http://pdfbox.Apache.org/ は、ページから画像を作成してから画像を拡大縮小できるため、探していることを実行できると思います。
サンプルコードから-
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.Apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.Apache.pdfbox;
import Java.awt.HeadlessException;
import Java.awt.Toolkit;
import Java.awt.image.BufferedImage;
import javax.imageio.ImageIO;
import Java.util.List;
import org.Apache.pdfbox.exceptions.InvalidPasswordException;
import org.Apache.pdfbox.pdmodel.PDDocument;
import org.Apache.pdfbox.pdmodel.PDPage;
import org.Apache.pdfbox.pdmodel.common.PDRectangle;
import org.Apache.pdfbox.util.PDFImageWriter;
/**
* Convert a PDF document to an image.
*
* @author <a href="[email protected]">Ben Litchfield</a>
* @version $Revision: 1.6 $
*/
public class PDFToImage
{
private static final String PASSWORD = "-password";
private static final String START_PAGE = "-startPage";
private static final String END_PAGE = "-endPage";
private static final String IMAGE_FORMAT = "-imageType";
private static final String OUTPUT_PREFIX = "-outputPrefix";
private static final String COLOR = "-color";
private static final String RESOLUTION = "-resolution";
private static final String CROPBOX = "-cropbox";
/**
* private constructor.
*/
private PDFToImage()
{
//static class
}
/**
* Infamous main method.
*
* @param args Command line arguments, should be one and a reference to a file.
*
* @throws Exception If there is an error parsing the document.
*/
public static void main( String[] args ) throws Exception
{
String password = "";
String pdfFile = null;
String outputPrefix = null;
String imageFormat = "jpg";
int startPage = 1;
int endPage = Integer.MAX_VALUE;
String color = "rgb";
int resolution;
float cropBoxLowerLeftX = 0;
float cropBoxLowerLeftY = 0;
float cropBoxUpperRightX = 0;
float cropBoxUpperRightY = 0;
try
{
resolution = Toolkit.getDefaultToolkit().getScreenResolution();
}
catch( HeadlessException e )
{
resolution = 96;
}
for( int i = 0; i < args.length; i++ )
{
if( args[i].equals( PASSWORD ) )
{
i++;
if( i >= args.length )
{
usage();
}
password = args[i];
}
else if( args[i].equals( START_PAGE ) )
{
i++;
if( i >= args.length )
{
usage();
}
startPage = Integer.parseInt( args[i] );
}
else if( args[i].equals( END_PAGE ) )
{
i++;
if( i >= args.length )
{
usage();
}
endPage = Integer.parseInt( args[i] );
}
else if( args[i].equals( IMAGE_FORMAT ) )
{
i++;
imageFormat = args[i];
}
else if( args[i].equals( OUTPUT_PREFIX ) )
{
i++;
outputPrefix = args[i];
}
else if( args[i].equals( COLOR ) )
{
i++;
color = args[i];
}
else if( args[i].equals( RESOLUTION ) )
{
i++;
resolution = Integer.parseInt(args[i]);
}
else if( args[i].equals( CROPBOX ) )
{
i++;
cropBoxLowerLeftX = Float.valueOf(args[i]).floatValue();
i++;
cropBoxLowerLeftY = Float.valueOf(args[i]).floatValue();
i++;
cropBoxUpperRightX = Float.valueOf(args[i]).floatValue();
i++;
cropBoxUpperRightY = Float.valueOf(args[i]).floatValue();
}
else
{
if( pdfFile == null )
{
pdfFile = args[i];
}
}
}
if( pdfFile == null )
{
usage();
}
else
{
if(outputPrefix == null)
{
outputPrefix = pdfFile.substring( 0, pdfFile.lastIndexOf( '.' ));
}
PDDocument document = null;
try
{
document = PDDocument.load( pdfFile );
//document.print();
if( document.isEncrypted() )
{
try
{
document.decrypt( password );
}
catch( InvalidPasswordException e )
{
if( args.length == 4 )//they supplied the wrong password
{
System.err.println( "Error: The supplied password is incorrect." );
System.exit( 2 );
}
else
{
//they didn't supply a password and the default of "" was wrong.
System.err.println( "Error: The document is encrypted." );
usage();
}
}
}
int imageType = 24;
if ("bilevel".equalsIgnoreCase(color))
{
imageType = BufferedImage.TYPE_BYTE_BINARY;
}
else if ("indexed".equalsIgnoreCase(color))
{
imageType = BufferedImage.TYPE_BYTE_INDEXED;
}
else if ("gray".equalsIgnoreCase(color))
{
imageType = BufferedImage.TYPE_BYTE_GRAY;
}
else if ("rgb".equalsIgnoreCase(color))
{
imageType = BufferedImage.TYPE_INT_RGB;
}
else if ("rgba".equalsIgnoreCase(color))
{
imageType = BufferedImage.TYPE_INT_ARGB;
}
else
{
System.err.println( "Error: the number of bits per pixel must be 1, 8 or 24." );
System.exit( 2 );
}
//si une cropBox a ete specifier, appeler la methode de modification de cropbox
//changeCropBoxes(PDDocument document,float a, float b, float c,float d)
if ( cropBoxLowerLeftX!=0 || cropBoxLowerLeftY!=0 || cropBoxUpperRightX!=0 || cropBoxUpperRightY!=0 )
{
changeCropBoxes(document,cropBoxLowerLeftX, cropBoxLowerLeftY, cropBoxUpperRightX, cropBoxUpperRightY);
}
//Make the call
PDFImageWriter imageWriter = new PDFImageWriter();
boolean success = imageWriter.writeImage(document, imageFormat, password,
startPage, endPage, outputPrefix, imageType, resolution);
if (!success)
{
System.err.println( "Error: no writer found for image format '"
+ imageFormat + "'" );
System.exit(1);
}
}
catch (Exception e)
{
System.err.println(e);
}
finally
{
if( document != null )
{
document.close();
}
}
}
}
/**
* This will print the usage requirements and exit.
*/
private static void usage()
{
System.err.println( "Usage: Java org.Apache.pdfbox.PDFToImage [OPTIONS] <PDF file>\n" +
" -password <password> Password to decrypt document\n" +
" -imageType <image type> (" + getImageFormats() + ")\n" +
" -outputPrefix <output prefix> Filename prefix for image files\n" +
" -startPage <number> The first page to start extraction(1 based)\n" +
" -endPage <number> The last page to extract(inclusive)\n" +
" -color <string> The color depth (valid: bilevel, indexed, gray, rgb, rgba)\n" +
" -resolution <number> The bitmap resolution in dpi\n" +
" -cropbox <number> <number> <number> <number> The page area to export\n" +
" <PDF file> The PDF document to use\n"
);
System.exit( 1 );
}
private static String getImageFormats()
{
StringBuffer retval = new StringBuffer();
String[] formats = ImageIO.getReaderFormatNames();
for( int i = 0; i < formats.length; i++ )
{
retval.append( formats[i] );
if( i + 1 < formats.length )
{
retval.append( "," );
}
}
return retval.toString();
}
private static void changeCropBoxes(PDDocument document,float a, float b, float c,float d)
{
List pages = document.getDocumentCatalog().getAllPages();
for( int i = 0; i < pages.size(); i++ )
{
System.out.println("resizing page");
PDPage page = (PDPage)pages.get( i );
PDRectangle rectangle = new PDRectangle();
rectangle.setLowerLeftX(a);
rectangle.setLowerLeftY(b);
rectangle.setUpperRightX(c);
rectangle.setUpperRightY(d);
page.setMediaBox(rectangle);
page.setCropBox(rectangle);
}
}
}
JPedalもご覧ください（詳細は http://www.jpedal.org/pdf_thumbnail.php ）
IcePdfは、PDFを読むために私が見た中で最高のものです（無料です）。 JPedalは素晴らしいですが、無料ではありません。
一般の人が送信できるPDFから画像を生成する場合は、（経験から）JVMをクラッシュさせるPDFを取得することを保証します。 （つまり、すべてのベクターグラフィックを含む多層PDFの場合）。 このpdf は、多くのライブラリをクラッシュさせる例です（ただし、Javascriptなどの面白いものがなくても完全に有効なPDF）です）。
多数のライブラリを使用しようとし、最終的にサムネイルの作成作業を画像操作用に高度に最適化されたCプログラムであるImageMagickに委任するという道をたどりました。