Java 如何提高PDF渲染器中图像的分辨率？
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/21064270/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
How to increase the resolution of image in PDF renderer?
提问by UdayKiran Pulipati
I want to increase the resolution of a image. I used PDFRenderer-0.9.0jar . It is downloaded from java.net for converting PDF pages to images.
我想提高图像的分辨率。我使用了PDFRenderer-0.9.0jar 。它是从java.net 下载的，用于将 PDF 页面转换为图像。
I want to Convert 46_2.pdfPDF file to image . The converted 46_2.pngimage is small with dimensions 612 x 792 [ width x height ],
我想将46_2.pdfPDF 文件转换为 image 。转换后的46_2.png图像尺寸小612 x 792 [ width x height ]，
So I want to increase the image dimensions to 1200 x 1400 [ width x height].
所以我想将图像尺寸增加到1200 x 1400 [ width x height].
I tried previously PdfBoxfor converting PDF page into PNG image file. There is a problem only page is converted but text is missing. So I tried PdfRendererlibrary for image conversion.
我以前尝试过PdfBox将 PDF 页面转换为 PNG 图像文件。有问题only page is converted but text is missing。所以我尝试了PdfRenderer库进行图像转换。
Code:
代码：
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();
}
}
}
采纳答案by UdayKiran Pulipati
Convert the selected pageNumberfrom PDF File 46_2.pdf into image format 46_2.pngwith the desired dimensions. Resolution of image is increased with desired dimensions.
将所选pageNumber的 PDF 文件46_2.pdf转换为具有所需尺寸的图像格式46_2.png。图像的分辨率随着所需尺寸的增加而增加。
How to Convert Single PDF page to png or jpeg image format with resolution.
如何将单个 PDF 页面转换为具有分辨率的 png 或 jpeg 图像格式。
Code:
代码：
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();
}
}
}
OutPut:Converted files are saved in C:\PDFCopy\ConvertedFolder. Below one is Console output.
OutPut：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
Thanks Jeff Friesenbased on your exampleof jRebel I tried it in pdfrenderer
感谢Jeff Friesen基于您的 jRebel示例，我在 pdfrenderer 中尝试过
Another Solution:
另一个解决方案：
How to Convert All PDF pages into png / jpeg / jpg/ gif/ bmp image format with resoultion in java using PDF renderer. File to be converted 04-Request-Headers.pdf
如何使用 PDF 渲染器在 java 中将所有 PDF 页面转换为 png/jpeg/jpg/gif/bmp 图像格式。要转换的文件04-Request-Headers.pdf
Code:
代码：
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();
}
}
}
OutPut:All the files are saved in C:/Documents/Converted/Folder. Below one is Console output
OutPut：所有文件都保存在C:/Documents/Converted/文件夹中。下面一个是控制台输出
Total Pages: 13
04-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
