如何提高PDF渲染器中图像的分辨率？
我想提高图像的分辨率。我使用了PDFRenderer-0.9.0
jar。它是从java.net 下载的，用于将PDF页面转换为图像。
我想将46_2.pdf
PDF文件转换为image。转换后的46_2.png图像尺寸较小612
x 792 [ width x height ]，
所以我想将图像尺寸增加到1200 x 1400 [ width x height]。
我以前尝试过 将PDF页面转换为PNG图像文件。有个问题only page is converted but text is
missing。因此，我尝试使用 库进行图像转换。
package com.pdfrenderer.examples;import java.awt.Graphics2D;
import java.awt.Image;
import java.awt.Rectangle;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.RandomAccessFile;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
import javax.imageio.ImageIO;
import com.sun.pdfview.PDFFile;
import com.sun.pdfview.PDFPage;
public class ConvertPdfPagesToImage {
public static void main(String[] args) {
try {
String sourceDir = "C:/PDFCopy/46_2.pdf";
String destinationDir = "C:/PDFCopy/";
File sourceFile = new File(sourceDir);
String fileName = sourceFile.getName().replace(".pdf", "");
if (sourceFile.exists()) {
RandomAccessFile raf = new RandomAccessFile(sourceFile, "r");
FileChannel channel = raf.getChannel();
ByteBuffer buf = channel.map(FileChannel.MapMode.READ_ONLY, 0, channel.size());
PDFFile pdf = new PDFFile(buf);
int pageNumber = 1;
for (int i = 0; i < pdf.getNumPages(); i++) {
PDFPage page = pdf.getPage(i);
// create the image
Rectangle rect = new Rectangle(0, 0, (int) page.getBBox().getWidth(), (int) page.getBBox().getHeight());
BufferedImage bufferedImage = new BufferedImage(rect.width, rect.height, BufferedImage.TYPE_INT_RGB);
// image width, // image height, // clip rect, // null for the ImageObserver, // fill background with white, // block until drawing is done
Image image = page.getImage(rect.width, rect.height, rect, null, true, true );
Graphics2D bufImageGraphics = bufferedImage.createGraphics();
bufImageGraphics.drawImage(image, 0, 0, null);
ImageIO.write(bufferedImage, "png", new File( destinationDir + fileName +"_"+ pageNumber +".png"));
pageNumber++;
}
} else {
System.err.println(sourceFile.getName() +" File not exists");
}
} catch (Exception e) {
e.printStackTrace();
}
}
}
回答：
pageNumber将从PDF文件46_2.pdf中选择的内容转换为具有所需尺寸的图像格式46_2.png。图像的分辨率随所需尺寸而增加。
如何将单个PDF页面转换为具有分辨率的png或jpeg图像格式。
package com.pdfrenderer.examples;import java.awt.Graphics2D;
import java.awt.Image;
import java.awt.Rectangle;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.RandomAccessFile;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
import javax.imageio.ImageIO;
import com.sun.pdfview.PDFFile;
import com.sun.pdfview.PDFPage;
public class PdfToImageWithDimensions {
public static void main(String[] args) {
try {
String sourceDir = "C:/PDFCopy/46_2.pdf";// PDF file must be placed in DataGet folder
String destinationDir = "C:/PDFCopy/Converted/";//Converted PDF page saved in this folder
File sourceFile = new File(sourceDir);
File destinationFile = new File(destinationDir);
String fileName = sourceFile.getName().replace(".pdf", "");
if (sourceFile.exists()) {
if (!destinationFile.exists()) {
destinationFile.mkdir();
System.out.println("Folder created in: "+ destinationFile.getCanonicalPath());
}
RandomAccessFile raf = new RandomAccessFile(sourceFile, "r");
FileChannel channel = raf.getChannel();
ByteBuffer buf = channel.map(FileChannel.MapMode.READ_ONLY, 0, channel.size());
PDFFile pdf = new PDFFile(buf);
int pageNumber = 1;// which PDF page to be convert
PDFPage page = pdf.getPage(pageNumber);
// image dimensions
int width = 1200;
int height = 1400;
// create the image
Rectangle rect = new Rectangle(0, 0, (int) page.getBBox().getWidth(), (int) page.getBBox().getHeight());
BufferedImage bufferedImage = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
// width & height, // clip rect, // null for the ImageObserver, // fill background with white, // block until drawing is done
Image image = page.getImage(width, height, rect, null, true, true );
Graphics2D bufImageGraphics = bufferedImage.createGraphics();
bufImageGraphics.drawImage(image, 0, 0, null);
File imageFile = new File( destinationDir + fileName +"_"+ pageNumber +".png" );// change file format here. Ex: .png, .jpg, .jpeg, .gif, .bmp
ImageIO.write(bufferedImage, "png", imageFile);
System.out.println(imageFile.getName() +" File created in: "+ destinationFile.getCanonicalPath());
} else {
System.err.println(sourceFile.getName() +" File not exists");
}
} catch (Exception e) {
e.printStackTrace();
}
}
}
转换后的文件保存在C:\PDFCopy\Converted文件夹中。下面是控制台输出。
46_2_1.png File created in: C:\PDFCopy\Converted感谢Jeff Friesen基于您的jRebel
示例，我在pdfrenderer中尝试过
如何在Java中使用PDF渲染器将所有PDF页面转换为png / jpeg / jpg / gif / bmp图像格式。待转换文件04-Request-
Headers.pdf
package com.pdfrenderer.examples;import java.awt.Graphics2D;
import java.awt.Image;
import java.awt.Rectangle;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.RandomAccessFile;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
import javax.imageio.ImageIO;
import com.sun.pdfview.PDFFile;
import com.sun.pdfview.PDFPage;
public class ConvertAllPDFPagesToImageWithDimenstions {
public static void main(String[] args) {
try {
String sourceDir = "C:/Documents/04-Request-Headers.pdf";// PDF file must be placed in DataGet folder
String destinationDir = "C:/Documents/Converted/";//Converted PDF page saved in this folder
File sourceFile = new File(sourceDir);
File destinationFile = new File(destinationDir);
String fileName = sourceFile.getName().replace(".pdf", "");
if (sourceFile.exists()) {
if (!destinationFile.exists()) {
destinationFile.mkdir();
System.out.println("Folder created in: "+ destinationFile.getCanonicalPath());
}
RandomAccessFile raf = new RandomAccessFile(sourceFile, "r");
FileChannel channel = raf.getChannel();
ByteBuffer buf = channel.map(FileChannel.MapMode.READ_ONLY, 0, channel.size());
PDFFile pdf = new PDFFile(buf);
System.out.println("Total Pages: "+ pdf.getNumPages());
int pageNumber = 1;
for (int i = 0; i < pdf.getNumPages(); i++) {
PDFPage page = pdf.getPage(i);
// image dimensions
int width = 1200;
int height = 1400;
// create the image
Rectangle rect = new Rectangle(0, 0, (int) page.getBBox().getWidth(), (int) page.getBBox().getHeight());
BufferedImage bufferedImage = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
// width & height, // clip rect, // null for the ImageObserver, // fill background with white, // block until drawing is done
Image image = page.getImage(width, height, rect, null, true, true );
Graphics2D bufImageGraphics = bufferedImage.createGraphics();
bufImageGraphics.drawImage(image, 0, 0, null);
File imageFile = new File( destinationDir + fileName +"_"+ pageNumber +".png" );// change file format here. Ex: .png, .jpg, .jpeg, .gif, .bmp
ImageIO.write(bufferedImage, "png", imageFile);
pageNumber++;
System.out.println(imageFile.getName() +" File created in Folder: "+ destinationFile.getCanonicalPath());
}
} else {
System.err.println(sourceFile.getName() +" File not exists");
}
} catch (Exception e) {
e.printStackTrace();
}
}
}
所有文件都保存在“ C:/Documents/Converted/文件夹”中。下面是控制台输出
Total Pages: 1304-Request-Headers_1.png File created in Folder: C:\Documents\Converted
04-Request-Headers_2.png File created in Folder: C:\Documents\Converted
04-Request-Headers_3.png File created in Folder: C:\Documents\Converted
04-Request-Headers_4.png File created in Folder: C:\Documents\Converted
04-Request-Headers_5.png File created in Folder: C:\Documents\Converted
04-Request-Headers_6.png File created in Folder: C:\Documents\Converted
04-Request-Headers_7.png File created in Folder: C:\Documents\Converted
04-Request-Headers_8.png File created in Folder: C:\Documents\Converted
04-Request-Headers_9.png File created in Folder: C:\Documents\Converted
04-Request-Headers_10.png File created in Folder: C:\Documents\Converted
04-Request-Headers_11.png File created in Folder: C:\Documents\Converted
04-Request-Headers_12.png File created in Folder: C:\Documents\Converted
04-Request-Headers_13.png File created in Folder: C:\Documents\Converted
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