PDFlib

determine_image_resolution

For each image, fetch the width and height in pixels from images [] and the width and height in point from the TET_image_info structure. Determine the image resolution in dpi. As the meaning of the dpi information changes if the image is rotated or skewed, a warning is printed in these cases.

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package com.pdflib.cookbook.tet.image;


import java.io.PrintStream;

import java.io.UnsupportedEncodingException;

import java.text.NumberFormat;


import com.pdflib.TET;

import com.pdflib.TETException;


/**

 * For each image, fetch the width and height in pixels from images[] and the

 * width and height in point from the TET_image_info structure. Determine the

 * image resolution in dpi. As the meaning of the dpi information changes

 * if the image is rotated or skewed, a warning is printed in these cases.

 * <p>

 * Required software: TET 3

 * <p>

 * Required data: PDF document

 *

 * @version $Id: determine_image_resolution.java,v 1.4 2014/05/26 13:02:11 rjs Exp $

 */

public class determine_image_resolution

{

    /**

     * Global option list

     */

    static final String GLOBAL_OPTLIST = "searchpath={../resource/cmap "

        + "../resource/glyphlist ../input}";

   

    /**

     * Document-specific option list

     */

    static final String DOC_OPTLIST = "";

   

    /**

     * Page-specific option list

     */

    static final String PAGE_OPTLIST = "granularity=page";

   

    /**

     * Basic image extract options (more below)

     */

    static final String BASE_IMAGE_OPTLIST = "compression=auto format=auto";


    /**

     * 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;

   

    public static void main(String argv[]) throws UnsupportedEncodingException {

        System.out.println("Using output encoding \"" + OUTPUT_ENCODING + "\"");

        out = new PrintStream(System.out, true, OUTPUT_ENCODING);


        TET tet = null;


        try {

            if (argv.length != 1) {

                throw new Exception(

                        "usage: determine_image_resolution <filename>");

            }


            NumberFormat dpiFormat = NumberFormat.getInstance();

            dpiFormat.setMinimumFractionDigits(0);

            dpiFormat.setMaximumFractionDigits(2);


            tet = new TET();


            tet.set_option(GLOBAL_OPTLIST);


            int doc = tet.open_document(argv[0], DOC_OPTLIST);

            if (doc == -1) {

                throw new Exception("Error " + tet.get_errnum() + "in "

                        + tet.get_apiname() + "(): " + tet.get_errmsg());

            }


            /* get number of pages in the document */

            int n_pages = (int) tet.pcos_get_number(doc, "length:pages");


            /* loop over pages */

            for (int pageno = 1; pageno <= n_pages; ++pageno) {

                int page = tet.open_page(doc, pageno, PAGE_OPTLIST);


                if (page < 0) {

                    print_tet_error(tet, pageno);

                    continue; /* try next page */

                }


                /* Retrieve all images on the page */

                int imageno = 0;

                while (tet.get_image_info(page) == 1) {

                    /*

                     * Calculate the DPI values for x and y direction, and

                     * warn if the image is rotated or skewed.

                     */

                    String imagePath = "images[" + tet.imageid + "]";

                    int width = (int) tet.pcos_get_number(doc,

                                            imagePath + "/Width");

                    int height = (int) tet.pcos_get_number(doc,

                            imagePath + "/Height");

                   

                    double xDpi = 72 * width / tet.width;

                    double yDpi = 72 * height / tet.height;

                   

                    out.println("Page " + pageno + " image " + imageno + ": "

                            + "resolution (DPI): x="

                            + dpiFormat.format(xDpi) + " y="

                            + dpiFormat.format(yDpi));


                    if (tet.alpha != 0 || tet.beta != 0) {

                        out.println(

                            "  Warning: image is rotated and/or skewed (alpha="

                                + tet.alpha + ", beta=" + tet.beta + "), "

                                + "DPI value may be meaningless");

                    }


                    imageno++;

                }


                if (tet.get_errnum() != 0) {

                    print_tet_error(tet, pageno);

                }


                tet.close_page(page);

            }


            tet.close_document(doc);

        }

        catch (TETException e) {

            System.err.println("TET exception occurred in extractor sample:");

            System.err.println("[" + e.get_errnum() + "] " + e.get_apiname()

                    + ": " + e.get_errmsg());

            System.exit(1);

        }

        catch (Exception e) {

            System.err.println(e.getMessage());

            System.exit(1);

        }

        finally {

            if (tet != null) {

                tet.delete();

            }

        }

    }


    /**

     * Report a TET error.

     *

     * @param tet

     *            The TET object

     * @param pageno

     *            The page number on which the error occurred

     */

    private static void print_tet_error(TET tet, int pageno) {

        System.err.println("Error " + tet.get_errnum() + " in  "

                + tet.get_apiname() + "() on page " + pageno + ": "

                + tet.get_errmsg());

    }

}