting points as second search parameters.
14. The system of claim 10 , wherein the barcode reader is further configured to detect the at least one circular alignment pattern based in part on a color difference between the at least one circular alignment pattern and the plurality of square modules.
15. The system of claim 10 , wherein the barcode reader is further configured to detect at least one position detection pattern within the symbol.
16. The system of claim 10 , wherein the barcode reader is further configured to detect at least one orientation pattern within the symbol.
17. A computer-readable storage medium comprising computer-executable instructions that, in response to execution, cause a computing system comprising a processor to perform operations, comprising:
locating, based on a scan of a two-dimensional barcode comprising square modules that collectively encode information, at least one circular finder pattern that is centered or substantially centered at a reference point within the two-dimensional barcode;
locating, based on the scan, at least one circular alignment pattern that is located within the two-dimensional barcode according to a geometric relationship with the at least one circular finder pattern; and
determining an alignment of the two-dimensional barcode based on respective locations of the at least one circular finder pattern and the at least one circular alignment pattern.
18. The computer-readable storage medium of claim 17 , wherein the locating the at least one circular alignment pattern comprises locating boundary points of the at least one circular alignment pattern on a set of angularly displaced scan lines that intersect at a starting point defined within the two-dimensional barcode.
19. A system, comprising:
means for detecting, within a symbol that encodes information as a plurality of square modules, at least one circular finder pattern that is centered or substantially centered at a reference point within the two-dimensional barcode and at least one circular alignment pattern that is located within the two-dimensional barcode according to a geometric relationship with the at least one circular finder pattern; and
means for determining an alignment of the symbol based on respective locations of the at least one circular finder pattern and the at least one circular alignment pattern.
20. The system of claim 19 , wherein the means for detecting comprises means for detecting a color differentiation between the at least one alignment pattern and the plurality of square modules.