tesseract/training/normstrngs.cpp

/**********************************************************************
 * File:        normstrngs.cpp
 * Description: Utilities to normalize and manipulate UTF-32 and
 *              UTF-8 strings.
 * Author:      Ranjith Unnikrishnan
 * Created:     Thu July 4 2013
 *
 * (C) Copyright 2013, 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.
 *
 **********************************************************************/

#include "normstrngs.h"

#include "icuerrorcode.h"
#include "unichar.h"
#include "unicode/normalizer2.h"  // From libicu
#include "unicode/translit.h"     // From libicu
#include "unicode/unorm2.h"       // From libicu

namespace tesseract {

void UTF8ToUTF32(const char* utf8_str, GenericVector<char32>* str32) {
  str32->clear();
  str32->reserve(strlen(utf8_str));
  int len = strlen(utf8_str);
  int step = 0;
  for (int ch = 0; ch < len; ch += step) {
    step = UNICHAR::utf8_step(utf8_str + ch);
    if (step > 0) {
      UNICHAR uni_ch(utf8_str + ch, step);
      (*str32) += uni_ch.first_uni();
    }
  }
}

void UTF32ToUTF8(const GenericVector<char32>& str32, STRING* utf8_str) {
  utf8_str->ensure(str32.length());
  utf8_str->assign("", 0);
  for (int i = 0; i < str32.length(); ++i) {
    UNICHAR uni_ch(str32[i]);
    char *utf8 = uni_ch.utf8_str();
    if (utf8 != NULL) {
      (*utf8_str) += utf8;
      delete[] utf8;
    }
  }
}

bool is_hyphen_punc(const char32 ch) {
  static const int kNumHyphenPuncUnicodes = 13;
  static const char32 kHyphenPuncUnicodes[kNumHyphenPuncUnicodes] = {
    '-',
    0x2010, 0x2011, 0x2012, 0x2013, 0x2014, 0x2015,  // hyphen..horizontal bar
    0x207b,  // superscript minus
    0x208b,  // subscript minus
    0x2212,  // minus sign
    0xfe58,  // small em dash
    0xfe63,  // small hyphen-minus
    0xff0d,  // fullwidth hyphen-minus
  };
  for (int i = 0; i < kNumHyphenPuncUnicodes; ++i) {
    if (kHyphenPuncUnicodes[i] == ch)
      return true;
  }
  return false;
}

bool is_single_quote(const char32 ch) {
  static const int kNumSingleQuoteUnicodes = 8;
  static const char32 kSingleQuoteUnicodes[kNumSingleQuoteUnicodes] = {
    '\'',
    '`',
    0x2018,  // left single quotation mark (English, others)
    0x2019,  // right single quotation mark (Danish, Finnish, Swedish, Norw.)
             // We may have to introduce a comma set with 0x201a
    0x201B,  // single high-reveresed-9 quotation mark (PropList.txt)
    0x2032,  // prime
    0x300C,  // left corner bracket (East Asian languages)
    0xFF07,  // fullwidth apostrophe
  };
  for (int i = 0; i < kNumSingleQuoteUnicodes; ++i) {
    if (kSingleQuoteUnicodes[i] == ch)
      return true;
  }
  return false;
}

bool is_double_quote(const char32 ch) {
  static const int kNumDoubleQuoteUnicodes = 8;
  static const char32 kDoubleQuoteUnicodes[kNumDoubleQuoteUnicodes] = {
    '"',
    0x201C,  // left double quotation mark (English, others)
    0x201D,  // right double quotation mark (Danish, Finnish, Swedish, Norw.)
    0x201F,  // double high-reversed-9 quotation mark (PropList.txt)
    0x2033,  // double prime
    0x301D,  // reversed double prime quotation mark (East Asian langs, horiz.)
    0x301E,  // close double prime (East Asian languages written horizontally)
    0xFF02,  // fullwidth quotation mark
  };
  for (int i = 0; i < kNumDoubleQuoteUnicodes; ++i) {
    if (kDoubleQuoteUnicodes[i] == ch)
      return true;
  }
  return false;
}

STRING NormalizeUTF8String(const char* str8) {
  GenericVector<char32> str32, out_str32, norm_str;
  UTF8ToUTF32(str8, &str32);
  for (int i = 0; i < str32.length(); ++i) {
    norm_str.clear();
    NormalizeChar32(str32[i], &norm_str);
    for (int j = 0; j < norm_str.length(); ++j) {
      out_str32.push_back(norm_str[j]);
    }
  }
  STRING out_str8;
  UTF32ToUTF8(out_str32, &out_str8);
  return out_str8;
}

void NormalizeChar32(char32 ch, GenericVector<char32>* str) {
  IcuErrorCode error_code;
  const icu::Normalizer2* nfkc = icu::Normalizer2::getInstance(
      NULL, "nfkc", UNORM2_COMPOSE, error_code);
  error_code.assertSuccess();
  error_code.reset();

  icu::UnicodeString uch_str(static_cast<UChar32>(ch));
  icu::UnicodeString norm_str = nfkc->normalize(uch_str, error_code);
  error_code.assertSuccess();

  str->clear();
  for (int i = 0; i < norm_str.length(); ++i) {
    // If any spaces were added by NFKC, pretend normalization is a nop.
    if (norm_str[i] == ' ') {
      str->clear();
      str->push_back(ch);
      break;
    } else {
      str->push_back(OCRNormalize(static_cast<char32>(norm_str[i])));
    }
  }
}

// Apply just the OCR-specific normalizations and return the normalized char.
char32 OCRNormalize(char32 ch) {
  if (is_hyphen_punc(ch))
    return '-';
  else if (is_single_quote(ch))
    return '\'';
  else if (is_double_quote(ch))
    return '"';
  return ch;
}

bool IsOCREquivalent(char32 ch1, char32 ch2) {
  return OCRNormalize(ch1) == OCRNormalize(ch2);
}

bool IsValidCodepoint(const char32 ch) {
  // In the range [0, 0xD800) or [0xE000, 0x10FFFF]
  return (static_cast<uinT32>(ch) < 0xD800)
      || (ch >= 0xE000 && ch <= 0x10FFFF);
}

bool IsWhitespace(const char32 ch) {
  ASSERT_HOST_MSG(IsValidCodepoint(ch),
                  "Invalid Unicode codepoint: 0x%x\n", ch);
  return u_isUWhiteSpace(static_cast<UChar32>(ch));
}

bool IsUTF8Whitespace(const char* text) {
  return SpanUTF8Whitespace(text) == strlen(text);
}

int SpanUTF8Whitespace(const char* text) {
  int n_white = 0;
  for (UNICHAR::const_iterator it = UNICHAR::begin(text, strlen(text));
       it != UNICHAR::end(text, strlen(text));
       ++it) {
    if (!IsWhitespace(*it)) break;
    n_white += it.utf8_len();
  }
  return n_white;
}

int SpanUTF8NotWhitespace(const char* text) {
  int n_notwhite = 0;
  for (UNICHAR::const_iterator it = UNICHAR::begin(text, strlen(text));
       it != UNICHAR::end(text, strlen(text));
       ++it) {
    if (IsWhitespace(*it)) break;
    n_notwhite += it.utf8_len();
  }
  return n_notwhite;
}

bool IsInterchangeValid(const char32 ch) {
  return IsValidCodepoint(ch) &&
      !(ch >= 0xFDD0 && ch <= 0xFDEF) &&  // Noncharacters.
      !(ch >= 0xFFFE && ch <= 0xFFFF) &&
      !(ch >= 0x1FFFE && ch <= 0x1FFFF) &&
      !(ch >= 0x2FFFE && ch <= 0x2FFFF) &&
      !(ch >= 0x3FFFE && ch <= 0x3FFFF) &&
      !(ch >= 0x4FFFE && ch <= 0x4FFFF) &&
      !(ch >= 0x5FFFE && ch <= 0x5FFFF) &&
      !(ch >= 0x6FFFE && ch <= 0x6FFFF) &&
      !(ch >= 0x7FFFE && ch <= 0x7FFFF) &&
      !(ch >= 0x8FFFE && ch <= 0x8FFFF) &&
      !(ch >= 0x9FFFE && ch <= 0x9FFFF) &&
      !(ch >= 0xAFFFE && ch <= 0xAFFFF) &&
      !(ch >= 0xBFFFE && ch <= 0xBFFFF) &&
      !(ch >= 0xCFFFE && ch <= 0xCFFFF) &&
      !(ch >= 0xDFFFE && ch <= 0xDFFFF) &&
      !(ch >= 0xEFFFE && ch <= 0xEFFFF) &&
      !(ch >= 0xFFFFE && ch <= 0xFFFFF) &&
      !(ch >= 0x10FFFE && ch <= 0x10FFFF) &&
      (!u_isISOControl(static_cast<UChar32>(ch)) ||
       ch == '\n' || ch == '\f' || ch == '\t' || ch == '\r');
}

bool IsInterchangeValid7BitAscii(const char32 ch) {
  return IsValidCodepoint(ch) &&
      ch <= 128 &&
      (!u_isISOControl(static_cast<UChar32>(ch)) ||
       ch == '\n' || ch == '\f' || ch == '\t' || ch == '\r');
}

char32 FullwidthToHalfwidth(const char32 ch) {
  // Return unchanged if not in the fullwidth-halfwidth Unicode block.
  if (ch < 0xFF00 || ch > 0xFFEF || !IsValidCodepoint(ch)) {
    if (ch != 0x3000) return ch;
  }
  // Special case for fullwidth left and right "white parentheses".
  if (ch == 0xFF5F) return 0x2985;
  if (ch == 0xFF60) return 0x2986;
  // Construct a full-to-half width transliterator.
  IcuErrorCode error_code;
  icu::UnicodeString uch_str(static_cast<UChar32>(ch));
  const icu::Transliterator* fulltohalf = icu::Transliterator::createInstance(
      "Fullwidth-Halfwidth", UTRANS_FORWARD, error_code);
  error_code.assertSuccess();
  error_code.reset();

  fulltohalf->transliterate(uch_str);
  delete fulltohalf;
  ASSERT_HOST(uch_str.length() != 0);
  return uch_str[0];
}

}  // namespace tesseract