tesseract/api/baseapi.h

///////////////////////////////////////////////////////////////////////
// File:        baseapi.h
// Description: Simple API for calling tesseract.
// Author:      Ray Smith
// Created:     Fri Oct 06 15:35:01 PDT 2006
//
// (C) Copyright 2006, Google Inc.
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
// http://www.apache.org/licenses/LICENSE-2.0
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
///////////////////////////////////////////////////////////////////////

#ifndef TESSERACT_CCMAIN_BASEAPI_H__
#define TESSERACT_CCMAIN_BASEAPI_H__

#include "thresholder.h"

class PAGE_RES;
class PAGE_RES_IT;
class BLOCK_LIST;
class IMAGE;
class STRING;
struct Pix;
struct Box;
struct Pixa;
struct Boxa;
struct ETEXT_STRUCT;
struct OSResults;
struct TBOX;

#define MAX_NUM_INT_FEATURES 512
struct INT_FEATURE_STRUCT;
typedef INT_FEATURE_STRUCT *INT_FEATURE;
typedef INT_FEATURE_STRUCT INT_FEATURE_ARRAY[MAX_NUM_INT_FEATURES];

#ifdef TESSDLL_EXPORTS
#define TESSDLL_API __declspec(dllexport)
#elif defined(TESSDLL_IMPORTS)
#define TESSDLL_API __declspec(dllimport)
#else
#define TESSDLL_API
#endif


namespace tesseract {

class Dict;
class Tesseract;
class Trie;
class CubeRecoContext;
class TesseractCubeCombiner;
class CubeObject;
class CubeLineObject;
class Dawg;

typedef int (Dict::*DictFunc)(void* void_dawg_args, int char_index,
                              const void *word, bool word_end);

enum PageSegMode {
  PSM_AUTO,           ///< Fully automatic page segmentation.
  PSM_SINGLE_COLUMN,  ///< Assume a single column of text of variable sizes.
  PSM_SINGLE_BLOCK,   ///< Assume a single uniform block of text. (Default.)
  PSM_SINGLE_LINE,    ///< Treat the image as a single text line.
  PSM_SINGLE_WORD,    ///< Treat the image as a single word.
  PSM_SINGLE_CHAR,    ///< Treat the image as a single character.

  PSM_COUNT           ///< Number of enum entries.
};

/**
 * The values in the AccuracyVSpeed enum provide hints for how the engine
 * should trade speed for accuracy. There is no guarantee of any effect.
 */
enum AccuracyVSpeed {
  AVS_FASTEST = 0,         ///< Fastest speed, but lowest accuracy.
  AVS_MOST_ACCURATE = 100  ///< Greatest accuracy, but slowest speed.
};

/**
 * Base class for all tesseract APIs.
 * Specific classes can add ability to work on different inputs or produce
 * different outputs.
 * This class is mostly an interface layer on top of the Tesseract instance
 * class to hide the data types so that users of this class don't have to
 * include any other Tesseract headers.
 */
class TESSDLL_API TessBaseAPI {
 public:
  TessBaseAPI();
  virtual ~TessBaseAPI();

  /**
   * Set the name of the input file. Needed only for training and
   * reading a UNLV zone file.
   */
  void SetInputName(const char* name);

  /** Set the name of the bonus output files. Needed only for debugging. */
  void SetOutputName(const char* name);

  /**
   * Set the value of an internal "variable" (of either old or new types).
   * Supply the name of the variable and the value as a string, just as
   * you would in a config file.
   * Returns false if the name lookup failed.
   * Eg SetVariable("tessedit_char_blacklist", "xyz"); to ignore x, y and z.
   * Or SetVariable("bln_numericmode", "1"); to set numeric-only mode.
   * SetVariable may be used before Init, but settings will revert to
   * defaults on End().
   */
  bool SetVariable(const char* variable, const char* value);

  /**
   * Eventually instances will be thread-safe and totally independent,
   * but for now, they all point to the same underlying engine,
   * and are NOT RE-ENTRANT OR THREAD-SAFE. For now:
   * it is safe to Init multiple TessBaseAPIs in the same language, use them
   * sequentially, and End or delete them all, but once one is Ended, you can't
   * do anything other than End the others. After End, it is safe to Init
   * again on the same one.
   *
   * Start tesseract. Returns zero on success and -1 on failure.
   * NOTE that the only members that may be called before Init are those
   * listed above here in the class definition.
   *
   * The datapath must be the name of the data directory (no ending /) or
   * some other file in which the data directory resides (for instance argv[0].)
   * The language is (usually) an ISO 639-3 string or NULL will default to eng.
   * It is entirely safe (and eventually will be efficient too) to call
   * Init multiple times on the same instance to change language, or just
   * to reset the classifier.
   * WARNING: On changing languages, all Variables are reset back to their
   * default values. If you have a rare need to set a Variable that controls
   * initialization for a second call to Init you should explicitly
   * call End() and then use SetVariable before Init. This is only a very
   * rare use case, since there are very few uses that require any variables
   * to be set before Init.
   */
  int Init(const char* datapath, const char* language,
           char **configs, int configs_size, bool configs_global_only);
  int Init(const char* datapath, const char* language) {
    return Init(datapath, language, 0, 0, false);
  }

  /**
   * Init only the lang model component of Tesseract. The only functions
   * that work after this init are SetVariable and IsValidWord.
   * WARNING: temporary! This function will be removed from here and placed
   * in a separate API at some future time.
   */
  int InitLangMod(const char* datapath, const char* language);

  /**
   * Init everything except the language model. Used to allow initialization for
   * the specified language without any available dawg models.
   */
  int InitWithoutLangModel(const char* datapath, const char* language);

  /**
   * Read a "config" file containing a set of variable, value pairs.
   * Searches the standard places: tessdata/configs, tessdata/tessconfigs
   * and also accepts a relative or absolute path name.
   */
  void ReadConfigFile(const char* filename, bool global_only);

  /**
   * Set the current page segmentation mode. Defaults to PSM_SINGLE_BLOCK.
   * The mode is stored as an INT_VARIABLE so it can also be modified by
   * ReadConfigFile or SetVariable("tessedit_pageseg_mode", mode as string).
   */
  void SetPageSegMode(PageSegMode mode);

  /** Return the current page segmentation mode. */
  PageSegMode GetPageSegMode() const;

  /**
   * Set the hint for trading accuracy against speed.
   * Default is AVS_FASTEST, which is the old behaviour.
   * Note that this is only a hint. Depending on the language and/or
   * build configuration, speed and accuracy may not be tradeable.
   * Also note that despite being an enum, any value in the range
   * AVS_FASTEST to AVS_MOST_ACCURATE can be provided, and may or may not
   * have an effect, depending on the implementation.
   * The mode is stored as an INT_VARIABLE so it can also be modified by
   * ReadConfigFile or SetVariable("tessedit_accuracyvspeed", mode as string).
   */
  void SetAccuracyVSpeed(AccuracyVSpeed mode);

  /**
   * Recognize a rectangle from an image and return the result as a string.
   * May be called many times for a single Init.
   * Currently has no error checking.
   * Greyscale of 8 and color of 24 or 32 bits per pixel may be given.
   * Palette color images will not work properly and must be converted to
   * 24 bit.
   * Binary images of 1 bit per pixel may also be given but they must be
   * byte packed with the MSB of the first byte being the first pixel, and a
   * 1 represents WHITE. For binary images set bytes_per_pixel=0.
   * The recognized text is returned as a char* which is coded
   * as UTF8 and must be freed with the delete [] operator.
   *
   * Note that TesseractRect is the simplified convenience interface.
   * For advanced uses, use SetImage, (optionally) SetRectangle, Recognize,
   * and one or more of the Get*Text functions below.
   */
  char* TesseractRect(const unsigned char* imagedata,
                      int bytes_per_pixel, int bytes_per_line,
                      int left, int top, int width, int height);

  /**
   * Call between pages or documents etc to free up memory and forget
   * adaptive data.
   */
  void ClearAdaptiveClassifier();

  /**
   * @defgroup AdvancedAPI Advanced API
   * The following methods break TesseractRect into pieces, so you can
   * get hold of the thresholded image, get the text in different formats,
   * get bounding boxes, confidences etc.
   */
   /* @{ */

  /**
   * Provide an image for Tesseract to recognize. Format is as
   * TesseractRect above. Does not copy the image buffer, or take
   * ownership. The source image may be destroyed after Recognize is called,
   * either explicitly or implicitly via one of the Get*Text functions.
   * SetImage clears all recognition results, and sets the rectangle to the
   * full image, so it may be followed immediately by a GetUTF8Text, and it
   * will automatically perform recognition.
   */
  void SetImage(const unsigned char* imagedata, int width, int height,
                int bytes_per_pixel, int bytes_per_line);

  /**
   * Provide an image for Tesseract to recognize. As with SetImage above,
   * Tesseract doesn't take a copy or ownership or pixDestroy the image, so
   * it must persist until after Recognize.
   * Pix vs raw, which to use?
   * Use Pix where possible. A future version of Tesseract may choose to use Pix
   * as its internal representation and discard IMAGE altogether.
   * Because of that, an implementation that sources and targets Pix may end up
   * with less copies than an implementation that does not.
   */
  void SetImage(const Pix* pix);

  /**
   * Restrict recognition to a sub-rectangle of the image. Call after SetImage.
   * Each SetRectangle clears the recogntion results so multiple rectangles
   * can be recognized with the same image.
   */
  void SetRectangle(int left, int top, int width, int height);

  /**
   * In extreme cases only, usually with a subclass of Thresholder, it
   * is possible to provide a different Thresholder. The Thresholder may
   * be preloaded with an image, settings etc, or they may be set after.
   * Note that Tesseract takes ownership of the Thresholder and will
   * delete it when it it is replaced or the API is destructed.
   */
  void SetThresholder(ImageThresholder* thresholder) {
    if (thresholder_ != 0)
      delete thresholder_;
    thresholder_ = thresholder;
    ClearResults();
  }

  /**
   * Get a copy of the internal thresholded image from Tesseract.
   * Caller takes ownership of the Pix and must pixDestroy it.
   * May be called any time after SetImage, or after TesseractRect.
   */
  Pix* GetThresholdedImage();

  /**
   * Get the result of page layout analysis as a leptonica-style
   * Boxa, Pixa pair, in reading order.
   * Can be called before or after Recognize.
   */
  Boxa* GetRegions(Pixa** pixa);

  /**
   * Get the textlines as a leptonica-style
   * Boxa, Pixa pair, in reading order.
   * Can be called before or after Recognize.
   * If blockids is not NULL, the block-id of each line is also returned as an
   * array of one element per line. delete [] after use.
   */
  Boxa* GetTextlines(Pixa** pixa, int** blockids);

  /**
   * Get the words as a leptonica-style
   * Boxa, Pixa pair, in reading order.
   * Can be called before or after Recognize.
   */
  Boxa* GetWords(Pixa** pixa);

  /**
   * Dump the internal binary image to a PGM file.
   * @deprecated Use GetThresholdedImage and write the image using pixWrite
   * instead if possible.
   */
  void DumpPGM(const char* filename);

  /**
   * Recognize the image from SetAndThresholdImage, generating Tesseract
   * internal structures. Returns 0 on success.
   * Optional. The Get*Text functions below will call Recognize if needed.
   * After Recognize, the output is kept internally until the next SetImage.
   */
  int Recognize(ETEXT_STRUCT* monitor);

  /**
   * Methods to retrieve information after SetAndThresholdImage(),
   * Recognize() or TesseractRect(). (Recognize is called implicitly if needed.)
   */

  /** Variant on Recognize used for testing chopper. */
  int RecognizeForChopTest(struct ETEXT_STRUCT* monitor);

  /**
   * The recognized text is returned as a char* which is coded
   * as UTF8 and must be freed with the delete [] operator.
   */
  char* GetUTF8Text();
  /**
   * Make a HTML-formatted string with hOCR markup from the internal
   * data structures.
   * STL removed from original patch submission and refactored by rays.
   * page_id is 1-based and will appear in the output.
   */
 char* GetHOCRText(int page_id);
  /**
   * The recognized text is returned as a char* which is coded in the same
   * format as a box file used in training. Returned string must be freed with
   * the delete [] operator.
   * Constructs coordinates in the original image - not just the rectangle.
   * page_number is a 0-base page index that will appear in the box file.
   */
  char* GetBoxText(int page_number);
  /**
   * The recognized text is returned as a char* which is coded
   * as UNLV format Latin-1 with specific reject and suspect codes
   * and must be freed with the delete [] operator.
   */
  char* GetUNLVText();
  /** Returns the (average) confidence value between 0 and 100. */
  int MeanTextConf();
  /**
   * Returns all word confidences (between 0 and 100) in an array, terminated
   * by -1.  The calling function must delete [] after use.
   * The number of confidences should correspond to the number of space-
   * delimited words in GetUTF8Text.
   */
  int* AllWordConfidences();

  /**
   * Free up recognition results and any stored image data, without actually
   * freeing any recognition data that would be time-consuming to reload.
   * Afterwards, you must call SetImage or TesseractRect before doing
   * any Recognize or Get* operation.
   */
  void Clear();

  /**
   * Close down tesseract and free up all memory. End() is equivalent to
   * destructing and reconstructing your TessBaseAPI.
   * Once End() has been used, none of the other API functions may be used
   * other than Init and anything declared above it in the class definition.
   */
  void End();

  /**
   * Check whether a word is valid according to Tesseract's language model
   * @return 0 if the word is invalid, non-zero if valid.
   * @warning temporary! This function will be removed from here and placed
   * in a separate API at some future time.
   */
  int IsValidWord(const char *word);

  bool GetTextDirection(int* out_offset, float* out_slope);

  /** Set the letter_is_okay function to point somewhere else. */
  void SetDictFunc(DictFunc f);

  /**
   * Estimates the Orientation And Script of the image.
   * @return true if the image was processed successfully.
   */
  bool DetectOS(OSResults*);

  /** This method returns the features associated with the input image. */
  void GetFeatures(INT_FEATURE_ARRAY int_features,
                   int* num_features);

  /** Return the pointer to the i-th dawg loaded into tesseract_ object. */
  const Dawg *GetDawg(int i) const;

  /** Return the number of dawgs loaded into tesseract_ object. */
  int NumDawgs() const;

  /** Return the language used in the last valid initialization. */
  const char* GetLastInitLanguage() const;

 /* @} */

 protected:

  /** Common code for setting the image. Returns true if Init has been called. */
  bool InternalSetImage();

  /**
   * Run the thresholder to make the thresholded image. If pix is not NULL,
   * the source is thresholded to pix instead of the internal IMAGE.
   */
  virtual void Threshold(Pix** pix);

  /**
   * Find lines from the image making the BLOCK_LIST.
   * @return 0 on success.
   */
  int FindLines();

  /** Delete the pageres and block list ready for a new page. */
  void ClearResults();

  /**
   * Return the length of the output text string, as UTF8, assuming
   * one newline per line and one per block, with a terminator,
   * and assuming a single character reject marker for each rejected character.
   * Also return the number of recognized blobs in blob_count.
   */
  int TextLength(int* blob_count);

  /** @defgroup ocropusAddOns ocropus add-ons */

  /* @{ */
  /** Find lines from the image making the BLOCK_LIST. */
  BLOCK_LIST* FindLinesCreateBlockList();

  /**
   * Delete a block list.
   * This is to keep BLOCK_LIST pointer opaque
   * and let go of including the other headers.
   */
  static void DeleteBlockList(BLOCK_LIST* block_list);

  /**
   * Adapt to recognize the current image as the given character.
   * The image must be preloaded and be just an image of a single character.
   */
  void AdaptToCharacter(const char *unichar_repr,
                        int length,
                        float baseline,
                        float xheight,
                        float descender,
                        float ascender);

  /** Recognize text doing one pass only, using settings for a given pass. */
  /*static*/ PAGE_RES* RecognitionPass1(BLOCK_LIST* block_list);
  /*static*/ PAGE_RES* RecognitionPass2(BLOCK_LIST* block_list,
                                    PAGE_RES* pass1_result);

  /**
   * Extract the OCR results, costs (penalty points for uncertainty),
   * and the bounding boxes of the characters.
   */
  static int TesseractExtractResult(char** text,
                                    int** lengths,
                                    float** costs,
                                    int** x0,
                                    int** y0,
                                    int** x1,
                                    int** y1,
                                    PAGE_RES* page_res);

  /**
   * Call the Cube OCR engine. Takes the Region, line and word segmentation
   * information from Tesseract as inputs. Makes changes or populates the
   * output PAGE_RES object which contains the recogntion results.
   * The behavior of this function depends on the
   * current language and the value of the tessedit_accuracyvspeed:
   * For English (and other Latin based scripts):
   *    If the accuracyvspeed flag is set to any value other than AVS_FASTEST,
   *    Cube uses the word information passed by Tesseract.
   *    Cube will run on a subset of the words segmented and recognized by
   *    Tesseract. The value of the accuracyvspeed and the Tesseract
   *    confidence of a word determines whether Cube runs on it or not and
   *    whether Cube's results override Tesseract's
   * For Arabic & Hindi:
   *    Cube uses the Region information passed by Tesseract. It then performs
   *    its own line segmentation. This will change once Tesseract's line
   *    segmentation works for Arabic. Cube then segments each line into
   *    phrases. Each phrase is then recognized in phrase mode which allows
   *    spaces in the results.
   *    Note that at this point, the line segmentation algorithm might have
   *    some problems with ill spaced Arabic document.
   */
  int Cube();
  /** Run Cube on the lines extracted by Tesseract. */
  int RunCubeOnLines();
  /**
   * Run Cube on a subset of the words already present in the page_res_ object
   * The subset, and whether Cube overrides the results is determined by
   * the SpeedVsAccuracy flag
   */
  int CubePostProcessWords();
  /** Create a Cube line object for each line */
  CubeLineObject **CreateLineObjects(Pixa* pixa_lines);
  /**
   * Create a TBox array corresponding to the phrases in the array of
   * line objects
   */
  TBOX *CreatePhraseBoxes(Boxa* boxa_lines, CubeLineObject **line_objs,
                          int *phrase_cnt);
  /** Recognize the phrases saving the results to the page_res_ object */
  bool RecognizePhrases(int line_cnt, int phrase_cnt,
                        CubeLineObject **line_objs, TBOX *phrase_boxes);
  /** Recognize a single phrase saving the results to the page_res_ object */
  bool RecognizePhrase(CubeObject *phrase, PAGE_RES_IT *result);
  /** Create the necessary Cube Objects */
  bool CreateCubeObjects();
  /* @} */

 protected:
   Tesseract*        tesseract_;       ///< The underlying data object.
   ImageThresholder* thresholder_;     ///< Image thresholding module.
   bool              threshold_done_;  ///< Image has been passed to page_image.
   BLOCK_LIST*       block_list_;      ///< The page layout.
   PAGE_RES*         page_res_;        ///< The page-level data.
   STRING*           input_file_;      ///< Name used by training code.
   STRING*           output_file_;     ///< Name used by debug code.
   STRING*           datapath_;        ///< Current location of tessdata.
   STRING*           language_;        ///< Last initialized language.

  /** 
   * @defgroup ThresholderParams 
   * Parameters saved from the Thresholder. Needed to rebuild coordinates.
   */
  /* @{ */
  int rect_left_;
  int rect_top_;
  int rect_width_;
  int rect_height_;
  int image_width_;
  int image_height_;
  /* @} */
};

} // namespace tesseract.

#endif // TESSERACT_CCMAIN_BASEAPI_H__