文档在线预览（一）通过将txt、word、pdf转成图片实现在线预览功能

雨点打透心脏的1/2处 2024-03-16 15:58 79阅读 0赞

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：

![9cf0954439aa367d49443b28708affd9.png][]

#### 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：

![b2f689a0ad9866f36d633c60a7cc70a7.png][]

#### 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：

![62ab5e23117adea84ebaf22e52d6b990.png][]

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：

![f4ff9ab60cb3b0fdd61514e7b4e5ac95.png][]

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：

![d4fcb4593cc92672c07797b7f5cb695f.png][]

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);
        }
    }

[9cf0954439aa367d49443b28708affd9.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/16/92a9ab2a431a4ab2bfcf29afd81b9b81.png
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