cv::text Namespace Reference

Classes
class	BaseOCR
class	ERFilter
	Base class for 1st and 2nd stages of Neumann and Matas scene text detection algorithm [Neumann12]. : More...
struct	ERStat
	The ERStat structure represents a class-specific Extremal Region (ER). More...
class	OCRBeamSearchDecoder
	OCRBeamSearchDecoder class provides an interface for OCR using Beam Search algorithm. More...
class	OCRHMMDecoder
	OCRHMMDecoder class provides an interface for OCR using Hidden Markov Models. More...
class	OCRTesseract
	OCRTesseract class provides an interface with the tesseract-ocr API (v3.02.02) in C++. More...

Enumerations
enum	{   ERFILTER_NM_RGBLGrad,   ERFILTER_NM_IHSGrad }
	computeNMChannels operation modes More...
enum	{   OCR_LEVEL_WORD,   OCR_LEVEL_TEXTLINE }
enum	decoder_mode { OCR_DECODER_VITERBI = 0 }
enum	erGrouping_Modes {   ERGROUPING_ORIENTATION_HORIZ,   ERGROUPING_ORIENTATION_ANY }
	text::erGrouping operation modes More...

Functions
void	computeNMChannels (InputArray _src, OutputArrayOfArrays _channels, int _mode=ERFILTER_NM_RGBLGrad)
	Compute the different channels to be processed independently in the N&M algorithm [Neumann12]. More...
Ptr< ERFilter >	createERFilterNM1 (const Ptr< ERFilter::Callback > &cb, int thresholdDelta=1, float minArea=(float) 0.00025, float maxArea=(float) 0.13, float minProbability=(float) 0.4, bool nonMaxSuppression=true, float minProbabilityDiff=(float) 0.1)
	Create an Extremal Region Filter for the 1st stage classifier of N&M algorithm [Neumann12]. More...
Ptr< ERFilter >	createERFilterNM2 (const Ptr< ERFilter::Callback > &cb, float minProbability=(float) 0.3)
	Create an Extremal Region Filter for the 2nd stage classifier of N&M algorithm [Neumann12]. More...
void	createOCRHMMTransitionsTable (std::string &vocabulary, std::vector< std::string > &lexicon, OutputArray transition_probabilities_table)
	Utility function to create a tailored language model transitions table from a given list of words (lexicon). More...
Mat	createOCRHMMTransitionsTable (const String &vocabulary, std::vector< cv::String > &lexicon)
void	detectRegions (InputArray image, const Ptr< ERFilter > &er_filter1, const Ptr< ERFilter > &er_filter2, std::vector< std::vector< Point > > &regions)
void	erGrouping (InputArray img, InputArrayOfArrays channels, std::vector< std::vector< ERStat > > &regions, std::vector< std::vector< Vec2i > > &groups, std::vector< Rect > &groups_rects, int method=ERGROUPING_ORIENTATION_HORIZ, const std::string &filename=std::string(), float minProbablity=0.5)
	Find groups of Extremal Regions that are organized as text blocks. More...
void	erGrouping (InputArray image, InputArray channel, std::vector< std::vector< Point > > regions, std::vector< Rect > &groups_rects, int method=ERGROUPING_ORIENTATION_HORIZ, const String &filename=String(), float minProbablity=(float) 0.5)
Ptr< ERFilter::Callback >	loadClassifierNM1 (const String &filename)
	Allow to implicitly load the default classifier when creating an ERFilter object. More...
Ptr< ERFilter::Callback >	loadClassifierNM2 (const String &filename)
	Allow to implicitly load the default classifier when creating an ERFilter object. More...
Ptr< OCRBeamSearchDecoder::ClassifierCallback >	loadOCRBeamSearchClassifierCNN (const String &filename)
	Allow to implicitly load the default character classifier when creating an OCRBeamSearchDecoder object. More...
Ptr< OCRHMMDecoder::ClassifierCallback >	loadOCRHMMClassifierCNN (const String &filename)
	Allow to implicitly load the default character classifier when creating an OCRHMMDecoder object. More...
Ptr< OCRHMMDecoder::ClassifierCallback >	loadOCRHMMClassifierNM (const String &filename)
	Allow to implicitly load the default character classifier when creating an OCRHMMDecoder object. More...
void	MSERsToERStats (InputArray image, std::vector< std::vector< Point > > &contours, std::vector< std::vector< ERStat > > &regions)
	Converts MSER contours (vector<Point>) to ERStat regions. More...

Function Documentation

createOCRHMMTransitionsTable() [1/2]

void cv::text::createOCRHMMTransitionsTable	(	std::string &	vocabulary,
		std::vector< std::string > &	lexicon,
		OutputArray	transition_probabilities_table
	)

Utility function to create a tailored language model transitions table from a given list of words (lexicon).

Parameters

vocabulary	The language vocabulary (chars when ascii english text).
lexicon	The list of words that are expected to be found in a particular image.
transition_probabilities_table	Output table with transition probabilities between character pairs. cols == rows == vocabulary.size().

The function calculate frequency statistics of character pairs from the given lexicon and fills the output transition_probabilities_table with them. The transition_probabilities_table can be used as input in the OCRHMMDecoder::create() and OCRBeamSearchDecoder::create() methods.

Note

• (C++) An alternative would be to load the default generic language transition table provided in the text module samples folder (created from ispell 42869 english words list) : https://github.com/opencv/opencv_contrib/blob/master/modules/text/samples/OCRHMM_transitions_table.xml

createOCRHMMTransitionsTable() [2/2]

Mat cv::text::createOCRHMMTransitionsTable	(	const String &	vocabulary,
		std::vector< cv::String > &	lexicon
	)

loadOCRBeamSearchClassifierCNN()

Ptr<OCRBeamSearchDecoder::ClassifierCallback> cv::text::loadOCRBeamSearchClassifierCNN

(

const String &

filename

)

Allow to implicitly load the default character classifier when creating an OCRBeamSearchDecoder object.

Parameters

filename

The XML or YAML file with the classifier model (e.g. OCRBeamSearch_CNN_model_data.xml.gz)

The CNN default classifier is based in the scene text recognition method proposed by Adam Coates & Andrew NG in [Coates11a]. The character classifier consists in a Single Layer Convolutional Neural Network and a linear classifier. It is applied to the input image in a sliding window fashion, providing a set of recognitions at each window location.