如何用Java和PDFBox从PDF中裁剪,分裂,删除页面
#编程 #java #pdf #pdfbox

用Maven创建一个新的Java项目

让我们从创建一个新的Java项目,名为 pdf_utils ,使用maven:

mvn archetype:generate \
    -DgroupId=com.pdf.pdf_utils \
    -DartifactId=pdf_utils \
    -DarchetypeArtifactId=maven-archetype-quickstart \
    -DarchetypeVersion=1.4 \
    -DinteractiveMode=false

然后,打开 pdf_utils/pom.xml file,并在依赖项中添加依赖项 e节:

<dependencies>
   ...
    <dependency>
      <groupId>org.apache.pdfbox</groupId>
      <artifactId>pdfbox</artifactId>
      <version>2.0.27</version>
    </dependency>
    ...
</dependencies>

还更改目标和源编译器版本:

 <plugins>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-compiler-plugin</artifactId>
        <configuration>
          <source>17</source>
          <target>17</target>
        </configuration>
      </plugin>
</plugins>

然后将生成的 src/main/java/com/pdf/pdf/pdf_utils/app.java 类重命名为 pdfutils

如何裁剪PDF

现在,我们将开发一个Java功能,该功能在PDF文档中的每个页面上播种,并将裁剪的内容保存在新的PDF文件中。以毫米为单位指定的裁剪坐标将作为功能的输入。

  1. 添加辅助功能以在MM <->单位之间转换
  2. 将MM转换为单位
  3. 提取文档的文件名
  4. 裁剪每页
  5. 保存结果&附加“ - 编写”到Ouyput文件的名称
public String cropPDFMM(float x, float y, float width, float height, String srcFilePath) throws IOException {
    // helper functions to convert between mm <-> units
    Function<Float, Float> mmToUnits = (Float a) -> a / 0.352778f;
    Function<Float, Float> unitsToMm = (Float a) -> a * 0.352778f;

    // convert mm to units
    float xUnits = mmToUnits.apply(x);
    float yUnits = mmToUnits.apply(y);
    float widthUnits = mmToUnits.apply(width);
    float heightUnits = mmToUnits.apply(height);

    // extract the doc's file name
    File srcFile = new File(srcFilePath);
    String fileName = srcFile.getName();
    int dotIndex = fileName.lastIndexOf('.');
    String fileNameWithoutExtension =  (dotIndex == -1) ? fileName : fileName.substring(0, dotIndex);

    // crop each page
    PDDocument doc = PDDocument.load(srcFile);
    int nrOfPages = doc.getNumberOfPages();
    PDRectangle newBox = new PDRectangle(
            xUnits,
            yUnits,
            widthUnits,
            heightUnits);
    for (int i = 0; i < nrOfPages; i++) {
        doc.getPage(i).setCropBox(newBox);
    }

    // save the result & append -cropped to the file name
    File outFile = new File(fileNameWithoutExtension + "-cropped.pdf");
    doc.save(outFile);
    doc.close();
    return outFile.getCanonicalPath();
}

让我们测试 croppdfmm 通过从 main 函数中调用它:

public static void main( String[] args )
    {
    String srcFilePath = "/Users/user/.../file.pdf";
    PDFUtils app = new PDFUtils();

    try {
        ///// crop pdf
        float x = 18f;
        float y = 20f;
        float width = 140f;
        float height = 210f;
        String resultFilePath = app.cropPDFMM(x, y, width, height, srcFilePath);

        System.out.println( "Done!" );
    } catch (Exception e) {
        System.out.println(e);
    }
}

您应该在当前目录中看到一个名为 file-cropped.pdf 的文件。

如何从PDF中删除页面

要从文档中删除特定页面,我们可以使用一系列整数范围。每个范围都由一个开始页面和一个末端页面组成([startpage1,endPage1,startpage2,endpage2,...])。该函数通过文档的每个页面迭代,并检查页码是否不在数组中的任何指定范围之外。如果页面不在任何范围内,则将其附加到新文档中。

  1. 添加辅助功能以测试页面是否在范围内
  2. 测试每个页码 - >将其附加到临时性。 Doc
  3. 保存温度。 Doc。 - >覆盖输入文件
public void removePages(String srcFilePath, Integer[] pageRanges) throws IOException {
     // a helper function to test if a page is within a range
     BiPredicate<Integer, Integer[]> pageInInterval = (Integer page, Integer[] allPages) -> {
         for (int j = 0; j < allPages.length; j+=2) {
             int startPage = allPages[j];
             int endPage = allPages[j+1];
             if (page >= startPage-1 && page < endPage) {
                 return true;
             }
         }
         return false;
     };

     File srcFile = new File(srcFilePath);
     PDDocument pdfDocument = PDDocument.load(srcFile);
     PDDocument tmpDoc = new PDDocument();

     // test if a page is within a range
     // if not, append the page to a temp. doc.
     for (int i = 0; i < pdfDocument.getNumberOfPages(); i++) {
         if (pageInInterval.test(i, pageRanges)) {
             continue;
         }
         tmpDoc.addPage(pdfDocument.getPage(i));
     }

     // save the temporary doc.
     tmpDoc.save(new File(srcFilePath));
     tmpDoc.close();
     pdfDocument.close();
 }

让我们通过在主要功能中调用 emovepages 来对其进行测试:

 ///// remove pages
app.removePages(resultFilePath, new Integer[] {1, 21, 376, 428});

它将覆盖输入(裁剪)文件。

如何拆分PDF

现在,我们将引入一个函数,该函数可以将PDF拆分为多个单独的PDF,每个结果文件包含指定数量的页面。该功能期望两个输入:源PDF文档的路径和每个拆分文件中所需的页面数。

  1. 提取源文件的名称
  2. 对于每个nrofpages
  3. 将它们附加到临时文件
  4. 使用源文件的名称 +索引保存临时文档
public void splitPDF(String srcFilePath, int nrOfPages) throws IOException {
    // extract file's name
    File srcFile = new File(srcFilePath);
    String fileName = srcFile.getName();
    int dotIndex = fileName.lastIndexOf('.');
    String fileNameWithoutExtension =  (dotIndex == -1) ? fileName : fileName.substring(0, dotIndex);

    PDDocument pdfDocument = PDDocument.load(srcFile);

    // extract every nrOfPages to a temporary document
    // append an index to its name and save it
    for (int i = 1; i < pdfDocument.getNumberOfPages(); i+=nrOfPages) {
        Splitter splitter = new Splitter();

        int fromPage = i;
        int toPage = i+nrOfPages;
        splitter.setStartPage(fromPage);
        splitter.setEndPage(toPage);
        splitter.setSplitAtPage(toPage - fromPage );

        List<PDDocument> lst = splitter.split(pdfDocument);

        PDDocument pdfDocPartial = lst.get(0);
        File f = new File(fileNameWithoutExtension + "-" + i + ".pdf");
        pdfDocPartial.save(f);
        pdfDocPartial.close();
    }
    pdfDocument.close();
}

这是完整的 main()函数:

public static void main( String[] args ){
    String srcFilePath = "/Users/user/pdfs/file.pdf";
    PDFUtils app = new PDFUtils();

    try {
         ///// crop pdf
        float x = 18f;
        float y = 20f;
        float width = 140f;
        float height = 210f;
        String resultFilePath = app.cropPDFMM(x, y, width, height, srcFilePath);

        ///// remove pages
        app.removePages(resultFilePath, new Integer[] {1, 21, 376, 428});

        ///// split pages
        app.splitPDF(resultFilePath, 20);

        System.out.println( "Done!" );
    } catch (Exception e) {
        System.out.println(e);
    }
}

合并每张纸2页(2UP)

此功能是从https://stackoverflow.com/questions/12093408/pdfbox-merge-2-portrait-pages-onto-a-single-side-by-side-landscape-page的灵感来源的。

  1. 创建一个临时文档
  2. 迭代原始文档的页面。 - >获取左右页
  3. 创建一个具有正确维度的新“输出”页面
  4. 附加左页(0,0)
  5. 附加右页,翻译为(左页的宽度,0)
  6. 保存温度。 doc->覆盖源文件
public void mergePages(String srcFilePath) throws IOException {

    // SOURCE: https://stackoverflow.com/questions/12093408/pdfbox-merge-2-portrait-pages-onto-a-single-side-by-side-landscape-page
    File srcFile = new File(srcFilePath);
    PDDocument pdfDocument = PDDocument.load(srcFile);
    PDDocument outPdf = new PDDocument();

    for (int i = 0; i < pdfDocument.getNumberOfPages(); i+=2) {
        PDPage page1 = pdfDocument.getPage(i);
        PDPage page2 = pdfDocument.getPage(i+1);
        PDRectangle pdf1Frame = page1.getCropBox();
        PDRectangle pdf2Frame = page2.getCropBox();
        PDRectangle outPdfFrame = new PDRectangle(pdf1Frame.getWidth()+pdf2Frame.getWidth(), Math.max(pdf1Frame.getHeight(), pdf2Frame.getHeight()));

        // Create output page with calculated frame and add it to the document
        COSDictionary dict = new COSDictionary();
        dict.setItem(COSName.TYPE, COSName.PAGE);
        dict.setItem(COSName.MEDIA_BOX, outPdfFrame);
        dict.setItem(COSName.CROP_BOX, outPdfFrame);
        dict.setItem(COSName.ART_BOX, outPdfFrame);
        PDPage newP = new PDPage(dict);
        outPdf.addPage(newP);

        // Source PDF pages has to be imported as form XObjects to be able to insert them at a specific point in the output page
        LayerUtility layerUtility = new LayerUtility(outPdf);
        PDFormXObject formPdf1 = layerUtility.importPageAsForm(pdfDocument, page1);
        PDFormXObject formPdf2 = layerUtility.importPageAsForm(pdfDocument, page2);

        AffineTransform afLeft = new AffineTransform();
        layerUtility.appendFormAsLayer(newP, formPdf1, afLeft, "left" + i);
        AffineTransform afRight = AffineTransform.getTranslateInstance(pdf1Frame.getWidth(), 0.0);
        layerUtility.appendFormAsLayer(newP, formPdf2, afRight, "right" + i);
    }

    outPdf.save(srcFile);
    outPdf.close();
    pdfDocument.close();
}

更新 main()对其进行测试:

...
 ///// 2 pages per sheet
app.mergePages(resultFilePath);
...

这是导入的完整列表:

package com.pdf.pdf_utils;

import org.apache.pdfbox.cos.COSDictionary;
import org.apache.pdfbox.cos.COSName;
import org.apache.pdfbox.multipdf.LayerUtility;
import org.apache.pdfbox.multipdf.Splitter;
import org.apache.pdfbox.pdmodel.PDDocument;
import org.apache.pdfbox.pdmodel.PDPage;
import org.apache.pdfbox.pdmodel.common.PDRectangle;
import org.apache.pdfbox.pdmodel.graphics.form.PDFormXObject;

import java.awt.geom.AffineTransform;
import java.io.File;
import java.io.IOException;
import java.util.List;
import java.util.function.BiPredicate;
import java.util.function.Function;

源代码可用here