通过java压缩带有大图像的pdf

compress pdf with large images via java

提问by Daniel Mulcahy

Looking for a way to compress images in a pdf and to output a pdf for archiving. I cannot compress the images before creation as it would compromise the quality of the print.

寻找一种方法来压缩 pdf 中的图像并输出 pdf 以进行存档。我不能在创建之前压缩图像，因为它会影响打印质量。

The size of each pdf is around 8MB with the bulk of this being made up of 2 images. Images are in png format and are brought into pdf during generation(3rd party generator used)

每个 pdf 的大小约为 8MB，其中大部分由 2 张图像组成。图像为 png 格式，并在生成过程中转换为 pdf（使用第 3 方生成器）

Is there a way to compress these in java without using a 3rd party tool. I have tried with pdfbox, itext and a 3rd party exe(neevia), the 3rd party tool the only one that has given me any results so far(Down to around half a MB) but I do not want to relinquish control to an exe. Sample code is below.

有没有办法在不使用 3rd 方工具的情况下在 java 中压缩这些。我已经尝试过 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（低至大约半 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!!");
    }

}

}

采纳答案by Daniel Mulcahy

I used code below for a proof of concept... Works a treat :) Thanks to Bruno for setting me on the right path :)

我使用下面的代码来证明概念......很有用 :) 感谢布鲁诺让我走上正确的道路 :)

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");
}

}