TET Cookbook

cookbook

special/region_of_interest

Restrict text extraction to a particular "region of interest", i.e. some area on the page based on knowledge about the document layout.

Download Java Code  Show Output  Show Input (FontReporter.pdf) 

package com.pdflib.cookbook.tet.special;

import java.io.PrintStream;
import java.io.UnsupportedEncodingException;

import com.pdflib.TET;
import com.pdflib.TETException;

/**
 * Restrict text extraction to a particular "region of interest", i.e. some area
 * on the page based on knowledge about the document layout. This can easily be
 * implemented with the "includebox" and "excludebox" options of
 * open_page(). You can visualize page coordinates in Acrobat as follows:
 * - To display cursor coordinates in Acrobat DC use View, Show/Hide, Cursor
 *   Coordinates.
 * - The coordinates are displayed in the unit which is currently
 *   selected in Acrobat. To change the display units to points (as used in TET)
 *   in Acrobat DC proceed as follows: go to Edit, Preferences, Units &
 *   Guides, Units and select Points.
 *   
 *   Required software: TET 3
 * 
 */
class region_of_interest {
    /**
     * Global option list. The program expects the "resource" directory parallel to
     * the "java" directory.
     */
    private static final String GLOBAL_OPTLIST = "searchpath={../resource/cmap " + "../resource/glyphlist ../input}";

    /**
     * Document specific option list.
     */
    private static final String DOC_OPTLIST = "";

    /**
     * Page-specific option list. Here we define the region(s) of interest via an
     * "includebox" list of rectangles. In this case we define the includebox so the
     * footer line of the input document is not included.
     * <p>
     * As an alternative the footer line could be excluded with the "excludebox"
     * option. To try this with the input document, replace the "includebox" option
     * below with the following:
     * <p>
     * excludebox={{0 0 430 70}}
     */
    private static final String PAGE_OPTLIST = "granularity=page includebox={{30 70 430 670}}";

    /**
     * The encoding in which the output is sent to System.out. For running the
     * example in a Windows command window, you can set this for example to
     * "windows-1252" for getting Latin-1 output.
     */
    private static final String OUTPUT_ENCODING = System.getProperty("file.encoding");

    /**
     * For printing to System.out in the encoding specified via OUTPUT_ENCODING.
     */
    private static PrintStream out;

    /**
     * The name of the input file
     */
    private String filename;

    /**
     * Process a page from the input document.
     * 
     * @param tet    TET object
     * @param doc    TET document handle
     * @param pageno Page to process
     * 
     * @throws TETException An error occurred in the TET API
     */
    private static void process_page(TET tet, final int doc, int pageno) throws TETException {
        final int page = tet.open_page(doc, pageno, PAGE_OPTLIST);

        if (page == -1) {
            System.err.println("Error " + tet.get_errnum() + " in " + tet.get_apiname() + "(): " + tet.get_errmsg());
        } else {
            /* Retrieve all text fragments for the page */
            for (String text = tet.get_text(page); text != null; text = tet.get_text(page)) {
                out.println(text);
            }

            if (tet.get_errnum() != 0) {
                System.err
                        .println("Error " + tet.get_errnum() + " in " + tet.get_apiname() + "(): " + tet.get_errmsg());
            }

            tet.close_page(page);
        }
    }

    private void execute() {
        TET tet = null;
        int pageno = 0;

        try {
            tet = new TET();
            tet.set_option(GLOBAL_OPTLIST);

            final int doc = tet.open_document(filename, DOC_OPTLIST);
            if (doc == -1) {
                System.err
                        .println("Error " + tet.get_errnum() + " in " + tet.get_apiname() + "(): " + tet.get_errmsg());
                return;
            }

            /*
             * Loop over pages in the document
             */
            final int n_pages = (int) tet.pcos_get_number(doc, "length:pages");
            for (pageno = 1; pageno <= n_pages; ++pageno) {
                process_page(tet, doc, pageno);
            }

            tet.close_document(doc);
        } catch (TETException e) {
            if (pageno == 0) {
                System.err
                        .println("Error " + e.get_errnum() + " in " + e.get_apiname() + "(): " + e.get_errmsg() + "\n");
            } else {
                System.err.println("Error " + e.get_errnum() + " in " + e.get_apiname() + "() on page " + pageno + ": "
                        + e.get_errmsg() + "\n");
            }
            System.exit(1);
        } finally {
            tet.delete();
        }
    }

    /**
     * @param filename the name of the file for which the template will be generated
     */
    private region_of_interest(String filename) {
        this.filename = filename;
    }

    public static void main(String[] args) throws UnsupportedEncodingException {
        System.out.println("Using output encoding \"" + OUTPUT_ENCODING + "\"");
        out = new PrintStream(System.out, true, OUTPUT_ENCODING);

        if (args.length != 1) {
            out.println("usage: region_of_interest <infilename>");
            return;
        }

        region_of_interest t = new region_of_interest(args[0]);
        t.execute();
    }
}