Method of and device for identifying direction of characters in image block

1. A method of identifying the direction of characters in an image block, comprising:

performing optical character recognition processing on the image block by assuming various directions as assumed character directions, respectively, to obtain sub image blocks, recognized characters corresponding to the sub image blocks and correctness measures thereof in each of the assumed character directions;

determining a language group to which the characters in the image block belong;

adjusting a correctness measure corresponding to a sub image block which corresponds to a recognized character not belonging to the determined language group in each of the assumed character directions;

calculating an accumulative correctness measure in each of the assumed character directions based on the adjusted correctness measure; and

identifying the direction of the characters in the image block according to the accumulative correctness measures.

2. The method according to claim 1 , wherein:

said correctness measure comprises a confidence and a recognition distance; and

said adjusting a correctness measure corresponding to a sub image block which corresponds to a recognized character not belonging to the determined language group in each of the assumed character directions comprises one of decreasing the confidence corresponding to the sub image block and increasing the recognition distance corresponding to the sub image block.

3. The method according to claim 1 , wherein:

said correctness measure comprises a confidence and a recognition distance; and

said adjusting a correctness measure corresponding to a sub image block which corresponds to a recognized character not belonging to the determined language group in each of the assumed character directions comprises adjusting one of the confidence and the recognition distance corresponding to the sub image block to one of the maximum confidence among confidences corresponding to all of the candidate characters that belong to the determined language group in the assumed character direction and correspond to the sub image block and a minimum recognition distance among recognition distances corresponding to all of the candidate characters that belong to the determined language group in the assumed character direction and correspond to the sub image block, and, when none of the candidate characters in the assumed character direction which correspond to the sub image block belong to the determined language group, taking one of the minimum confidence among confidences corresponding to all of the candidate characters in the assumed character direction which correspond to the sub image block and the maximum recognition distance among recognition distances corresponding to all of the candidate characters in the assumed character direction which correspond to the sub image block as one of the confidence and the recognition distance corresponding to the sub image block.

4. The method according to claim 1 , wherein said determining a language group to which the characters in the image block belong comprises:

in each of the assumed character directions, calculating a proportion of sub image blocks corresponding to recognized characters which belong to each of the language groups in all of the sub image blocks in the assumed character direction, respectively; and

when the proportion of sub image blocks corresponding to recognized characters which belong to a certain language group in all of the sub image blocks in the assumed character direction is larger than a first threshold, determining the language group as the language group to which the characters in the image block belong.

5. The method according to claim 1 , wherein said determining a language group to which the characters in the image block belong comprises:

in each of the assumed character directions, calculating a proportion of the sub image blocks corresponding to recognized characters which belong to each of the language groups in all of the sub image blocks in the assumed character direction, respectively; and

when the proportion of sub image blocks corresponding to recognized characters which belong to a certain language group in all of the sub image blocks in the assumed character direction is larger than a first threshold and the proportion of sub image blocks corresponding to recognized characters which belong to a core character set of the language group in all of the sub image blocks in the assumed character direction is larger than a second threshold, determining the language group as the language group to which the characters in the image block belong.

6. The method according to claim 4 , wherein the language group comprises a Latin language group;

the Latin language group comprises Latin letters, Arabic numerals and non-character symbols; and

a value range of the first threshold is (0.65, 0.85).

7. The method according to claim 5 , wherein the language group comprises a Korean language group and a Chinese/Japanese language group;

the Korean language group comprises Korean letters, Latin letters, Arabic numerals and non-character symbols, and a core character set of the Korean language group comprises Korean letters;

the Chinese/Japanese language group comprises simplified Chinese characters, traditional Chinese characters, Chinese characters in Japanese, Japanese hiragana, Japanese katakana, Latin letters, Arabic numerals and non-character symbols, and a core character set of the Chinese/Japanese language group comprises simplified Chinese characters, traditional Chinese characters, Chinese characters in Japanese, Japanese hiragana and Japanese katakana; and

a value range of the first threshold is (0.65, 0.85), and a value range of the second threshold is (0.45, 0.65).

8. The method according to claim 1 , wherein the various directions comprise two transverse directions and two longitudinal directions of the image block.

9. A device for identifying the direction of characters in an image block, comprising:

an optical character recognition processing unit configured for performing optical character recognition processing on the image block by assuming various directions as assumed character directions, respectively, to obtain sub image blocks, recognized characters corresponding to the sub image blocks and correctness measures thereof in each of the assumed character directions;

a language group determination unit configured for determining a language group to which the characters in the image block belong;

a sub image block adjusting unit configured for adjusting a correctness measure corresponding to a sub image block which corresponds to a recognized character not belonging to the determined language group in each of the assumed character directions;

an accumulative correctness measure calculating unit configured for calculating an accumulative correctness measure in each of the assumed character directions based on the adjusted correctness measure; and

a character direction identifying unit configured for identifying the direction of the characters in the image block according to the accumulative correctness measures.

10. The device according to claim 9 , wherein the sub image block adjusting unit is configured for one of decreasing the confidence corresponding to a sub image block which corresponds to a recognized character not belonging to the determined language group in each of the assumed character directions and increasing the recognition distance corresponding to the sub image block.

11. The device according to claim 9 , wherein the sub image block adjusting unit is configured for adjusting one of the confidence and the recognition distance corresponding to a sub image block which corresponds to a recognized character not belonging to the determined language group in each of the assumed character directions to one of the maximum confidence among confidences corresponding to all of the candidate characters that belong to the determined language group in the assumed character direction and correspond to the sub image block and a minimum recognition distance among recognition distances corresponding to all of the candidate characters that belong to the determined language group in the assumed character direction and correspond to the sub image block, and, when none of the candidate characters in the assumed character direction which correspond to the sub image block belong to the determined language group, taking one of the minimum confidence among confidences corresponding to all of the candidate characters in the assumed character direction which correspond to the sub image block and the maximum recognition distance among recognition distances corresponding to all of the candidate characters in the assumed character direction which correspond to the sub image block as the one of confidence and the recognition distance corresponding to the sub image block.

12. The device according to claim 9 , wherein the language group determination unit is configured for in each of the assumed character directions, calculating the proportion of sub image blocks corresponding to recognized characters which belong to each of the language groups in all of the sub image blocks in the assumed character direction, respectively; and when the proportion of sub image blocks corresponding to recognized characters which belong to a certain language group in all of the sub image blocks in the assumed character direction is larger than a first threshold, determining the language group as the language group to which the characters in the image block belong.

13. The device according to claim 9 , wherein the language group determination unit is configured for in each of the assumed character directions, calculating a proportion of the sub image blocks corresponding to recognized characters which belong to each of the language groups in all of the sub image blocks in the assumed character direction, respectively; and when the proportion of sub image blocks corresponding to recognized characters which belong to a certain language group in all of the sub image blocks in the assumed character direction is larger than a first threshold and the proportion of sub image blocks corresponding to recognized characters which belong to a core character set of the language group in all of the sub image blocks in the assumed character direction is larger than a second threshold, determining the language group as the language group to which the characters in the image block belong.

14. A scanner comprising the device for identifying the direction of characters in an image block according to claim 9 .