通过Java使用大图像压缩pdf
寻找一种将图像压缩为pdf格式并输出pdf进行存档的方法。我无法在创建图像之前对其进行压缩，因为这会影响打印质量。
每个pdf的大小约为8MB，其中大部分由2张图片组成。图片为png格式，并在生成过程中转换为pdf（使用了第三方生成器）
有没有一种方法可以在不使用第3方工具的情况下用Java压缩它们。我尝试使用pdfbox，itext和第3方exe（neevia），第3方工具是迄今为止唯一给我任何结果的工具（降低到大约一半MB），但我不想放弃对exe的控制。示例代码如下。
import java.io.BufferedReader;import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.Arrays;
import org.apache.pdfbox.exceptions.COSVisitorException;
import org.apache.pdfbox.pdmodel.PDDocument;
import org.apache.pdfbox.pdmodel.common.PDStream;
import com.itextpdf.text.DocumentException;
import com.itextpdf.text.pdf.PdfReader;
import com.itextpdf.text.pdf.PdfStamper;
import com.itextpdf.text.pdf.PdfWriter;
public class compressPDF {
public static void main (String[] args) throws IOException, DocumentException, COSVisitorException {
/*
* Using PDF Box
*/
PDDocument doc; // = new PDDocument();
doc = PDDocument.load("C:/_dev_env_/TEMP/compressPDF/TRPT_135002_1470_20131212_121423.PDF");
PDStream stream= new PDStream(doc);
stream.addCompression();
doc.save("C:/_dev_env_/TEMP/compressPDF/compressed_pdfBox.pdf");
doc.close();
/*
* Using itext
*/
PdfReader reader = new PdfReader("C:/_dev_env_/TEMP/compressPDF/TRPT_135002_1470_20131212_121423.PDF");
PdfStamper stamper = new PdfStamper(reader, new FileOutputStream("C:/_dev_env_/TEMP/compressPDF/compressed_Itext.pdf"), PdfWriter.VERSION_1_5);
stamper.setFullCompression();
stamper.getWriter().setCompressionLevel(50);
int total = reader.getNumberOfPages() + 1;
for (int i = 1; i < total; i++) {
reader.setPageContent(i, reader.getPageContent(i));
}
stamper.close();
reader.close();
/*
* Using 3rd party - Neevia
*/
try {
Process process = new ProcessBuilder("C:/Program Files (x86)/neeviaPDF.com/PDFcompress/cmdLine/CLcompr.exe","C:/_dev_env_/TEMP/compressPDF/TRPT_135002_1470_20131212_121423.PDF", "C:/_dev_env_/TEMP/compressPDF/compressed_Neevia.pdf").start();
InputStream is = process.getInputStream();
InputStreamReader isr = new InputStreamReader(is);
BufferedReader br = new BufferedReader(isr);
String line;
System.out.printf("Output of running %s is:", Arrays.toString(args));
while ((line = br.readLine()) != null) {
System.out.println(line);
}
} catch (Exception e) {
System.out.println(e);
} finally {
System.out.println("Created!!");
}
}
}
回答：
我使用下面的代码进行概念验证…起作用了：)感谢Bruno为我设定了正确的路径:)
package compressPDF;import java.awt.Graphics2D;
import java.awt.geom.AffineTransform;
import java.awt.image.BufferedImage;
import java.io.ByteArrayOutputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import javax.imageio.ImageIO;
import com.itextpdf.text.DocumentException;
import com.itextpdf.text.pdf.PRStream;
import com.itextpdf.text.pdf.PdfName;
import com.itextpdf.text.pdf.PdfNumber;
import com.itextpdf.text.pdf.PdfObject;
import com.itextpdf.text.pdf.PdfReader;
import com.itextpdf.text.pdf.PdfStamper;
import com.itextpdf.text.pdf.parser.PdfImageObject;
public class ResizeImage {
/** The resulting PDF file. */
//public static String RESULT = "results/part4/chapter16/resized_image.pdf";
/** The multiplication factor for the image. */
public static float FACTOR = 0.5f;
/**
* Manipulates a PDF file src with the file dest as result
* @param src the original PDF
* @param dest the resulting PDF
* @throws IOException
* @throws DocumentException
*/
public void manipulatePdf(String src, String dest) throws IOException, DocumentException {
PdfName key = new PdfName("ITXT_SpecialId");
PdfName value = new PdfName("123456789");
// Read the file
PdfReader reader = new PdfReader(src);
int n = reader.getXrefSize();
PdfObject object;
PRStream stream;
// Look for image and manipulate image stream
for (int i = 0; i < n; i++) {
object = reader.getPdfObject(i);
if (object == null || !object.isStream())
continue;
stream = (PRStream)object;
// if (value.equals(stream.get(key))) {
PdfObject pdfsubtype = stream.get(PdfName.SUBTYPE);
System.out.println(stream.type());
if (pdfsubtype != null && pdfsubtype.toString().equals(PdfName.IMAGE.toString())) {
PdfImageObject image = new PdfImageObject(stream);
BufferedImage bi = image.getBufferedImage();
if (bi == null) continue;
int width = (int)(bi.getWidth() * FACTOR);
int height = (int)(bi.getHeight() * FACTOR);
BufferedImage img = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
AffineTransform at = AffineTransform.getScaleInstance(FACTOR, FACTOR);
Graphics2D g = img.createGraphics();
g.drawRenderedImage(bi, at);
ByteArrayOutputStream imgBytes = new ByteArrayOutputStream();
ImageIO.write(img, "JPG", imgBytes);
stream.clear();
stream.setData(imgBytes.toByteArray(), false, PRStream.BEST_COMPRESSION);
stream.put(PdfName.TYPE, PdfName.XOBJECT);
stream.put(PdfName.SUBTYPE, PdfName.IMAGE);
stream.put(key, value);
stream.put(PdfName.FILTER, PdfName.DCTDECODE);
stream.put(PdfName.WIDTH, new PdfNumber(width));
stream.put(PdfName.HEIGHT, new PdfNumber(height));
stream.put(PdfName.BITSPERCOMPONENT, new PdfNumber(8));
stream.put(PdfName.COLORSPACE, PdfName.DEVICERGB);
}
}
// Save altered PDF
PdfStamper stamper = new PdfStamper(reader, new FileOutputStream(dest));
stamper.close();
reader.close();
}
/**
* Main method.
*
* @param args no arguments needed
* @throws DocumentException
* @throws IOException
*/
public static void main(String[] args) throws IOException, DocumentException {
//createPdf(RESULT);
new ResizeImage().manipulatePdf("C:/_dev_env_/TEMP/compressPDF/TRPT_135002_1470_20131212_121423.PDF", "C:/_dev_env_/TEMP/compressPDF/compressTest.pdf");
}
}
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