尋找一種方法來壓縮PDF質量，并在JAVA中更改DPI。例如，我嘗試了PDFBox /itext庫，但仍然無法實現它。特別是如果當前的PDF DPI較高，我需要設置DPI（我需要降低掃描文檔的質量）請注意，我只看免費和開源庫。
2 回答
浮云間
TA貢獻1829條經驗 獲得超4個贊
最后，我找到了使用itextpdf庫的最佳解決方案。我們可以根據因子減少 DPI。
例如：因子 = 新數字像素/當前數字像素（系數 = 0.5f）
import java.awt.Graphics2D;
import java.awt.geom.AffineTransform;
import java.awt.image.BufferedImage;
import java.io.ByteArrayOutputStream;
import java.io.File;
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 ReduceSize {
public static final String SRC = "/Users/xxxx/Downloads/low/input.pdf";
public static final String DEST = "/Users/xxxx/Downloads/low/output.pdf";
public static final float FACTOR = 0.5f;
public static void main(String[] args) throws DocumentException, IOException {
File file = new File(DEST);
file.getParentFile().mkdirs();
new ReduceSize().manipulatePdf(SRC, DEST);
}
public void manipulatePdf(String src, String dest) throws DocumentException, IOException {
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 (!PdfName.IMAGE.equals(stream.getAsName(PdfName.SUBTYPE)))
continue;
if (!PdfName.DCTDECODE.equals(stream.getAsName(PdfName.FILTER)))
continue;
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);
if (width <= 0 || height <= 0)
continue;
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.NO_COMPRESSION);
stream.put(PdfName.TYPE, PdfName.XOBJECT);
stream.put(PdfName.SUBTYPE, PdfName.IMAGE);
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);
}
reader.removeUnusedObjects();
// Save altered PDF
PdfStamper stamper = new PdfStamper(reader, new FileOutputStream(dest));
stamper.setFullCompression();
stamper.close();
reader.close();
}
}
蝴蝶不菲
TA貢獻1810條經驗 獲得超4個贊
請嘗試完全壓縮
PdfReader reader = new PdfReader ( src) ;
PdfStamper stamper = new PdfStamper( reader, new FileOutputStream(dest) ,
Pdfwrlter. VERSION 1_5) ;
stamper.getWriter().setCompressionLeveI (9);
int total = reader . getNumberOfPages() + 1;
for (int i = 1; i < total; i++) {
reader . setpagecontent (i, reader . getpagecontent (i) ) ;
}
stamper. setFuIICompression() ;
stamper. close ( ) ;
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