do_ocr_word_svmdo_ocr_word_svmdo_ocr_word_svmDoOcrWordSvmDoOcrWordSvm (Operator)

Name

do_ocr_word_svmdo_ocr_word_svmdo_ocr_word_svmDoOcrWordSvmDoOcrWordSvm — Classify a related group of characters with an OCR classifier.

Signature

Description

do_ocr_word_svmdo_ocr_word_svmdo_ocr_word_svmDoOcrWordSvmDoOcrWordSvm works like do_ocr_multi_class_svmdo_ocr_multi_class_svmdo_ocr_multi_class_svmDoOcrMultiClassSvmDoOcrMultiClassSvm insofar as it computes the best class for each of the characters given by the regions CharacterCharacterCharacterCharactercharacter and the gray values ImageImageImageImageimage with the OCR classifier OCRHandleOCRHandleOCRHandleOCRHandleOCRHandle, and returns the results in ClassClassClassClassclassVal.

In contrast to do_ocr_multi_class_svmdo_ocr_multi_class_svmdo_ocr_multi_class_svmDoOcrMultiClassSvmDoOcrMultiClassSvm, do_ocr_word_svmdo_ocr_word_svmdo_ocr_word_svmDoOcrWordSvmDoOcrWordSvm treats the group of characters as an entity which yields a WordWordWordWordword by concatenating the class names for each character region. This allows to restrict the allowed classification results on a textual level by specifying an ExpressionExpressionExpressionExpressionexpression describing the expected word.

The ExpressionExpressionExpressionExpressionexpression may restrict the word to belong to a predefined lexicon created using create_lexiconcreate_lexiconcreate_lexiconCreateLexiconCreateLexicon or import_lexiconimport_lexiconimport_lexiconImportLexiconImportLexicon, by specifying the name of the lexicon in angular brackets as in '<mylexicon>'"<mylexicon>""<mylexicon>""<mylexicon>""<mylexicon>". If the ExpressionExpressionExpressionExpressionexpression is of any other form, it is interpreted as a regular expression with the same syntax as specified for tuple_regexp_matchtuple_regexp_matchtuple_regexp_matchTupleRegexpMatchTupleRegexpMatch. Note that you will usually want to use an expression of the form '^...'$'"$""$""$""$"' when using variable quantifiers like '*', to ensure that the entire word is used in the expression. Also note that in contrast to tuple_regexp_matchtuple_regexp_matchtuple_regexp_matchTupleRegexpMatchTupleRegexpMatch, do_ocr_word_svmdo_ocr_word_svmdo_ocr_word_svmDoOcrWordSvmDoOcrWordSvm does not support passing extra options in an expression tuple.

If the word derived from the best class for each character does not match the ExpressionExpressionExpressionExpressionexpression, do_ocr_word_svmdo_ocr_word_svmdo_ocr_word_svmDoOcrWordSvmDoOcrWordSvm attempts to correct it by considering the NumAlternativesNumAlternativesNumAlternativesNumAlternativesnumAlternatives best classes for each character. The alternatives used are identical to those returned by do_ocr_single_class_svmdo_ocr_single_class_svmdo_ocr_single_class_svmDoOcrSingleClassSvmDoOcrSingleClassSvm for a single character. It does so by testing all possible corrections for which the classification result is changed for at most NumCorrectionsNumCorrectionsNumCorrectionsNumCorrectionsnumCorrections character regions.

In case the ExpressionExpressionExpressionExpressionexpression is a lexicon and the above procedure did not yield a result, the most similar word in the lexicon is returned as long as it requires less than NumCorrectionsNumCorrectionsNumCorrectionsNumCorrectionsnumCorrections edit operations for the correction (see suggest_lexiconsuggest_lexiconsuggest_lexiconSuggestLexiconSuggestLexicon).

The resulting word is graded by a ScoreScoreScoreScorescore between 0.0 (no correction found) and 1.0 (original word correct), which is dominated by the number of corrected characters but also adds a minor penalty for ignoring the second best class or even all best classes (in case of lexica).

Parallelization

• Multithreading type: reentrant (runs in parallel with non-exclusive operators).
• Multithreading scope: global (may be called from any thread).
• Processed without parallelization.

Parameters

Complexity

The complexity of checking all possible corrections is of magnitude O((n*a)^min(c,n)), where a is the number of alternatives, n is the number of character regions, and c is the number of allowed corrections. However, to guard against a near-infinite loop in case of large n, c is internally clipped to 5, 3, or 1 if a*n >= 30, 60, or 90, respectively.

Result

If the parameters are valid, the operator do_ocr_multi_class_svmdo_ocr_multi_class_svmdo_ocr_multi_class_svmDoOcrMultiClassSvmDoOcrMultiClassSvm returns the value 2 (H_MSG_TRUE). If necessary an exception is raised.

Possible Predecessors

trainf_ocr_class_svmtrainf_ocr_class_svmtrainf_ocr_class_svmTrainfOcrClassSvmTrainfOcrClassSvm, read_ocr_class_svmread_ocr_class_svmread_ocr_class_svmReadOcrClassSvmReadOcrClassSvm

Alternatives

do_ocr_multi_class_svmdo_ocr_multi_class_svmdo_ocr_multi_class_svmDoOcrMultiClassSvmDoOcrMultiClassSvm

See also

create_ocr_class_svmcreate_ocr_class_svmcreate_ocr_class_svmCreateOcrClassSvmCreateOcrClassSvm, classify_class_svmclassify_class_svmclassify_class_svmClassifyClassSvmClassifyClassSvm

Module

OCR/OCV