Generate Thumbnail Images from PDF Documents

Aspose.PDF for Java Approach

Aspose.PDF for Java provides extensive support for dealing with PDF documents. It also supports the capability to convert the pages of PDF documents to a variety of image formats. The functionality described above can easily be achieved using Aspose.PDF for Java.

Aspose.PDF has distinct benefits:

• You don’t need to have Adobe Acrobat installed on your system to work with PDF files.
• Using Aspose.PDF for Java is simple and easy to understand as compared to Acrobat Automation.

If we need to convert PDF pages into JPEGs, the com.aspose.pdf.devices namespace provides a class named JpegDevice for rendering PDF pages into JPEG images. Please take a look over the following code snippet.

package com.aspose.pdf.examples;

import com.aspose.pdf.Document;
import com.aspose.pdf.devices.JpegDevice;
import com.aspose.pdf.devices.Resolution;

import java.io.FileOutputStream;
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.List;
import java.util.stream.Collectors;

public class ExampleGenerateThumbnails {
    private static String _dataDir = "/home/admin1/pdf-examples/Samples/";

    public static void GenerateThumbnails() throws IOException {
        // Retrieve names of all the PDF files in a particular directory
        List<String> fileEntries = null;
        try {
            fileEntries = Files.list(Paths.get(_dataDir)).filter(Files::isRegularFile)
                    .filter(path -> path.toString().endsWith(".pdf")).map(path -> path.toString())
                    .collect(Collectors.toList());

        } catch (IOException e) {
            // Error while reading the directory
        }

        // Iterate through all the files entries in array
        for (int counter = 0; counter < fileEntries.size(); counter++) {
            // Open document
            Document pdfDocument = new Document(fileEntries.get(counter));

            for (int pageCount = 1; pageCount <= 4; pageCount++) {
                FileOutputStream imageStream = new FileOutputStream(
                        _dataDir + "\\Thumbnails" + counter + "_" + pageCount + ".jpg");
                // Create Resolution object
                Resolution resolution = new Resolution(300);
                JpegDevice jpegDevice = new JpegDevice(45, 59, resolution, 100);
                // Convert a particular page and save the image to stream
                jpegDevice.process(pdfDocument.getPages().get_Item(pageCount), imageStream);
                // Close stream
                imageStream.close();
            }
        }

    }
}