Code detection and decoding system
A method ( 2304 ) of decoding a QR code having two initially detected finder patterns ( 2901, 2902; 2911, 2912 ) is provided. The method forms ( 2402 ) a pattern matching template ( 2700, 2800 ) based on characteristics of the detected finder patterns and determines ( 2403 ) at least one candidate region ( 2904, 2905; 2913, 2914 ) about the detected finder patterns. The candidate region is typically based at least on the relative positions of the detected finder patterns. The method detects ( 2404 ) a previously undetected third finder pattern of the QR code in the at least one candidate region by correlating content of the candidate region with the pattern matching template. With the identified third finder pattern and each of the two initially detected finder patterns, decoding ( 2305 ) the QR code can then be performed. Also disclosed is a method of detecting a two-dimensional code comprising known target features and coded data in an image. The target features comprise a continuous black region, enclosed entirely by a continuous white region, enclosed entirely by a continuous black region. The method performs line-by-line connected component analysis ( 403 ) of the image to determine candidate features of interest. The line-by-line connected component analysis aggregates metrics corresponding to candidate features of interest. The method evaluates ( 404 ) the aggregated metrics to determine how similar each candidate feature of interest is to the target feature and forms ( 405 ) a candidate region of interest from multiple candidate features of interest. Typically the target features include the copyright symbol © and the registered trade mark symbol ®.
1. A computer implemented method of decoding a QR code having only two initially detected finder patterns, the detection corresponding to determining the existence of the finder patterns in the QR code, the computer including at least a processor for executing the method and an associated memory in which an image including the finder patterns is stored, said method comprising the steps of:
(a) acquiring a pattern matching template based on characteristics of the detected finder patterns;
(b) determining at least one candidate region about the detected finder patterns, the candidate region being based at least on the relative positions of the detected finder patterns in the QR code;
(c) locating a previously undetected third finder pattern of the QR code in the at least one candidate region by correlating content of the candidate region with the pattern matching template; and
(d) decoding the QR code with each of the two initially detected finder patterns and the third finder pattern.
2. A method according to claim 1 wherein the two initially detected finder patterns are detected using connected component analysis.
3. A method according to claim 1 wherein the characteristics of the detected finder patterns comprise angle of rotation and module size.
4. A method according to claim 3 wherein the characteristics of the detected finder patterns further include black and white module sizes.
5. A method according to claim 1 wherein the characteristics of the detected finder patterns are based on the intensity values of pixels of at least one of the detected finder patterns.
6. A method according to claim 1 wherein step (d) comprises decoding the QR code with the location of the third finder pattern and the locations of the two initially detected finder patterns.
7. A computer readable storage medium having a computer program recorded thereon, the program being executable by computer apparatus to decode a QR code having only two initially detected finder patterns, the detection corresponding to determining the existence of the finder patterns in the QR code, said program comprising:
code for acquiring a pattern matching template based on characteristics of the detected finder patterns;
code for determining at least one candidate region about the detected finder patterns, the candidate region being based at least on the relative positions of the detected finder patterns in the QR code;
code for locating a previously undetected third finder pattern of the QR code in the at least one candidate region by correlating content of the candidate region with the pattern matching template; and
code for decoding the QR code with each of the two initially detected finder patterns and the third finder pattern.
8. A computer readable storage medium according to claim 7 wherein the two initially detected finder patterns are detected using connected component analysis.
9. A computer readable storage medium according to claim 7 wherein the characteristics of the detected finder patterns comprise angle of rotation and module size.
10. A computer readable storage medium according to claim 9 wherein the characteristics of the detected finder patterns further include black and white module sizes.
11. A computer readable storage medium according to claim 8 wherein the characteristics of the detected finder patterns are based on the intensity values of pixels of at least one of the detected finder patterns.
12. A computer readable storage medium according to claim 7 wherein said code for decoding comprises code for decoding the QR code with the location of the third finder pattern and the locations of the two initially detected finder patterns.
13. Computer apparatus adapted for decoding a QR code having only two initially detected finder patterns, the detection corresponding to determining the existence of the finder patterns in the QR code, said apparatus comprising:
means for acquiring a pattern matching template based on characteristics of the detected finder patterns;
means for determining at least one candidate region about the detected finder patterns, the candidate region being based at least on the relative positions of the detected finder patterns in the QR code;
means for locating a previously undetected third finder pattern of the QR code in the at least one candidate region by correlating content of the candidate region with the pattern matching template; and
means for decoding the QR code with each of the two initially detected finder patterns and the third finder pattern.