【JAVA】将PDF转化成图片

很多的开源库可以完成这个任务，但是效果都不理想，主要会产生以下问题：

1）分辨率很低，就是最后转化成的图片是缩略图，放大之后看不清楚；

2）不能支持中文，所有中文一律乱码；

3）图片各种混淆：大体是对的，但是个别元素出现混乱，尺寸位置不对等等；

上面说到的三种问题在各种类库中或多或少都存在。

A）实验下来效果最好的是QOPPA的开源库，在免费部分的测试情况下可以得到极为良好的效果。但是它最为不好的就是无条件加了水印，而且每行图片上面还加了网址，导致完全不可用了，而付费部分需要$400，实在买不起，所以虽然效果良好，但是还是不可行的。



B）再看ICEPDF这个开源库，这个库是最差的（也可能是我用的不好）



可以看到上面提到的问题1）和2）它全犯了！

C）再看PDFView这个开源库，转出效果如下：



怎么样，效果其实还可以的，对吧？但是问题是

1）分辨率低；2）背景么的了；

还有一个问题这张图片看不出来，我换一张：



插图无缘无故被放大了，遮住了文字，是问题3）。

D）再看JPEDAL开源库，这个库的普通转换效果如下：



这个不错吧，除了分辨率低，文字，背景全在，但是它也有上面的问题，插入的图片尺寸不对（这里就不展示了）

它最好的地方在于它还提供了高分辨率的转换，如下：



怎么样，够大够气派吧？超高分辨率，清晰的一米，剩下唯一的不好就是图片尺寸问题。

E）还有一个开源库叫PDFBox，还有PDFRender，这两个类库的问题都是分辨率不够高，PDFBox对中文的支持也存在很多问题，让人头疼。

我最后打算采用的方法就是D）的高分辨率转化方法。把测试代码展示如下：

1）转换类：

/**
* Example to convert PDF to highest possible quality images
* Also consider org.jpedal.examples.images.ConvertPagesToImages for faster if quality less important
*
* Useful blog article at http://www.jpedal.org/PDFblog/2009/07/pdf-to-image-quality/ *
* It can run from jar directly using the command
*
* java -cp libraries_needed org/jpedal/examples/images/ConvertPagesToHiResImages pdfFilepath inputValues
*
* where inputValues is 2 values
*
* First Parameter:  The full path including the name and extension of the target PDF file.
* Second Parameter:  The output image file type. Choices are tif, jpg and png.
*
* See also http://www.jpedal.org/javadoc/org/jpedal/constants/JPedalSettings.html for settings to customise
*/

/**
* ===========================================
* Java Pdf Extraction Decoding Access Library
* ===========================================
*
* Project Info:  http://www.jpedal.org * (C) Copyright 1997-2012, IDRsolutions and Contributors.
*
*   This file is part of JPedal
*
This source code is copyright IDRSolutions 2012

*
* ---------------
* ConvertPagesToHiResImages.java
* ---------------
*/

import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.util.*;

import javax.imageio.IIOImage;
import javax.imageio.ImageIO;
import javax.imageio.ImageTypeSpecifier;
import javax.imageio.metadata.IIOMetadata;
import javax.imageio.plugins.jpeg.JPEGImageWriteParam;
import javax.imageio.stream.ImageOutputStream;

import com.sun.imageio.plugins.jpeg.JPEGImageWriter;
import org.jpedal.PdfDecoder;
import org.jpedal.color.ColorSpaces;
import org.jpedal.exception.PdfException;
import org.jpedal.fonts.FontMappings;
import org.jpedal.objects.PdfPageData;
import org.jpedal.utils.LogWriter;
import org.jpedal.io.ColorSpaceConvertor;
import org.jpedal.io.JAIHelper;
import org.jpedal.constants.JPedalSettings;
import org.jpedal.constants.PageInfo;
import org.w3c.dom.Element;

public class ConvertPagesToHiResImages {

private static boolean debug = false;

/**correct separator for OS */
final static String separator = System.getProperty( "file.separator" );

//only used if between 0 and 1
private float JPEGcompression=-1f;

public ConvertPagesToHiResImages() {}

public static void main(String[] args) throws Exception {

/*
* Change these variables
*/
String fileType,pdfFile;

if(args!=null && args.length>1){

pdfFile = args[0];
fileType= args[1];

//open the file
if(pdfFile.toLowerCase().endsWith(".pdf") && (fileType.equals("jpg") || fileType.equals("jpeg") || fileType.equals("png") || fileType.equals("tiff") || fileType.equals("tif"))){
new ConvertPagesToHiResImages(fileType, pdfFile);
}else{ //open the directory

File testDir=new File(pdfFile);

if(testDir.isDirectory()){

/**
* get list of files and check directory
*/

String[] files = null;
File inputFiles;

/**make sure name ends with a deliminator for correct path later*/
if (!pdfFile.endsWith(separator))
pdfFile = pdfFile + separator;

try {
inputFiles = new File(pdfFile);

files = inputFiles.list();
} catch (Exception ee) {
LogWriter.writeLog("Exception trying to access file " + ee.getMessage());
}

/**now work through all pdf files*/
for (String file : files) {

if (file.toLowerCase().endsWith(".pdf"))
new ConvertPagesToHiResImages(fileType, pdfFile + file);
}
}else
System.out.println("The file to be processed has to be a pdf and the output filetype can only be jpg,png or tiff");
}
}else{
System.out.println("Not enough arguments passed in! Usage: \"C:\\examples\\1.pdf\" \"jpg\"");
}
}

/**
* main constructor to convert PDF to img
* @param fileType
* @param pdfFile
* @throws Exception
*/
public ConvertPagesToHiResImages(String fileType, String pdfFile) throws Exception {

long startTime=System.currentTimeMillis();

String outputPath = pdfFile.substring(0, pdfFile.toLowerCase().indexOf(".pdf")) + separator;
File outputPathFile = new File(outputPath);
if (!outputPathFile.exists() || !outputPathFile.isDirectory()) {
if (!outputPathFile.mkdirs()) {
if(debug)
System.err.println("Can't create directory " + outputPath);
}
}

//PdfDecoder object provides the conversion
final PdfDecoder decoder = new PdfDecoder(true);

//mappings for non-embedded fonts to use
//        FontMappings.setFontReplacements();

decoder.openPdfFile(pdfFile);

/**
* this process is very flaxible to we create a Map and pass in values to select what sort
* of results we want. There is a choice between methods used and image size. Larger images use more
* memory and are slower but look better
*/
Map mapValues = new HashMap();

/** USEFUL OPTIONS*/
//do not scale above this figure
mapValues.put(JPedalSettings.EXTRACT_AT_BEST_QUALITY_MAXSCALING, 2);

//alternatively secify a page size (aspect ratio preserved so will do best fit)
//set a page size (JPedal will put best fit to this)
mapValues.put(JPedalSettings.EXTRACT_AT_PAGE_SIZE, new String[]{"2000","1600"});

//which takes priority (default is false)
mapValues.put(JPedalSettings.PAGE_SIZE_OVERRIDES_IMAGE, Boolean.TRUE);

PdfDecoder.modifyJPedalParameters(mapValues);

if(debug)
System.out.println("pdf : " + pdfFile);

try{
/**
* allow output to multiple images with different values on each
*
* Note we REMOVE shapes as it is a new feature and we do not want to break existing functions
*/
String separation=System.getProperty("org.jpedal.separation");
if(separation!=null){

Object[] sepValues=new Object[]{7,"",Boolean.FALSE}; //default of normal
if(separation.equals("all")){
sepValues=new Object[]{PdfDecoder.RENDERIMAGES,"image_and_shapes",Boolean.FALSE,
PdfDecoder.RENDERIMAGES + PdfDecoder.REMOVE_RENDERSHAPES,"image_without_shapes",Boolean.FALSE,
PdfDecoder.RENDERTEXT,"text_and_shapes",Boolean.TRUE,
7,"all",Boolean.FALSE,
PdfDecoder.RENDERTEXT + PdfDecoder.REMOVE_RENDERSHAPES,"text_without_shapes",Boolean.TRUE
};
}

int sepCount =sepValues.length;
for(int seps=0;seps<sepCount;seps=seps+3){

decoder.setRenderMode((Integer) sepValues[seps]);
extractPageAsImage(fileType, outputPath, decoder,"_"+sepValues[seps+1], (Boolean) sepValues[seps + 2]); //boolean makes last transparent so we can see white text
}

}else //just get the page
extractPageAsImage(fileType, outputPath, decoder,"",false);

} finally {

decoder.closePdfFile();
}
System.out.println("time="+(System.currentTimeMillis()-startTime)/1000);

}

/**
* convenience method to get a page as a BufferedImage quickly
* - for bulk conversion, use the other methods
*/
public static BufferedImage getHiresPage(int pageNo, int scaling, String pdfFile){

BufferedImage imageToSave = null;

final PdfDecoder decoder = new PdfDecoder(true);

try{
//mappings for non-embedded fonts to use
//            FontMappings.setFontReplacements();

decoder.openPdfFile(pdfFile);

PdfPageData pageData = decoder.getPdfPageData();
int width=scaling*pageData.getCropBoxWidth(pageNo);
int height=scaling*pageData.getCropBoxHeight(pageNo);

Map mapValues = new HashMap();

/** USEFUL OPTIONS*/
//do not scale above this figure
mapValues.put(JPedalSettings.EXTRACT_AT_BEST_QUALITY_MAXSCALING, 2);

//alternatively secify a page size (aspect ratio preserved so will do best fit)
//set a page size (JPedal will put best fit to this)
mapValues.put(JPedalSettings.EXTRACT_AT_PAGE_SIZE, new String[]{String.valueOf(width),String.valueOf(height)});

//which takes priority (default is false)
mapValues.put(JPedalSettings.PAGE_SIZE_OVERRIDES_IMAGE, Boolean.TRUE);

PdfDecoder.modifyJPedalParameters(mapValues);

imageToSave = decoder.getPageAsHiRes(pageNo,null,false);

} catch (PdfException e) {
e.printStackTrace();
} finally {

decoder.closePdfFile();
}
return imageToSave;
}

/**
* actual conversion of a PDF page into an image
* @param fileType
* @param outputPath
* @param decoder
* @param prefix
* @param isTransparent
* @throws PdfException
* @throws IOException
*/
private void extractPageAsImage(String fileType, String outputPath, PdfDecoder decoder, String prefix, boolean isTransparent) throws PdfException, IOException {

//page range
int start=1, end=decoder.getPageCount();

//container if the user is creating a multi-image tiff
BufferedImage[] multiPages = new BufferedImage[1 + (end-start)];

/**
* set of JVM flags which allow user control on process
*/

//////////////////TIFF OPTIONS/////////////////////////////////////////

String multiPageFlag=System.getProperty("org.jpedal.multipage_tiff");
boolean isSingleOutputFile=multiPageFlag!=null && multiPageFlag.toLowerCase().equals("true");

String tiffFlag=System.getProperty("org.jpedal.compress_tiff");
boolean compressTiffs = tiffFlag!=null && tiffFlag.toLowerCase().equals("true");

//////////////////JPEG OPTIONS/////////////////////////////////////////

//allow user to specify value
String rawJPEGComp=System.getProperty("org.jpedal.compression_jpeg");
if(rawJPEGComp!=null){
try{
JPEGcompression=Float.parseFloat(rawJPEGComp);
}catch(Exception e){
e.printStackTrace();
}
if(JPEGcompression<0 || JPEGcompression>1)
throw new RuntimeException("Invalid value for JPEG compression - must be between 0 and 1");

}

String jpgFlag=System.getProperty("org.jpedal.jpeg_dpi");

///////////////////////////////////////////////////////////////////////

for (int pageNo = start; pageNo < end+1; pageNo++) {

if(debug)
System.out.println("page : " + pageNo);

/**
* example1 - ask JPedal to return from decoding if file takes too long (time is in millis)
* will reset after exit so call for each page
*/
//decoder.setPageDecodeStatus(DecodeStatus.Timeout,new Integer(20) );
/**
* example2 thread which will ask JPedal to time out and return from decoding
* will reset after exit so call for each page
*/
/**
Thread a=new Thread(){
public void run() {

while(true){
//simulate 2 second delay
try {
Thread.sleep(2000);
} catch (InterruptedException e) {
e.printStackTrace();  //To change body of catch statement use File | Settings | File Templates.
}

//tell JPedal to exit asap
decoder.setPageDecodeStatus(DecodeStatus.Timeout, Boolean.TRUE);

}
}
};

//simulate a second thread
a.start();

//see code after line decoder.getPageAsHiRes(pageNo); for tracking whether JPedal timed out and returned
/**/

/**
* If you are using decoder.getPageAsHiRes() after passing additional parameters into JPedal using the static method
* PdfDecoder.modifyJPedalParameters(), then getPageAsHiRes() wont necessarily be thread safe.  If you want to use
* getPageAsHiRes() and pass in additional parameters, in a thread safe mannor, please use the method
* getPageAsHiRes(int pageIndex, Map params) or getPageAsHiRes(int pageIndex, Map params, boolean isTransparent) and
* pass the additional parameters in directly to the getPageAsHiRes() method without calling PdfDecoder.modifyJPedalParameters()
* first.
*
* Please see org/jpedal/examples/images/ConvertPagesToImages.java.html for more details on how to use HiRes image conversion
*/
BufferedImage imageToSave = decoder.getPageAsHiRes(pageNo,null,isTransparent);

String imageFormat = System.getProperty("org.jpedal.imageType");
if(imageFormat!=null){
if(isNumber(imageFormat)){
int iFormat = Integer.parseInt(imageFormat);
if(iFormat>-1 && iFormat<14){
BufferedImage tempImage = new BufferedImage(imageToSave.getWidth(), imageToSave.getHeight(), iFormat);
Graphics2D g = tempImage.createGraphics();
g.drawImage(imageToSave, null, null);

imageToSave = tempImage;
}else{
System.err.println("Image Type is not valid. Value should be a digit between 0 - 13 based on the BufferedImage TYPE variables.");
}
}else{
System.err.println("Image Type provided is not an Integer. Value should be a digit between 0 - 13 based on the BufferedImage TYPE variables.");
}
}

//show status flag
/**
if(decoder.getPageDecodeStatus(DecodeStatus.Timeout))
System.out.println("Timeout on decoding");
else
System.out.println("Done");
/**/

decoder.flushObjectValues(true);

//System.out.println("w="+imageToSave.getWidth()+" h="+imageToSave.getHeight());
//image needs to be sRGB for JPEG
if(fileType.equals("jpg"))
imageToSave = ColorSpaceConvertor.convertToRGB(imageToSave);

String outputFileName;
if(isSingleOutputFile)
outputFileName = outputPath+ "allPages"+prefix+ '.' + fileType;
else{
/**
* create a name with zeros for if more than 9 pages appears in correct order
*/
String pageAsString=String.valueOf(pageNo);
String maxPageSize=String.valueOf(end);
int padding=maxPageSize.length()-pageAsString.length();
for(int ii=0;ii<padding;ii++)
pageAsString='0'+pageAsString;

outputFileName = outputPath + "page" + pageAsString +prefix + '.' + fileType;
}

//if just gray we can reduce memory usage by converting image to Grayscale

/**
* see what Colorspaces used and reduce image if appropriate
* (only does Gray at present)
*
* Can return null value if not sure
*/
Iterator colorspacesUsed=decoder.getPageInfo(PageInfo.COLORSPACES);

int nextID;
boolean isGrayOnly=colorspacesUsed!=null; //assume true and disprove

while(colorspacesUsed!=null && colorspacesUsed.hasNext()){
nextID= (Integer) (colorspacesUsed.next());

if(nextID!= ColorSpaces.DeviceGray && nextID!=ColorSpaces.CalGray)
isGrayOnly=false;
}

//draw onto GRAY image to reduce colour depth
//(converts ARGB to gray)
if(isGrayOnly){
BufferedImage image_to_save2=new BufferedImage(imageToSave.getWidth(),imageToSave.getHeight(), BufferedImage.TYPE_BYTE_GRAY);
image_to_save2.getGraphics().drawImage(imageToSave,0,0,null);
imageToSave = image_to_save2;
}

//put image in array if multi-images  (we save on last page in code below)
if(isSingleOutputFile)
multiPages[pageNo-start] = imageToSave;

//we save the image out here
if (imageToSave != null) {

/**BufferedImage does not support any dpi concept. A higher dpi can be created
* using JAI to convert to a higher dpi image*/

//shrink the page to 50% with graphics2D transformation
//- add your own parameters as needed
//you may want to replace null with a hints object if you
//want to fine tune quality.

/** example 1 biliniear scaling
AffineTransform scale = new AffineTransform();
scale.scale(.5, .5); //50% as a decimal
AffineTransformOp scalingOp =new AffineTransformOp(scale, null);
image_to_save =scalingOp.filter(image_to_save, null);

*/

if(JAIHelper.isJAIused())
JAIHelper.confirmJAIOnClasspath();

if(JAIHelper.isJAIused() && fileType.startsWith("tif")){

com.sun.media.jai.codec.TIFFEncodeParam params = new com.sun.media.jai.codec.TIFFEncodeParam();

if(compressTiffs)
params.setCompression(com.sun.media.jai.codec.TIFFEncodeParam.COMPRESSION_PACKBITS);

if(!isSingleOutputFile){
BufferedOutputStream os = new BufferedOutputStream(new FileOutputStream(outputFileName));

javax.media.jai.JAI.create("encode", imageToSave, os, "TIFF", params);
}else if(isSingleOutputFile && pageNo == end){
OutputStream out = new BufferedOutputStream(new FileOutputStream(outputFileName));
com.sun.media.jai.codec.ImageEncoder encoder = com.sun.media.jai.codec.ImageCodec.createImageEncoder("TIFF", out, params);
List vector = new ArrayList();
vector.addAll(Arrays.asList(multiPages).subList(1, multiPages.length));

params.setExtraImages(vector.iterator());

encoder.encode(multiPages[0]);
out.close();
}
}else if(isSingleOutputFile){
//non-JAI
} else if ((jpgFlag != null || rawJPEGComp!=null) && fileType.startsWith("jp") && JAIHelper.isJAIused()) {

saveAsJPEG(jpgFlag, imageToSave, JPEGcompression, new BufferedOutputStream(new FileOutputStream(outputFileName)));
} else {

BufferedOutputStream bos= new BufferedOutputStream(new FileOutputStream(new File(outputFileName)));
ImageIO.write(imageToSave, fileType, bos);
bos.flush();
bos.close();
}
//if you just want to save the image, use something like
//javax.imageio.ImageIO.write((java.awt.image.RenderedImage)image_to_save,"png",new java.io.FileOutputStream(output_dir + page + image_name+".png"));

}

imageToSave.flush();

if(debug){
System.out.println("Created : " + outputFileName);

}
}
}

/**test to see if string or number*/
private static boolean isNumber(String value) {

//assume true and see if proved wrong
boolean isNumber=true;

int charCount=value.length();
for(int i=0;i<charCount;i++){
char c=value.charAt(i);
if((c<'0')|(c>'9')){
isNumber=false;
i=charCount;
}
}

return isNumber;
}

private static void saveAsJPEG(String jpgFlag,BufferedImage image_to_save, float JPEGcompression, BufferedOutputStream fos) throws IOException {

//useful documentation at http://docs.oracle.com/javase/7/docs/api/javax/imageio/metadata/doc-files/jpeg_metadata.html //useful example program at http://johnbokma.com/java/obtaining-image-metadata.html to output JPEG data

//old jpeg class
//com.sun.image.codec.jpeg.JPEGImageEncoder jpegEncoder = com.sun.image.codec.jpeg.JPEGCodec.createJPEGEncoder(fos);
//com.sun.image.codec.jpeg.JPEGEncodeParam jpegEncodeParam = jpegEncoder.getDefaultJPEGEncodeParam(image_to_save);

// Image writer
JPEGImageWriter imageWriter = (JPEGImageWriter) ImageIO.getImageWritersBySuffix("jpeg").next();
ImageOutputStream ios = ImageIO.createImageOutputStream(fos);
imageWriter.setOutput(ios);

//and metadata
IIOMetadata imageMetaData = imageWriter.getDefaultImageMetadata(new ImageTypeSpecifier(image_to_save), null);

if (jpgFlag != null){

int dpi = 96;

try {
dpi = Integer.parseInt(jpgFlag);
} catch (Exception e) {
e.printStackTrace();
}

//old metadata
//jpegEncodeParam.setDensityUnit(com.sun.image.codec.jpeg.JPEGEncodeParam.DENSITY_UNIT_DOTS_INCH);
//jpegEncodeParam.setXDensity(dpi);
//jpegEncodeParam.setYDensity(dpi);

//new metadata
Element tree = (Element) imageMetaData.getAsTree("javax_imageio_jpeg_image_1.0");
Element jfif = (Element)tree.getElementsByTagName("app0JFIF").item(0);
jfif.setAttribute("Xdensity", Integer.toString(dpi));
jfif.setAttribute("Ydensity", Integer.toString(dpi));

}

if(JPEGcompression>=0 && JPEGcompression<=1f){

//old compression
//jpegEncodeParam.setQuality(JPEGcompression,false);

// new Compression
JPEGImageWriteParam jpegParams = (JPEGImageWriteParam) imageWriter.getDefaultWriteParam();
jpegParams.setCompressionMode(JPEGImageWriteParam.MODE_EXPLICIT);
jpegParams.setCompressionQuality(JPEGcompression);

}

//old write and clean
//jpegEncoder.encode(image_to_save, jpegEncodeParam);

//new Write and clean up
imageWriter.write(imageMetaData, new IIOImage(image_to_save, null, null), null);
ios.close();
imageWriter.dispose();

}
}

2）测试类：

public class Test {

/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
try {
ConvertPagesToHiResImages test =  new ConvertPagesToHiResImages("jpg", "/Users/mac/Desktop/pdftest/pdftest.pdf");
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}

}

其余的代码就不贴了，要用的话网上也有，读者自己搜一下，然后我遇到的最大的问题就是jar包的下载，各种难找。