Crear su propio extractor de texto ( obsoleto )

Para crear su propio text extractor debe crear una nueva clase que extienda la interfaz AbstractTextExtractor:

package org.apache.jackrabbit.extractor;

/**
 * Base class for text extractor implementations.
 */
public abstract class AbstractTextExtractor implements TextExtractor {

    /**
     * The supported content types by this text extractor.
     */
    private final String[] contentTypes;

    /**
     * @param contentTypes the supported content types by this text extractor.
     */
    public AbstractTextExtractor(String[] contentTypes) {
        this.contentTypes = new String[contentTypes.length];
        System.arraycopy(contentTypes, 0, this.contentTypes, 0, contentTypes.length);
    }

    /**
     * @inheritDoc
     */
    public String[] getContentTypes() {
        return contentTypes;
    }
}

Ejemplo de clase:

public class SomeNameExtractor extends AbstractTextExtractor {
  public Reader extractText(InputStream stream, String type, String encoding) throws IOException
}

Internamente, TextExtractorWork llamará al método extractText como se ha mostrado anteriormente. AbstractTextExtractor es la clase base para las implementaciones de text extractor, que implementa la interfaz TextExtractor:

import java.io.IOException;
import java.io.InputStream;
import java.io.Reader;

/**
 * Interface for extracting text content from binary streams.
 */
public interface TextExtractor {
    String[] getContentTypes();
    Reader extractText(InputStream stream, String type, String encoding) throws IOException;
}

public class Tesseract3TextExtractor extends AbstractTextExtractor {
  public Reader extractText(InputStream stream, String type, String encoding) throws IOException
}

Le sugerimos crear la nueva clase dentro del paquete com.openkm.extractor.

Descripción de los métodos

Método	Tipo	Descripción
getContentTypes()	String[]	Devuelve los tipos MIME admitidos por este extractor. Las cadenas devueltas deben estar en minúsculas y el array devuelto no debe estar vacío.
extractText(InputStream stream, String type, String encoding)	String	Devuelve un lector para el contenido de texto del documento binario indicado. El tipo de contenido y la codificación de caracteres (si están disponibles y son aplicables) se pasan como argumentos.

Ejemplo de implementación del extractor de texto

/**
 * OpenKM, Open Document Management System (http://www.openkm.com)
 * Copyright (c) 2006-2015 Paco Avila & Josep Llort
 *
 * No bytes were intentionally harmed during the development of this application.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */

package com.openkm.extractor;

import com.openkm.core.Config;
import com.openkm.core.DatabaseException;
import com.openkm.util.*;
import org.apache.commons.io.IOUtils;
import org.apache.jackrabbit.extractor.AbstractTextExtractor;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.*;
import java.util.HashMap;

/**
 * Text extractor for image documents.
 * Use OCR from http://code.google.com/p/tesseract-ocr/
 */
public class Tesseract3TextExtractor extends AbstractTextExtractor {

  /**
   * Logger instance.
   */
  private static final Logger log = LoggerFactory.getLogger(Tesseract3TextExtractor.class);

  /**
   * Creates a new <code>TextExtractor</code> instance.
   */
  public Tesseract3TextExtractor() {
    super(new String[] { "image/tiff", "image/gif", "image/jpg", "image/jpeg", "image/png" });
  }

  // -------------------------------------------------------< TextExtractor >

  /**
   * {@inheritDoc}
   */
  public Reader extractText(InputStream stream, String type, String encoding) throws IOException {
    return extractText(Config.SYSTEM_OCR, stream, type, encoding);
  }

  /**
   * Extract text from image using Tesseract OCR
   */
  public String extractText(File input) throws IOException {
    return extractText(Config.SYSTEM_OCR, input);
  }

  /**
   * {@inheritDoc}
   */
  public Reader extractText(String ocr, InputStream stream, String type, String encoding) throws IOException {
    File tmpFileIn = null;

    try {
      // Create temp file
      tmpFileIn = FileUtils.createTempFileFromMime(type);
      FileOutputStream fos = new FileOutputStream(tmpFileIn);
      IOUtils.copy(stream, fos);
      fos.close();

      String text = extractText(ocr, tmpFileIn);
      return new StringReader(text);
    } catch (DatabaseException e) {
      log.warn("Failed to extract barcode text", e);
      throw new IOException(e.getMessage(), e);
    } finally {
      IOUtils.closeQuietly(stream);
      FileUtils.deleteQuietly(tmpFileIn);
    }
  }

  /**
   * Extract text from image using Tesseract OCR
   */
  public String extractText(String ocr, File input) throws IOException {
    if (!ocr.isEmpty()) {
      StringBuilder sb = new StringBuilder();
      String text = doOcr(ocr, input);
      sb.append(text);

      if (!Config.SYSTEM_OCR_ROTATE.isEmpty()) {
        String[] angles = Config.SYSTEM_OCR_ROTATE.split(Config.LIST_SEPARATOR);

        for (String angle : angles) {
          // Rotate
          log.debug("Rotate image {} degrees", angle);
          double degree = Double.parseDouble(angle);
          ImageUtils.rotate(input, input, degree);
          text = doOcr(ocr, input);
          sb.append("\n-----------------------------\n");
          sb.append(text);
        }
      }

      return sb.toString();
    } else {
      log.warn("Undefined OCR application");
      throw new IOException("Undefined OCR application");
    }
  }

  /**
   * Performs OCR on image file
   */
  public String doOcr(File tmpFileIn) throws IOException {
    return doOcr(Config.SYSTEM_OCR, tmpFileIn);
  }

  /**
   * Performs OCR on image file
   */
  public String doOcr(String ocr, File tmpFileIn) throws IOException {
    BufferedReader stdout = null;
    FileInputStream fis = null;
    File tmpFileOut = null;
    String cmd = null;

    if (!ocr.isEmpty()) {
      try {
        // Create temp file
        tmpFileOut = File.createTempFile("okm", "");

        // Performs OCR
        HashMap<String, Object> hm = new HashMap<String, Object>();
        hm.put("fileIn", tmpFileIn.getPath());
        hm.put("fileOut", tmpFileOut.getPath());
        cmd = TemplateUtils.replace("SYSTEM_OCR", ocr, hm);
        ExecutionUtils.runCmd(cmd);

        // Read result
        fis = new FileInputStream(tmpFileOut.getPath() + ".txt");
        String text = IOUtils.toString(fis, "UTF-8");

        // Spellchecker
        if (Config.SYSTEM_OPENOFFICE_DICTIONARY.isEmpty()) {
          log.debug("TEXT: {}", text);
          return text;
        } else {
          text = DocumentUtils.spellChecker(text);
          log.debug("TEXT: {}", text);
          return text;
        }
      } catch (SecurityException e) {
        log.warn("Security exception executing command: " + cmd, e);
        throw new IOException(e.getMessage(), e);
      } catch (IOException e) {
        log.warn("IO exception executing command: " + cmd, e);
        throw new IOException(e.getMessage(), e);
      } catch (InterruptedException e) {
        log.warn("Interrupted exception executing command: " + cmd, e);
        throw new IOException(e.getMessage(), e);
      } catch (Exception e) {
        log.warn("Failed to extract OCR text", e);
        throw new IOException(e.getMessage(), e);
      } finally {
        IOUtils.closeQuietly(fis);
        IOUtils.closeQuietly(stdout);
        FileUtils.deleteQuietly(tmpFileOut);

        if (tmpFileOut != null) {
          FileUtils.deleteQuietly(new File(tmpFileOut.getPath() + ".txt"));
        }
      }
    } else {
      log.warn("Undefined OCR application");
      throw new IOException("Undefined OCR application");
    }
  }
}