PDF image extraction in Java

//---------------------------------------------------------------------------------------
// Copyright (c) 2001-2019 by PDFTron Systems Inc. All Rights Reserved.
// Consult legal.txt regarding legal and license information.
//---------------------------------------------------------------------------------------

package com.pdftron.android.pdfnetsdksamples.samples;

import com.pdftron.android.pdfnetsdksamples.OutputListener;
import com.pdftron.android.pdfnetsdksamples.PDFNetSample;
import com.pdftron.android.pdfnetsdksamples.R;
import com.pdftron.android.pdfnetsdksamples.util.Utils;
import com.pdftron.common.Matrix2D;
import com.pdftron.common.PDFNetException;
import com.pdftron.pdf.Element;
import com.pdftron.pdf.ElementReader;
import com.pdftron.pdf.Image;
import com.pdftron.pdf.PDFDoc;
import com.pdftron.pdf.PageIterator;
import com.pdftron.sdf.DictIterator;
import com.pdftron.sdf.Obj;
import com.pdftron.sdf.SDFDoc;

import java.util.ArrayList;

///-----------------------------------------------------------------------------------
/// This sample illustrates one approach to PDF image extraction
/// using PDFNet.
///
/// Note: Besides direct image export, you can also convert PDF images
/// to Java image, or extract uncompressed/compressed image data directly
/// using element.GetImageData() (e.g. as illustrated in ElementReaderAdv
/// sample project).
///-----------------------------------------------------------------------------------

public class ImageExtractTest extends PDFNetSample {

	private static OutputListener mOutputListener;

	private static ArrayList<String> mFileList = new ArrayList<>();

    public ImageExtractTest() {
        setTitle(R.string.sample_imageextract_title);
        setDescription(R.string.sample_imageextract_description);

        // The standard library does not support exporting to
        // PNG/TIFF formats, thus trying to export the PDF to
        // PNG or TIFF will fail. Please, comment out this call
        // if using the full library.
        // DisableRun();
    }

	@Override
	public void run(OutputListener outputListener) {
		super.run(outputListener);
		mOutputListener = outputListener;
		mFileList.clear();
		printHeader(outputListener);
        // Initialize PDFNet

        // Example 1:
        // Extract images by traversing the display list for
        // every page. With this approach it is possible to obtain
        // image positioning information and DPI.
        try (PDFDoc doc = new PDFDoc((Utils.getAssetTempFile(INPUT_PATH + "newsletter.pdf").getAbsolutePath()))) {
            doc.initSecurityHandler();
            ElementReader reader = new ElementReader();
            //  Read every page
            for (PageIterator itr = doc.getPageIterator(); itr.hasNext(); ) {
                reader.begin(itr.next());
                ImageExtract(reader);
                reader.end();
            }
            mOutputListener.println("Done.");
        } catch (Exception e) {
            mOutputListener.printError(e.getStackTrace());
        }

        mOutputListener.println("----------------------------------------------------------------");

        // Example 2:
        // Extract images by scanning the low-level document.
        try (PDFDoc doc = new PDFDoc((Utils.getAssetTempFile(INPUT_PATH + "newsletter.pdf").getAbsolutePath()))) {
            doc.initSecurityHandler();
            image_counter = 0;
            SDFDoc cos_doc = doc.getSDFDoc();
            long num_objs = cos_doc.xRefSize();
            for (int i = 1; i < num_objs; ++i) {
                Obj obj = cos_doc.getObj(i);
                if (obj != null && !obj.isFree() && obj.isStream()) {
                    // Process only images
                    DictIterator itr = obj.find("Type");
                    if (!itr.hasNext() || !itr.value().getName().equals("XObject"))
                        continue;

                    itr = obj.find("Subtype");
                    if (!itr.hasNext() || !itr.value().getName().equals("Image"))
                        continue;

                    Image image = new Image(obj);

                    mOutputListener.println("--> Image: " + (++image_counter));
                    mOutputListener.println("    Width: " + image.getImageWidth());
                    mOutputListener.println("    Height: " + image.getImageHeight());
                    mOutputListener.println("    BPC: " + image.getBitsPerComponent());

                    String fname = "image_extract2_" + image_counter;
                    String path = Utils.createExternalFile(fname, mFileList).getAbsolutePath();
                    image.export(path);

                    //String path= Utils.createExternalFile(fname + ".tif", mFileList).getAbsolutePath();
                    //image.exportAsTiff(path);

                    //String path = Utils.createExternalFile(fname + ".png", mFileList).getAbsolutePath();
                    //image.exportAsPng(path);
                }
            }
            
            mOutputListener.println("Done.");
        } catch (Exception e) {
            mOutputListener.printError(e.getStackTrace());
        }

		for (String file : mFileList) {
			addToFileList(file);
		}
		printFooter(outputListener);
	}

    // Relative paths to folders containing test files.

    static int image_counter = 0;

    static void ImageExtract(ElementReader reader) throws PDFNetException {
        Element element;
        while ((element = reader.next()) != null) {
            switch (element.getType()) {
                case Element.e_image:
                case Element.e_inline_image: {
                    mOutputListener.println("--> Image: " + (++image_counter));
                    mOutputListener.println("    Width: " + element.getImageWidth());
                    mOutputListener.println("    Height: " + element.getImageHeight());
                    mOutputListener.println("    BPC: " + element.getBitsPerComponent());

                    Matrix2D ctm = element.getCTM();
                    double x2 = 1, y2 = 1;
                    com.pdftron.pdf.Point p = ctm.multPoint(x2, y2);
                    mOutputListener.println(String.format("    Coords: x1=%.2f, y1=%.2f, x2=%.2f, y2=%.2f", ctm.getH(), ctm.getV(), p.x, p.y));

                    if (element.getType() == Element.e_image) {
                        Image image = new Image(element.getXObject());

                        String fname = "image_extract1_" + image_counter;

                        String path = Utils.createExternalFile(fname, mFileList).getAbsolutePath();
                        image.export(path);

                        //String path2 = Utils.createExternalFile(fname + ".tif", mFileList).getAbsolutePath();
                        //image.exportAsTiff(path2);

                        //String path3 = Utils.createExternalFile(fname + ".png", mFileList).getAbsolutePath();
                        //image.exportAsPng(path3);
                    }
                }
                break;
                case Element.e_form:        // Process form XObjects
                    reader.formBegin();
                    ImageExtract(reader);
                    reader.end();
                    break;
            }
        }
    }

}