Java实现将txt/word/pdf转成图片并在线预览的功能

2023-05-30 10:38:45 作者：知北游z

本文将基于aspose-words（用于txt、word转图片），pdfbox（用于pdf转图片），封装成一个工具类来实现txt、word、pdf等文件转图片的需求并实现在线预览功能，需要的可以参考一下

如果不想网页上的文章被复制（没错，说的就是某点），如果想实现文档不需要下载下来就能在线预览查看（常见于文档付费下载网站、邮箱附件预览），该怎么做？常见的做法就是将他们转化成图片。以下代码基于 aspose-words（用于txt、word转图片），pdfbox（用于pdf转图片），封装成一个工具类来实现txt、word、pdf等文件转图片的需求。

首先在项目的pom文件里添加下面两个依赖

<dependency>    
    <groupId>com.luhuiguo</groupId>    
    <artifactId>aspose-words</artifactId>    
    <version>23.1</version></dependency>
<dependency>    
    <groupId>org.apache.pdfbox</groupId>    
    <artifactId>pdfbox</artifactId>    
    <version>2.0.4</version>
</dependency>

一、将文件转换成图片，并生成到本地

1、将word文件转成图片

public static void wordToImage(String wordPath, String imagePath) throws Exception {
        Document doc = new Document(wordPath);
        File file = new File(wordPath);
        String filename = file.getName();
        String pathPre = imagePath + File.separator + filename.substring(0, filename.lastIndexOf("."));
        for (int i = 0; i < doc.getPageCount(); i++) {
            Document extractedPage = doc.extractPages(i, 1);
            String path = pathPre + (i + 1) + ".png";
            extractedPage.save(path, SaveFormat.PNG);
        }
    }

验证：

public static void main(String[] args) throws Exception {
        FileConvertUtil.wordToImage("D:\\书籍\\电子书\\其它\\《山海经》异兽图.doc", "D:\\test\\word");
    }

验证结果：

2、将txt文件转成图片（同word文件转成图片）

public static void txtToImage(String txtPath, String imagePath) throws Exception {
        wordToImage(txtPath, imagePath);
    }

验证：

public static void main(String[] args) throws Exception {
        FileConvertUtil.wordToImage("D:\\书籍\\电子书\\其它\\《山海经》异兽图.doc", "D:\\test\\word");
    }

验证结果：

3、将pdf文件转图片

public static void pdfToImage(String pdfPath, String imagePath) throws Exception {
        File file = new File(pdfPath);
        String filename = file.getName();
        String pathPre = imagePath + File.separator + filename.substring(0, filename.lastIndexOf("."));
        PDDocument doc = PDDocument.load(file);
        PDFRenderer renderer = new PDFRenderer(doc);
        for (int i = 0; i < doc.getNumberOfPages(); i++) {
            BufferedImage image = renderer.renderImageWithDPI(i, 144); // Windows native DPI
            String pathname = pathPre + (i + 1) + ".png";
            ImageIO.write(image, "PNG", new File(pathname));
        }
        doc.close();
    }

验证：

public static void main(String[] args) throws Exception {
        FileConvertUtil.pdfToImage("D:\\书籍\\电子书\\其它\\自然哲学的数学原理.pdf", "D:\\test\\pdf");
    }

验证结果：

4、同时支持多种文件类型转成图片

 public static void fileToImage(String sourceFilePath, String imagePath) throws Exception {
        String ext = sourceFilePath.substring(sourceFilePath.lastIndexOf("."));
        switch (ext) {
            case ".doc":
            case ".docx":
                wordToImage(sourceFilePath, imagePath);
                break;
            case ".pdf":
                pdfToImage(sourceFilePath, imagePath);
                break;
            case ".txt":
                txtToImage(sourceFilePath, imagePath);
                break;
            default:
                System.out.println("文件格式不支持");
        }
    }

二、利用多线程提升文件写入本地的效率

在将牛顿大大的长达669页的巨作《自然哲学的数学原理》时发现执行时间较长，执行花了140,281ms。但其实这种IO密集型的操作是通过使用多线程的方式来提升效率的，于是针对这点，我又写了一版多线程的版本。

同步执行导出自然哲学的数学原理.pdf 耗时：

优化后的代码如下：

public static void pdfToImageAsync(String pdfPath, String imagePath) throws Exception {
        long old = System.currentTimeMillis();
        File file = new File(pdfPath);
        PDDocument doc = PDDocument.load(file);
        PDFRenderer renderer = new PDFRenderer(doc);
        int pageCount = doc.getNumberOfPages();
        int numCores = Runtime.getRuntime().availableProcessors();
        ExecutorService executorService = Executors.newFixedThreadPool(numCores);
        for (int i = 0; i < pageCount; i++) {
            int finalI = i;
            executorService.submit(() -> {
                try {
                    BufferedImage image = renderer.renderImageWithDPI(finalI, 144); // Windows native DPI
                    String filename = file.getName();
                    filename = filename.substring(0, filename.lastIndexOf("."));
                    String pathname = imagePath + File.separator + filename + (finalI + 1) + ".png";
                    ImageIO.write(image, "PNG", new File(pathname));
                } catch (Exception ex) {
                    ex.printStackTrace();
                }
            });
        }
        executorService.shutdown();
        executorService.awaitTermination(Long.MAX_VALUE, TimeUnit.NANOSECONDS);
        doc.close();
        long now = System.currentTimeMillis();
        System.out.println("pdfToImage 多线程 转换完成..用时：" + (now - old) + "ms");
    }

多线程执行导出自然哲学的数学原理.pdf 耗时如下：

从上图可以看到本次执行只花了24045ms，只花了原先差不多六分之一的时间，极大地提升了执行效率。除了pdf，word、txt转图片也可以做这样的多线程改造：

//将word转成图片(多线程)
    public static void wordToImageAsync(String wordPath, String imagePath) throws Exception {
        Document doc = new Document(wordPath);
        File file = new File(wordPath);
        String filename = file.getName();
        String pathPre = imagePath + File.separator + filename.substring(0, filename.lastIndexOf("."));
        int numCores = Runtime.getRuntime().availableProcessors();
        ExecutorService executorService = Executors.newFixedThreadPool(numCores);
        for (int i = 0; i < doc.getPageCount(); i++) {
            int finalI = i;
            executorService.submit(() -> {
                try {
                    Document extractedPage = doc.extractPages(finalI, 1);
                    String path = pathPre + (finalI + 1) + ".png";
                    extractedPage.save(path, SaveFormat.PNG);
                } catch (Exception ex) {
                    ex.printStackTrace();
                }
            });
        }
    }
    //将txt转成图片(多线程)
    public static void txtToImageAsync(String txtPath, String imagePath) throws Exception {
        wordToImageAsync(txtPath, imagePath);
    }

三、将文件转换成图片流

有的时候我们转成图片后并不需要在本地生成图片，而是需要将图片返回或者上传到图片服务器，这时候就需要将转换后的图片转成流返回以方便进行传输，代码示例如下：

1、将word文件转成图片流

public static List<byte[]> wordToImageStream(String wordPath) throws Exception {
    Document doc = new Document(wordPath);
    List<byte[]> list = new ArrayList<>();
    for (int i = 0; i < doc.getPageCount(); i++) {
        try(ByteArrayOutputStream outputStream = new ByteArrayOutputStream()){
            Document extractedPage = doc.extractPages(i, 1);
            extractedPage.save(outputStream, SaveFormat.*PNG*);
            list.add(outputStream.toByteArray());
        }
    }
    return list;
}

2、将txt文件转成图片流

public static List<byte[]> txtToImageStream(String txtPath) throws Exception {
    return *wordToImagetream*(txtPath);
}

3、将pdf转成图片流

public static List<byte[]> pdfToImageStream(String pdfPath) throws Exception {
    File file = new File(pdfPath);
    PDDocument doc = PDDocument.*load*(file);
    PDFRenderer renderer = new PDFRenderer(doc);
    List<byte[]> list = new ArrayList<>();
    for (int i = 0; i < doc.getNumberOfPages(); i++) {
        try(ByteArrayOutputStream outputStream = new ByteArrayOutputStream()) {
            BufferedImage image = renderer.renderImageWithDPI(i, 144); // Windows native DPI
            ImageIO.*write*(image, "PNG", outputStream);
            list.add(outputStream.toByteArray());
        }
    }
    doc.close();
    return list;
}

4、支持多种类型文件转成图片流

public static List<byte[]> fileToImageStream(String pdfPath) throws Exception {
    String ext = pdfPath.substring(pdfPath.lastIndexOf("."));
    switch (ext) {
        case ".doc":
        case ".docx":
            return *wordToImageStream*(pdfPath);
        case ".pdf":
            return *pdfToImageStream*(pdfPath);
        case ".txt":
            return *txtToImageStream*(pdfPath);
        default:
            System.*out*.println("文件格式不支持");
    }
    return null;
}

最后附上完整的工具类代码：

package com.fhey.service.common.utils.file;
import com.aspose.words.Document;
import com.aspose.words.SaveFormat;
import com.aspose.words.SaveOptions;
import javassist.bytecode.ByteArray;
import org.apache.pdfbox.pdmodel.PDDocument;
import org.apache.pdfbox.rendering.PDFRenderer;
import javax.imageio.ImageIO;
import java.awt.image.BufferedImage;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
public class FileConvertUtil {
    //文件转成图片
    public static void fileToImage(String sourceFilePath, String imagePath) throws Exception {
        String ext = sourceFilePath.substring(sourceFilePath.lastIndexOf("."));
        switch (ext) {
            case ".doc":
            case ".docx":
                wordToImage(sourceFilePath, imagePath);
                break;
            case ".pdf":
                pdfToImage(sourceFilePath, imagePath);
                break;
            case ".txt":
                txtToImage(sourceFilePath, imagePath);
                break;
            default:
                System.out.println("文件格式不支持");
        }
    }
    //将pdf转成图片
    public static void pdfToImage(String pdfPath, String imagePath) throws Exception {
        File file = new File(pdfPath);
        String filename = file.getName();
        String pathPre = imagePath + File.separator + filename.substring(0, filename.lastIndexOf("."));
        PDDocument doc = PDDocument.load(file);
        PDFRenderer renderer = new PDFRenderer(doc);
        for (int i = 0; i < doc.getNumberOfPages(); i++) {
            BufferedImage image = renderer.renderImageWithDPI(i, 144); // Windows native DPI
            String pathname = pathPre + (i + 1) + ".png";
            ImageIO.write(image, "PNG", new File(pathname));
        }
        doc.close();
    }
    //txt转成转成图片
    public static void txtToImage(String txtPath, String imagePath) throws Exception {
        wordToImage(txtPath, imagePath);
    }
    //将word转成图片
    public static void wordToImage(String wordPath, String imagePath) throws Exception {
        Document doc = new Document(wordPath);
        File file = new File(wordPath);
        String filename = file.getName();
        String pathPre = imagePath + File.separator + filename.substring(0, filename.lastIndexOf("."));
        for (int i = 0; i < doc.getPageCount(); i++) {
            Document extractedPage = doc.extractPages(i, 1);
            String path = pathPre + (i + 1) + ".png";
            extractedPage.save(path, SaveFormat.PNG);
        }
    }
    //pdf转成图片(多线程)
    public static void pdfToImageAsync(String pdfPath, String imagePath) throws Exception {
        long old = System.currentTimeMillis();
        File file = new File(pdfPath);
        PDDocument doc = PDDocument.load(file);
        PDFRenderer renderer = new PDFRenderer(doc);
        int pageCount = doc.getNumberOfPages();
        int numCores = Runtime.getRuntime().availableProcessors();
        ExecutorService executorService = Executors.newFixedThreadPool(numCores);
        for (int i = 0; i < pageCount; i++) {
            int finalI = i;
            executorService.submit(() -> {
                try {
                    BufferedImage image = renderer.renderImageWithDPI(finalI, 144); // Windows native DPI
                    String filename = file.getName();
                    filename = filename.substring(0, filename.lastIndexOf("."));
                    String pathname = imagePath + File.separator + filename + (finalI + 1) + ".png";
                    ImageIO.write(image, "PNG", new File(pathname));
                } catch (Exception ex) {
                    ex.printStackTrace();
                }
            });
        }
        executorService.shutdown();
        executorService.awaitTermination(Long.MAX_VALUE, TimeUnit.NANOSECONDS);
        doc.close();
        long now = System.currentTimeMillis();
        System.out.println("pdfToImage 多线程 转换完成..用时：" + (now - old) + "ms");
    }
    //将word转成图片(多线程)
    public static void wordToImageAsync(String wordPath, String imagePath) throws Exception {
        Document doc = new Document(wordPath);
        File file = new File(wordPath);
        String filename = file.getName();
        String pathPre = imagePath + File.separator + filename.substring(0, filename.lastIndexOf("."));
        int numCores = Runtime.getRuntime().availableProcessors();
        ExecutorService executorService = Executors.newFixedThreadPool(numCores);
        for (int i = 0; i < doc.getPageCount(); i++) {
            int finalI = i;
            executorService.submit(() -> {
                try {
                    Document extractedPage = doc.extractPages(finalI, 1);
                    String path = pathPre + (finalI + 1) + ".png";
                    extractedPage.save(path, SaveFormat.PNG);
                } catch (Exception ex) {
                    ex.printStackTrace();
                }
            });
        }
    }
    //将txt转成图片(多线程)
    public static void txtToImageAsync(String txtPath, String imagePath) throws Exception {
        wordToImageAsync(txtPath, imagePath);
    }
    //将文件转成图片流
    public static List<byte[]> fileToImageStream(String pdfPath) throws Exception {
        String ext = pdfPath.substring(pdfPath.lastIndexOf("."));
        switch (ext) {
            case ".doc":
            case ".docx":
                return wordToImageStream(pdfPath);
            case ".pdf":
                return pdfToImageStream(pdfPath);
            case ".txt":
                return txtToImageStream(pdfPath);
            default:
                System.out.println("文件格式不支持");
        }
        return null;
    }
    //将pdf转成图片流
    public static List<byte[]> pdfToImageStream(String pdfPath) throws Exception {
        File file = new File(pdfPath);
        PDDocument doc = PDDocument.load(file);
        PDFRenderer renderer = new PDFRenderer(doc);
        List<byte[]> list = new ArrayList<>();
        for (int i = 0; i < doc.getNumberOfPages(); i++) {
            try(ByteArrayOutputStream outputStream = new ByteArrayOutputStream()) {
                BufferedImage image = renderer.renderImageWithDPI(i, 144); // Windows native DPI
                ImageIO.write(image, "PNG", outputStream);
                list.add(outputStream.toByteArray());
            }
        }
        doc.close();
        return list;
    }
    //将word转成图片流
    public static List<byte[]> wordToImageStream(String wordPath) throws Exception {
        Document doc = new Document(wordPath);
        List<byte[]> list = new ArrayList<>();
        for (int i = 0; i < doc.getPageCount(); i++) {
            try(ByteArrayOutputStream outputStream = new ByteArrayOutputStream()){
                Document extractedPage = doc.extractPages(i, 1);
                extractedPage.save(outputStream, SaveFormat.PNG);
                list.add(outputStream.toByteArray());
            }
        }
        return list;
    }
    //将txt转成图片流
    public static List<byte[]> txtToImageStream(String txtPath) throws Exception {
        return wordToImageStream(txtPath);
    }
}

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Java实现将txt/word/pdf转成图片并在线预览的功能

一、将文件转换成图片，并生成到本地

1、将word文件转成图片

2、将txt文件转成图片（同word文件转成图片）

3、将pdf文件转图片

4、同时支持多种文件类型转成图片

二、利用多线程提升文件写入本地的效率

三、将文件转换成图片流

1、将word文件转成图片流

2、将txt文件转成图片流

3、将pdf转成图片流

4、支持多种类型文件转成图片流

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