Java tutorial
/* * Copyright 2016 King's College London, Richard Jackson <richgjackson@gmail.com>. * * 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. */ package uk.ac.kcl.tika.parsers; import org.apache.commons.io.IOUtils; import org.apache.commons.logging.LogFactory; import org.apache.tika.exception.TikaException; import org.apache.tika.io.TemporaryResources; import org.apache.tika.io.TikaInputStream; import org.apache.tika.metadata.Metadata; import org.apache.tika.mime.MediaType; import org.apache.tika.mime.MediaTypeRegistry; import org.apache.tika.parser.AbstractParser; import org.apache.tika.parser.CompositeParser; import org.apache.tika.parser.ParseContext; import org.apache.tika.parser.Parser; import org.apache.tika.parser.external.ExternalParser; import org.apache.tika.parser.image.ImageParser; import org.apache.tika.parser.image.TiffParser; import org.apache.tika.parser.jpeg.JpegParser; import org.apache.tika.parser.ocr.TesseractOCRConfig; import org.apache.tika.sax.XHTMLContentHandler; import org.xml.sax.ContentHandler; import org.xml.sax.SAXException; import javax.imageio.ImageIO; import java.awt.*; import java.awt.image.BufferedImage; import java.io.*; import java.util.*; import java.util.List; import java.util.concurrent.*; import static java.nio.charset.StandardCharsets.UTF_8; /** * TesseractOCRParser powered by tesseract-ocr engine. To enable this parser, * create a {@link TesseractOCRConfig} object and pass it through a * ParseContext. Tesseract-ocr must be installed and on system path or the path * to its root folder must be provided: * <p> * TesseractOCRConfig config = new TesseractOCRConfig();<br> * //Needed if tesseract is not on system path<br> * config.setTesseractPath(tesseractFolder);<br> * parseContext.set(TesseractOCRConfig.class, config);<br> * </p> * * */ public class TesseractOCRParser extends AbstractParser { private static final long serialVersionUID = -8167538283213097265L; private static final TesseractOCRConfig DEFAULT_CONFIG = new TesseractOCRConfig(); private static final Set<MediaType> SUPPORTED_TYPES = Collections.unmodifiableSet( new HashSet<MediaType>(Arrays.asList(new MediaType[] { MediaType.image("png"), MediaType.image("jpeg"), MediaType.image("tiff"), MediaType.image("x-ms-bmp"), MediaType.image("gif") }))); private static Map<String, Boolean> TESSERACT_PRESENT = new HashMap<String, Boolean>(); @Override public Set<MediaType> getSupportedTypes(ParseContext context) { // If Tesseract is installed, offer our supported image types TesseractOCRConfig config = context.get(TesseractOCRConfig.class, DEFAULT_CONFIG); if (hasTesseract(config)) return SUPPORTED_TYPES; // Otherwise don't advertise anything, so the other image parsers // can be selected instead return Collections.emptySet(); } private void setEnv(TesseractOCRConfig config, ProcessBuilder pb) { String tessdataPrefix = "TESSDATA_PREFIX"; Map<String, String> env = pb.environment(); if (!config.getTessdataPath().isEmpty()) { env.put(tessdataPrefix, config.getTessdataPath()); } else if (!config.getTesseractPath().isEmpty()) { env.put(tessdataPrefix, config.getTesseractPath()); } } private boolean hasTesseract(TesseractOCRConfig config) { // Fetch where the config says to find Tesseract String tesseract = config.getTesseractPath() + getTesseractProg(); // Have we already checked for a copy of Tesseract there? if (TESSERACT_PRESENT.containsKey(tesseract)) { return TESSERACT_PRESENT.get(tesseract); } // Try running Tesseract from there, and see if it exists + works String[] checkCmd = { tesseract }; boolean hasTesseract = ExternalParser.check(checkCmd); TESSERACT_PRESENT.put(tesseract, hasTesseract); return hasTesseract; } public void parse(Image image, ContentHandler handler, Metadata metadata, ParseContext context) throws IOException, SAXException, TikaException { TemporaryResources tmp = new TemporaryResources(); FileOutputStream fos = null; TikaInputStream tis = null; try { int w = image.getWidth(null); int h = image.getHeight(null); BufferedImage bImage = new BufferedImage(w, h, BufferedImage.TYPE_INT_RGB); File file = tmp.createTemporaryFile(); fos = new FileOutputStream(file); ImageIO.write(bImage, "png", fos); tis = TikaInputStream.get(file); parse(tis, handler, metadata, context); } finally { tmp.dispose(); if (tis != null) tis.close(); if (fos != null) fos.close(); } } @Override public void parse(InputStream stream, ContentHandler handler, Metadata metadata, ParseContext context) throws IOException, SAXException, TikaException { TesseractOCRConfig config = context.get(TesseractOCRConfig.class, DEFAULT_CONFIG); // If Tesseract is not on the path with the current config, do not try to run OCR // getSupportedTypes shouldn't have listed us as handling it, so this should only // occur if someone directly calls this parser, not via DefaultParser or similar if (!hasTesseract(config)) return; XHTMLContentHandler xhtml = new XHTMLContentHandler(handler, metadata); TemporaryResources tmp = new TemporaryResources(); File output = null; try { TikaInputStream tikaStream = TikaInputStream.get(stream, tmp); File input = tikaStream.getFile(); long size = tikaStream.getLength(); if (size >= config.getMinFileSizeToOcr() && size <= config.getMaxFileSizeToOcr()) { output = tmp.createTemporaryFile(); doOCR(input, output, config); // Tesseract appends .txt to output file name output = new File(output.getAbsolutePath() + ".txt"); if (output.exists()) extractOutput(new FileInputStream(output), xhtml); } // Temporary workaround for TIKA-1445 - until we can specify // composite parsers with strategies (eg Composite, Try In Turn), // always send the image onwards to the regular parser to have // the metadata for them extracted as well _TMP_IMAGE_METADATA_PARSER.parse(tikaStream, handler, metadata, context); } finally { tmp.dispose(); if (output != null) { output.delete(); } } } // TIKA-1445 workaround parser private static Parser _TMP_IMAGE_METADATA_PARSER = new CompositeImageParser(); private static class CompositeImageParser extends CompositeParser { private static final long serialVersionUID = -2398203346206381382L; private static List<Parser> imageParsers = Arrays .asList(new Parser[] { new ImageParser(), new JpegParser(), new TiffParser() }); CompositeImageParser() { super(new MediaTypeRegistry(), imageParsers); } } /** * Run external tesseract-ocr process. * * @param input * File to be ocred * @param output * File to collect ocr result * @param config * Configuration of tesseract-ocr engine * @throws TikaException * if the extraction timed out * @throws IOException * if an input error occurred */ private void doOCR(File input, File output, TesseractOCRConfig config) throws IOException, TikaException { String[] cmd = { config.getTesseractPath() + getTesseractProg(), input.getPath(), output.getPath(), "-l", config.getLanguage(), "-psm", config.getPageSegMode() }; ProcessBuilder pb = new ProcessBuilder(cmd); setEnv(config, pb); final Process process = pb.start(); process.getOutputStream().close(); InputStream out = process.getInputStream(); InputStream err = process.getErrorStream(); logStream("OCR MSG", out, input); logStream("OCR ERROR", err, input); FutureTask<Integer> waitTask = new FutureTask<Integer>(new Callable<Integer>() { public Integer call() throws Exception { return process.waitFor(); } }); Thread waitThread = new Thread(waitTask); waitThread.start(); try { waitTask.get(config.getTimeout(), TimeUnit.SECONDS); } catch (InterruptedException e) { waitThread.interrupt(); process.destroy(); Thread.currentThread().interrupt(); throw new TikaException("TesseractOCRParser interrupted", e); } catch (ExecutionException e) { // should not be thrown } catch (TimeoutException e) { waitThread.interrupt(); process.destroy(); throw new TikaException("TesseractOCRParser timeout", e); } } /** * Reads the contents of the given stream and write it to the given XHTML * content handler. The stream is closed once fully processed. * * @param stream * Stream where is the result of ocr * @param xhtml * XHTML content handler * @throws SAXException * if the XHTML SAX events could not be handled * @throws IOException * if an input error occurred */ private void extractOutput(InputStream stream, XHTMLContentHandler xhtml) throws SAXException, IOException { xhtml.startDocument(); xhtml.startElement("div"); try (Reader reader = new InputStreamReader(stream, UTF_8)) { char[] buffer = new char[1024]; for (int n = reader.read(buffer); n != -1; n = reader.read(buffer)) { if (n > 0) xhtml.characters(buffer, 0, n); } } xhtml.endElement("div"); xhtml.endDocument(); } /** * Starts a thread that reads the contents of the standard output or error * stream of the given process to not block the process. The stream is closed * once fully processed. */ private void logStream(final String logType, final InputStream stream, final File file) { new Thread() { public void run() { Reader reader = new InputStreamReader(stream, UTF_8); StringBuilder out = new StringBuilder(); char[] buffer = new char[1024]; try { for (int n = reader.read(buffer); n != -1; n = reader.read(buffer)) out.append(buffer, 0, n); } catch (IOException e) { } finally { IOUtils.closeQuietly(stream); } String msg = out.toString(); LogFactory.getLog(TesseractOCRParser.class).debug(msg); } }.start(); } static String getTesseractProg() { return System.getProperty("os.name").startsWith("Windows") ? "tesseract.exe" : "tesseract"; } }