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# Tess4J ## Description: A Java JNA wrapper for Tesseract OCR API. Tess4J is released and distributed under the Apache License, v2.0. ## Features: The library provides optical character recognition (OCR) support for: TIFF, JPEG, GIF, PNG, and BMP image formats Multi-page TIFF images PDF document format
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/**
 * Copyright @ 2009 Quan Nguyen
 *
 * 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 net.sourceforge.tess4j.util;

import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FilenameFilter;
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Comparator;
import java.util.List;

import org.ghost4j.Ghostscript;
import org.ghost4j.GhostscriptException;
import org.slf4j.LoggerFactory;

/**
 * PDF utilities based on Ghostscript.
 */
public class PdfGsUtilities {

    public static final String GS_INSTALL = "\nPlease download, install GPL Ghostscript from http://www.ghostscript.com\nand/or set the appropriate path variable.";

    private static final org.slf4j.Logger logger = LoggerFactory.getLogger(new LoggHelper().toString());

    /**
     * Converts PDF to TIFF format.
     *
     * @param inputPdfFile input file
     * @return a multi-page TIFF image
     * @throws IOException
     */
    public static File convertPdf2Tiff(File inputPdfFile) throws IOException {
        File[] pngFiles = null;

        try {
            pngFiles = convertPdf2Png(inputPdfFile);
            File tiffFile = File.createTempFile("multipage", ".tif");

            // put PNG images into a single multi-page TIFF image for return
            ImageIOHelper.mergeTiff(pngFiles, tiffFile);
            return tiffFile;
        } finally {
            if (pngFiles != null && pngFiles.length > 0) {
                // get the working directory of the PNG files
                File pngDirectory = new File(pngFiles[0].getParent());
                // delete temporary PNG images
                for (File tempFile : pngFiles) {
                    tempFile.delete();
                }

                pngDirectory.delete();
            }
        }
    }

    /**
     * Converts PDF to PNG format.
     *
     * @param inputPdfFile input file
     * @return an array of PNG images
     * @throws java.io.IOException
     */
    public synchronized static File[] convertPdf2Png(File inputPdfFile) throws IOException {
        Path path = Files.createTempDirectory("tessimages");
        File imageDir = path.toFile();

        //get Ghostscript instance
        Ghostscript gs = Ghostscript.getInstance();

        //prepare Ghostscript interpreter parameters
        //refer to Ghostscript documentation for parameter usage
        List gsArgs = new ArrayList();
        gsArgs.add("-gs");
        gsArgs.add("-dNOPAUSE");
        gsArgs.add("-dQUIET");
        gsArgs.add("-dBATCH");
        gsArgs.add("-dSAFER");
        gsArgs.add("-sDEVICE=pnggray");
        gsArgs.add("-r300");
        gsArgs.add("-dGraphicsAlphaBits=4");
        gsArgs.add("-dTextAlphaBits=4");
        gsArgs.add("-sOutputFile=" + imageDir.getPath() + "/workingimage%04d.png");
        gsArgs.add(inputPdfFile.getPath());

        //execute and exit interpreter
        try {
            synchronized (gs) {
                gs.initialize(gsArgs.toArray(new String[0]));
                gs.exit();
            }
        } catch (UnsatisfiedLinkError e) {
            logger.error(e.getMessage());
            throw new RuntimeException(getMessage(e.getMessage()));
        } catch (NoClassDefFoundError e) {
            logger.error(e.getMessage());
            throw new RuntimeException(getMessage(e.getMessage()));
        } catch (GhostscriptException e) {
            logger.error(e.getMessage());
            throw new RuntimeException(e.getMessage());
        } finally {
            if (imageDir.list().length == 0) {
                imageDir.delete();
            }

            //delete interpreter instance (safer)
            try {
                Ghostscript.deleteInstance();
            } catch (GhostscriptException e) {
                //nothing
            }
        }

        // find working files
        File[] workingFiles = imageDir.listFiles(new FilenameFilter() {

            @Override
            public boolean accept(File dir, String name) {
                return name.toLowerCase().matches("workingimage\\d{4}\\.png$");
            }
        });

        Arrays.sort(workingFiles, new Comparator() {
            @Override
            public int compare(File f1, File f2) {
                return f1.getName().compareTo(f2.getName());
            }
        });

        return workingFiles;
    }

    /**
     * Splits PDF.
     *
     * @param inputPdfFile input file
     * @param outputPdfFile output file
     * @param firstPage begin page
     * @param lastPage end page
     */
    public static void splitPdf(File inputPdfFile, File outputPdfFile, int firstPage, int lastPage) {
        //get Ghostscript instance
        Ghostscript gs = Ghostscript.getInstance();

        //prepare Ghostscript interpreter parameters
        //refer to Ghostscript documentation for parameter usage
        //gs -sDEVICE=pdfwrite -dNOPAUSE -dQUIET -dBATCH -dFirstPage=m -dLastPage=n -sOutputFile=out.pdf in.pdf
        List gsArgs = new ArrayList();
        gsArgs.add("-gs");
        gsArgs.add("-dNOPAUSE");
        gsArgs.add("-dQUIET");
        gsArgs.add("-dBATCH");
        gsArgs.add("-sDEVICE=pdfwrite");
        if (firstPage > 0) {
            gsArgs.add("-dFirstPage=" + firstPage);
        }
        if (lastPage > 0) {
            gsArgs.add("-dLastPage=" + lastPage);
        }
        gsArgs.add("-sOutputFile=" + outputPdfFile.getPath());
        gsArgs.add(inputPdfFile.getPath());

        //execute and exit interpreter
        try {
            synchronized (gs) {
                gs.initialize(gsArgs.toArray(new String[0]));
                gs.exit();
            }
        } catch (UnsatisfiedLinkError e) {
            logger.error(e.getMessage());
            throw new RuntimeException(getMessage(e.getMessage()));
        } catch (NoClassDefFoundError e) {
            logger.error(e.getMessage());
            throw new RuntimeException(getMessage(e.getMessage()));
        } catch (GhostscriptException e) {
            logger.error(e.getMessage());
            throw new RuntimeException(e.getMessage());
        } finally {
            //delete interpreter instance (safer)
            try {
                Ghostscript.deleteInstance();
            } catch (GhostscriptException e) {
                //nothing
            }
        }
    }

    /**
     * Gets PDF Page Count.
     *
     * @param inputPdfFile input file
     * @return number of pages
     */
    public static int getPdfPageCount(File inputPdfFile) {
        String inputFile = inputPdfFile.getPath().replace('\\', '/');
        //get Ghostscript instance
        Ghostscript gs = Ghostscript.getInstance();

        //prepare Ghostscript interpreter parameters
        //refer to Ghostscript documentation for parameter usage
        //gs -q -dNODISPLAY -c "(input.pdf) (r) file runpdfbegin pdfpagecount = quit"
        List gsArgs = new ArrayList();
        gsArgs.add("-gs");
        gsArgs.add("-dNOPAUSE");
        gsArgs.add("-dQUIET");
        gsArgs.add("-dNODISPLAY");
        gsArgs.add("-dBATCH");
        gsArgs.add("--permit-file-read=" + inputFile);
        gsArgs.add("-c");
        String cValue = String.format("(%s) (r) file runpdfbegin pdfpagecount = quit", inputFile);
        gsArgs.add(cValue);

        int pageCount = 0;
        ByteArrayOutputStream os;

        //execute and exit interpreter
        try {
            synchronized (gs) {
                //output
                os = new ByteArrayOutputStream();
                gs.setStdOut(os);
                gs.initialize(gsArgs.toArray(new String[0]));
                pageCount = Integer.parseInt(os.toString().trim());
                os.close();
            }
        } catch (UnsatisfiedLinkError e) {
            logger.error(e.getMessage());
            throw new RuntimeException(getMessage(e.getMessage()));
        } catch (NoClassDefFoundError e) {
            logger.error(e.getMessage());
            throw new RuntimeException(getMessage(e.getMessage()));
        } catch (GhostscriptException e) {
            logger.error(e.getMessage());
            throw new RuntimeException(e.getMessage());
        } catch (Exception e) {
            logger.error(e.getMessage());
        } finally {
            //delete interpreter instance (safer)
            try {
                Ghostscript.deleteInstance();
            } catch (GhostscriptException e) {
                //nothing
            }
        }

        return pageCount;
    }

    /**
     * Merges PDF files.
     *
     * @param inputPdfFiles array of input files
     * @param outputPdfFile output file
     */
    public static void mergePdf(File[] inputPdfFiles, File outputPdfFile) {
        //get Ghostscript instance
        Ghostscript gs = Ghostscript.getInstance();

        //prepare Ghostscript interpreter parameters
        //refer to Ghostscript documentation for parameter usage
        //gs -sDEVICE=pdfwrite -dNOPAUSE -dQUIET -dBATCH -sOutputFile=out.pdf in1.pdf in2.pdf in3.pdf
        List gsArgs = new ArrayList();
        gsArgs.add("-gs");
        gsArgs.add("-dNOPAUSE");
        gsArgs.add("-dQUIET");
        gsArgs.add("-dBATCH");
        gsArgs.add("-sDEVICE=pdfwrite");
        gsArgs.add("-sOutputFile=" + outputPdfFile.getPath());

        for (File inputPdfFile : inputPdfFiles) {
            gsArgs.add(inputPdfFile.getPath());
        }

        //execute and exit interpreter
        try {
            synchronized (gs) {
                gs.initialize(gsArgs.toArray(new String[0]));
                gs.exit();
            }
        } catch (UnsatisfiedLinkError e) {
            logger.error(e.getMessage());
            throw new RuntimeException(getMessage(e.getMessage()));
        } catch (NoClassDefFoundError e) {
            logger.error(e.getMessage());
            throw new RuntimeException(getMessage(e.getMessage()));
        } catch (GhostscriptException e) {
            logger.error(e.getMessage());
            throw new RuntimeException(e.getMessage());
        } finally {
            //delete interpreter instance (safer)
            try {
                Ghostscript.deleteInstance();
            } catch (GhostscriptException e) {
                //nothing
            }
        }
    }

    static String getMessage(String message) {
        if (message.contains("library 'gs") || message.contains("ghost4j")) {
            return message + GS_INSTALL;
        }
        return message;
    }
}