PDFlib Cookbook

cookbook

text_output/invisible_text

Output invisible text on top of an image.

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/*
 * Invisible text:
 * Output invisible text on top of an image 
 *  
 * Place an image and create invisible text on top of it with the
 * "textrendering" parameter set to 3.  The most common scenario for this is
 * "scanned page with invisible OCR text" (which has been retrieved from the
 * scanned page in an earlier step with OCR).

 * Required software: PDFlib/PDFlib+PDI/PPS 9
 * Required data: image file
 */
package com.pdflib.cookbook.pdflib.text_output;

import com.pdflib.pdflib;
import com.pdflib.PDFlibException;

public class invisible_text {
    public static void main(String argv[]) {
        /* This is where the data files are. Adjust as necessary. */
        String searchpath = "../input";
        String outfile = "invisible_text.pdf";
        String title = "Invisible Text";

        pdflib p = null;

        String imagefile = "multi_page.tif";
        int font, image;
        int exitcode = 0;

        try {
            p = new pdflib();

            p.set_option("searchpath={" + searchpath + "}");

            /* This means we must check return values of load_font() etc. */
            p.set_option("errorpolicy=return");

            if (p.begin_document(outfile, "") == -1)
                throw new Exception("Error: " + p.get_errmsg());

            p.set_info("Creator", "PDFlib Cookbook");
            p.set_info("Title", title);

            font = p.load_font("Helvetica", "unicode", "");
            if (font == -1)
                throw new Exception("Error: " + p.get_errmsg());

            /* Load the image */
            image = p.load_image("auto", imagefile, "page=1");
            if (image == -1)
                throw new Exception("Error: " + p.get_errmsg());

            /* Start page */
            p.begin_page_ext(0, 0, "width=a4.width height=a4.height");

            /* Place the image */
            p.fit_image(image, 0, 0, "boxsize={595 842} fitmethod=meet");
            p.close_image(image);

            /* Save the current graphics state */
            p.save();

            /* Set the text rendering mode to "invisible text" */
            p.set_text_option("textrendering=3");

            /*
             * Output the text invisibly on top of the image with the rendering
             * mode set to "invisible text" above. (The text can be output on
             * top of the image or below the image.) The following text
             * resembles text retrieved from the scanned page via OCR.
             */
            p.setfont(font, 21);
            p.fit_textline("PDFlib GmbH M\u00fcnchen, Germany", 130, 750, "");
            p.fit_textline("www.pdflib.com", 215, 710, "");

            p.setfont(font, 28);
            p.fit_textline("Tutorial for", 120, 480, "");
            p.fit_textline("PDFlib, PDI, and PPS", 120, 445, "");

            p.setfont(font, 21);
            p.fit_textline("General Edition for", 195, 125, "");
            p.fit_textline("Cobol, C, C++, Java, Perl", 165, 95, "");
            p.fit_textline("PHP, Phyton, RPG, Ruby, and Tcl", 140, 70, "");

            /* Restore the current graphics state */
            p.restore();

            p.end_page_ext("");

            p.end_document("");
        }
        catch (PDFlibException e) {
            System.err.println("PDFlib exception occurred:");
            System.err.println("[" + e.get_errnum() + "] " + e.get_apiname()
                + ": " + e.get_errmsg());
            exitcode = 1;
        }
        catch (Exception e) {
            System.err.println(e);
            exitcode = 1;
        }
        finally {
            if (p != null) {
                p.delete();
            }
            System.exit(exitcode);
        }
    }
}