altorenderer.cpp

// File:        altorenderer.cpp
// Description: ALTO rendering interface
// Author:      Jake Sebright

// (C) Copyright 2018
// 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 "errcode.h" // for ASSERT_HOST
#include "helpers.h" // for copy_string
#include "tprintf.h" // for tprintf

#include <tesseract/baseapi.h>
#include <tesseract/renderer.h>

#include <memory>
#include <sstream> // for std::stringstream

namespace tesseract {

/// Add coordinates to specified TextBlock, TextLine or String bounding box.
/// Add word confidence if adding to a String bounding box.
///
static void AddBoxToAlto(const ResultIterator *it, PageIteratorLevel level,
                         std::stringstream &alto_str) {
  int left, top, right, bottom;
  it->BoundingBox(level, &left, &top, &right, &bottom);

  int hpos = left;
  int vpos = top;
  int height = bottom - top;
  int width = right - left;

  alto_str << " HPOS=\"" << hpos << "\"";
  alto_str << " VPOS=\"" << vpos << "\"";
  alto_str << " WIDTH=\"" << width << "\"";
  alto_str << " HEIGHT=\"" << height << "\"";

  if (level == RIL_WORD) {
    int wc = it->Confidence(RIL_WORD);
    alto_str << " WC=\"0." << wc << "\"";
  } else {
    alto_str << ">";
  }
}

static std::string GetID(char const * prefix, int page_number, int counter) {
  std::stringstream idstr;
  // IDs will only have the counter for the first page to keep them consistent
  // with the IDs assigned before this change was made.
  // From the second page on, IDs will also contain the page number to make them unique.
  if (page_number == 0) {
    idstr << prefix << "_" << counter;
  } else {
    idstr << prefix << "_" << page_number << "_" << counter;
  }

  return idstr.str();
}

///
/// Append the ALTO XML for the beginning of the document
///
bool TessAltoRenderer::BeginDocumentHandler() {
  // Delay the XML output because we need the name of the image file.
  begin_document = true;
  return true;
}

///
/// Append the ALTO XML for the layout of the image
///
bool TessAltoRenderer::AddImageHandler(TessBaseAPI *api) {
  if (begin_document) {
    AppendString(
      "<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n"
      "<alto xmlns=\"http://www.loc.gov/standards/alto/ns-v3#\" "
      "xmlns:xsi=\"http://www.w3.org/2001/XMLSchema-instance\" "
      "xsi:schemaLocation=\"http://www.loc.gov/standards/alto/ns-v3# "
      "http://www.loc.gov/alto/v3/alto-3-0.xsd\">\n"
      "\t<Description>\n"
      "\t\t<MeasurementUnit>pixel</MeasurementUnit>\n"
      "\t\t<sourceImageInformation>\n"
      "\t\t\t<fileName>");

    AppendString(api->GetInputName());

    AppendString(
      "</fileName>\n"
      "\t\t</sourceImageInformation>\n"
      "\t\t<OCRProcessing ID=\"OCR_0\">\n"
      "\t\t\t<ocrProcessingStep>\n"
      "\t\t\t\t<processingSoftware>\n"
      "\t\t\t\t\t<softwareName>tesseract ");
    AppendString(TessBaseAPI::Version());
    AppendString(
      "</softwareName>\n"
      "\t\t\t\t</processingSoftware>\n"
      "\t\t\t</ocrProcessingStep>\n"
      "\t\t</OCRProcessing>\n"
      "\t</Description>\n"
      "\t<Layout>\n");
    begin_document = false;
  }

  const std::unique_ptr<const char[]> text(api->GetAltoText(imagenum()));
  if (text == nullptr) {
    return false;
  }

  AppendString(text.get());

  return true;
}

///
/// Append the ALTO XML for the end of the document
///
bool TessAltoRenderer::EndDocumentHandler() {
  AppendString("\t</Layout>\n</alto>\n");

  return true;
}

TessAltoRenderer::TessAltoRenderer(const char *outputbase)
    : TessResultRenderer(outputbase, "xml"),
      begin_document(false) {}

///
/// Make an XML-formatted string with ALTO markup from the internal
/// data structures.
///
char *TessBaseAPI::GetAltoText(int page_number) {
  return GetAltoText(nullptr, page_number);
}

///
/// Make an XML-formatted string with ALTO markup from the internal
/// data structures.
///
char *TessBaseAPI::GetAltoText(ETEXT_DESC *monitor, int page_number) {
  if (tesseract_ == nullptr || (page_res_ == nullptr && Recognize(monitor) < 0)) {
    return nullptr;
  }

  int lcnt = 0, tcnt = 0, bcnt = 0, wcnt = 0;

  if (input_file_.empty()) {
    SetInputName(nullptr);
  }

  std::stringstream alto_str;
  // Use "C" locale (needed for int values larger than 999).
  alto_str.imbue(std::locale::classic());
  alto_str << "\t\t<Page WIDTH=\"" << rect_width_ << "\" HEIGHT=\"" << rect_height_
           << "\" PHYSICAL_IMG_NR=\"" << page_number << "\""
           << " ID=\"page_" << page_number << "\">\n"
           << "\t\t\t<PrintSpace HPOS=\"0\" VPOS=\"0\""
           << " WIDTH=\"" << rect_width_ << "\""
           << " HEIGHT=\"" << rect_height_ << "\">\n";

  std::unique_ptr<ResultIterator> res_it(GetIterator());
  while (!res_it->Empty(RIL_BLOCK)) {
    if (res_it->Empty(RIL_WORD)) {
      res_it->Next(RIL_WORD);
      continue;
    }

    int left, top, right, bottom;
    auto block_type = res_it->BlockType();

    switch (block_type) {
      case PT_FLOWING_IMAGE:
      case PT_HEADING_IMAGE:
      case PT_PULLOUT_IMAGE: {
        // Handle all kinds of images.
        // TODO: optionally add TYPE, for example TYPE="photo".
        alto_str << "\t\t\t\t<Illustration ID=\"" << GetID("cblock", page_number, bcnt++) << "\"";
        AddBoxToAlto(res_it.get(), RIL_BLOCK, alto_str);
        alto_str << "</Illustration>\n";
        res_it->Next(RIL_BLOCK);
        continue;
      }
      case PT_HORZ_LINE:
      case PT_VERT_LINE:
        // Handle horizontal and vertical lines.
        alto_str << "\t\t\t\t<GraphicalElement ID=\"" << GetID("cblock", page_number, bcnt++) << "\"";
        AddBoxToAlto(res_it.get(), RIL_BLOCK, alto_str);
        alto_str << "</GraphicalElement >\n";
        res_it->Next(RIL_BLOCK);
        continue;
      case PT_NOISE:
        tprintf("TODO: Please report image which triggers the noise case.\n");
        ASSERT_HOST(false);
      default:
        break;
    }

    if (res_it->IsAtBeginningOf(RIL_BLOCK)) {
      alto_str << "\t\t\t\t<ComposedBlock ID=\"" << GetID("cblock", page_number, bcnt) << "\"";
      AddBoxToAlto(res_it.get(), RIL_BLOCK, alto_str);
      alto_str << "\n";
    }

    if (res_it->IsAtBeginningOf(RIL_PARA)) {
      alto_str << "\t\t\t\t\t<TextBlock ID=\"" << GetID("block", page_number, tcnt) << "\"";
      AddBoxToAlto(res_it.get(), RIL_PARA, alto_str);
      alto_str << "\n";
    }

    if (res_it->IsAtBeginningOf(RIL_TEXTLINE)) {
      alto_str << "\t\t\t\t\t\t<TextLine ID=\"" << GetID("line", page_number, lcnt) << "\"";
      AddBoxToAlto(res_it.get(), RIL_TEXTLINE, alto_str);
      alto_str << "\n";
    }

    alto_str << "\t\t\t\t\t\t\t<String ID=\"" << GetID("string", page_number, wcnt) << "\"";
    AddBoxToAlto(res_it.get(), RIL_WORD, alto_str);
    alto_str << " CONTENT=\"";

    bool last_word_in_line = res_it->IsAtFinalElement(RIL_TEXTLINE, RIL_WORD);
    bool last_word_in_tblock = res_it->IsAtFinalElement(RIL_PARA, RIL_WORD);
    bool last_word_in_cblock = res_it->IsAtFinalElement(RIL_BLOCK, RIL_WORD);

    res_it->BoundingBox(RIL_WORD, &left, &top, &right, &bottom);

    do {
      const std::unique_ptr<const char[]> grapheme(res_it->GetUTF8Text(RIL_SYMBOL));
      if (grapheme && grapheme[0] != 0) {
        alto_str << HOcrEscape(grapheme.get()).c_str();
      }
      res_it->Next(RIL_SYMBOL);
    } while (!res_it->Empty(RIL_BLOCK) && !res_it->IsAtBeginningOf(RIL_WORD));

    alto_str << "\"/>";

    wcnt++;

    if (last_word_in_line) {
      alto_str << "\n\t\t\t\t\t\t</TextLine>\n";
      lcnt++;
    } else {
      int hpos = right;
      int vpos = top;
      res_it->BoundingBox(RIL_WORD, &left, &top, &right, &bottom);
      int width = left - hpos;
      alto_str << "<SP WIDTH=\"" << width << "\" VPOS=\"" << vpos << "\" HPOS=\"" << hpos
               << "\"/>\n";
    }

    if (last_word_in_tblock) {
      alto_str << "\t\t\t\t\t</TextBlock>\n";
      tcnt++;
    }

    if (last_word_in_cblock) {
      alto_str << "\t\t\t\t</ComposedBlock>\n";
      bcnt++;
    }
  }

  alto_str << "\t\t\t</PrintSpace>\n"
           << "\t\t</Page>\n";

  return copy_string(alto_str.str());
}

} // namespace tesseract