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。 我用过PDFRenderer-0.9.0 jar。 它从java.net下载，用于将PDF页面转换为图像。
我想将46_2.pdf PDF文件转换为图像。 转换后的46_2.png图片很小，尺寸为612 x 792 [ width x height ] ，
所以我想将图像尺寸增加到1200 x 1400 [ width x height] 。
我以前试过PdfBox将PDF页面转换成PNG图像文件。 有一个问题， only page is converted but text is missing 。 所以我尝试了PdfRenderer进行图像转换。
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(); } } }
将所选pageNumber从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。
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：转换后的文件保存在C:\PDFCopy\Converted Folder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中尝试过它
另一种方案：
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
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：所有文件都保存在C:/Documents/Converted/ Folder中。 下面是控制台输出
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