Method of and device for identifying direction of characters in image block
The embodiments disclose a method of and a device for identifying direction of characters in image block. The method includes: performing optical character recognition processing on the image block by assuming various directions as assumed character directions to obtain sub image blocks, recognized characters and correctness measures in each assumed direction; in sub image blocks in the assumed directions with a 180° mutual relation, searching for a minimum matching pair; when there is one sub image block in each assumed direction in a minimum matching pair and recognized characters belonging to the minimum matching pair are the same rotation invariant character or belong to the same rotation invariant character pair, adjusting their correctness measures to the same; calculating an accumulative correctness measure in each assumed direction based on the adjusted results; and identifying the direction of the characters in the image block according to the accumulative correctness measures.
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;
in sub image blocks in the assumed character directions with a 180° mutual relation therebetween, searching for a minimum matching pair of the sub image blocks, wherein the minimum matching pair is two sets of sub image blocks in the assumed character directions with a 180° mutual relation therebetween, which have corresponding positions, identical sizes and a minimum number of sub image blocks;
when there is one sub image block in each of the two assumed character directions in a minimum matching pair and recognized characters corresponding to the two sub image blocks belonging to the minimum matching pair are the same rotation invariant character or belong to the same rotation invariant character pair, adjusting the correctness measures corresponding to the two sub image blocks to the same numerical value;
calculating an accumulative correctness measure in each of the assumed character directions based on the adjusted sub image blocks; 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:
the rotation invariant character comprises a character with a spin symmetry of 180°, i.e., the rotation invariant character becomes itself after being rotated by 180°; and
the rotation invariant character pair comprises two characters, any one of which becomes consistent with or has a high similarity in shape to the other one after being rotated by 180°.
3. The method according to claim 1 , wherein said adjusting the correctness measures corresponding to the two sub image blocks to the same numerical value comprises adjusting the correctness measures corresponding to the two sub image blocks to an average value of the correctness measures corresponding to the two sub image blocks.
4. The method according to claim 1 , wherein said adjusting the correctness measures corresponding to the two sub image blocks to the same numerical value comprises adjusting the correctness measures corresponding to the two sub image blocks to one of the correctness measures corresponding to the two sub image blocks.
5. The method according to claim 1 , wherein the correctness measure comprises a confidence and a recognition distance; and the various directions comprise two transverse directions and two longitudinal directions of the image block.
6. The method according to claim 1 , wherein said calculating an accumulative correctness measure in each of the assumed character directions based on the adjusted sub image blocks comprises: taking a result of dividing a sum of the correctness measures of the adjusted sub image blocks in each of the assumed character directions by the number of the minimum matching pairs in the respective assumed character direction as the accumulative correctness measure in the respective assumed character direction.
7. 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 minimum matching pair searching unit configured for, in sub image blocks in the assumed character directions with a 180° mutual relation therebetween, searching for a minimum matching pair of the sub image blocks, wherein the minimum matching pair is two sets of sub image blocks in the assumed character directions with a 180° mutual relation therebetween, which have corresponding positions, identical sizes and a minimum number of sub image blocks;
a sub image block adjusting unit configured for, when there is one sub image block in each of the two assumed character directions in a minimum matching pair and the recognized characters corresponding to the two sub image blocks belonging to the minimum matching pair are the same rotation invariant character or belong to the same rotation invariant character pair, adjusting the correctness measures corresponding to the two sub image blocks to the same numerical value;
an accumulative correctness measure calculating unit configured for calculating an accumulative correctness measure in each of the assumed character directions based on the adjusted sub image blocks; and
a character direction identifying unit configured for identifying the direction of the characters in the image block according to the accumulative correctness measures.
8. The device according to claim 7 , wherein the sub image block adjusting unit is configured for, when there is one sub image block in each of the two assumed character directions in a minimum matching pair and recognized characters corresponding to the two sub image blocks belonging to the minimum matching pair are the same rotation invariant character or belong to the same rotation invariant character pair, adjusting the correctness measures corresponding to the two sub image blocks to an average value of the correctness measures corresponding to the two sub image blocks.
9. The device according to claim 7 , wherein the sub image block adjusting unit is configured for, when there is one sub image block in each of the two assumed character directions in a minimum matching pair and recognized characters corresponding to the two sub image blocks belonging to the minimum matching pair are the same rotation invariant character or belong to the same rotation invariant character pair, adjusting the correctness measures corresponding to the two sub image blocks to one of the correctness measures corresponding to the two sub image blocks.
10. The device according to claim 7 , wherein the accumulative correctness measure calculating unit is configured for taking a result of dividing a sum of the correctness measures of the adjusted sub image blocks in each of the assumed character directions by the number of the minimum matching pairs in the respective assumed character direction as the accumulative correctness measure in the respective assumed character direction.
11. A scanner comprising the device for identifying the direction of characters in an image block according to claim 7 .