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📜  PDFBox获取位置和图像大小

📅  最后修改于: 2021-01-07 07:45:49             🧑  作者: Mango

获取图像的位置和大小

在本教程中，我们将学习如何从所有页面获取PDF中图像的坐标或位置以及大小。这可以通过使用PDFStreamEngine类执行。此类通过提供回调接口来处理和执行处理PDF文档的操作。

为了获取PDF文档中图像的位置和大小，我们将扩展PDFStreamEngine类并拦截并实现processOperator()方法。

对于PDF文档中的每个对象，我们将检查该对象是否为图像对象，并获取其属性，例如(X，Y)坐标和大小。为此，我们可以使用在PDFStreamEngine.processPage(page)中调用的processOperator()方法。

请按照以下步骤获取现有PDF文档中图像的坐标或位置以及尺寸，

扩展PDFStreamEngine

在此，我们必须首先创建一个Java类，并使用PDFStreamEngine对其进行扩展。可以在下面的代码中显示。

publicclass GetImageLocationsAndSize extends PDFStreamEngine {

......

}

调用processPage()

对于PDF文档中的每个页面，调用方法processPage() 。此方法接受页面名称作为参数。可以在以下代码中显示。

for( PDPage page : document.getPages() )
                {
    pageNum++;
    printer.processPage(page);
                }

覆盖processOperator()

对于PDF页面中的每个对象，在processPage()方法中调用processOperator。我们还可以覆盖processOperator()方法。

@Override
protectedvoid processOperator( Operator operator, Listoperands)
 throws IOException { 

...........

}

检查图像

现在，我们可以检查已发送到processOperator()方法的对象是否为图像对象。

if( xobjectinstanceof PDImageXObject)
            {
                PDImageXObject image = (PDImageXObject)xobject;
    intimageWidth = image.getWidth();
    intimageHeight = image.getHeight();                
                System.out.println("\nImage [" + objectName.getName() + "]");
              }

打印位置和尺寸

最后，如果给定的对象是图像对象，则print图像的位置和大小。

             // position of image in the PDF in terms of user space units
              System.out.println("Position in PDF = " + ctmNew.getTranslateX() + ",
              " + ctmNew.getTranslateY() + " in user space units");
    
// raw size in pixels
              System.out.println("Raw image size  = " + imageWidth + ",
              " + imageHeight + " in pixels");

    // displayed size in user space units
              System.out.println("Displayed size  = " + imageXScale + ",
              " + imageYScale + " in user space units");

例-

import org.apache.pdfbox.cos.COSBase;
import org.apache.pdfbox.cos.COSName;
import org.apache.pdfbox.pdmodel.PDDocument;
import org.apache.pdfbox.pdmodel.PDPage;
import org.apache.pdfbox.pdmodel.graphics.PDXObject;
import org.apache.pdfbox.pdmodel.graphics.form.PDFormXObject;
import org.apache.pdfbox.pdmodel.graphics.image.PDImageXObject;
import org.apache.pdfbox.util.Matrix;
import org.apache.pdfbox.contentstream.operator.DrawObject;
import org.apache.pdfbox.contentstream.operator.Operator;
import org.apache.pdfbox.contentstream.PDFStreamEngine;

import java.io.File;
import java.io.IOException;
import java.util.List;

import org.apache.pdfbox.contentstream.operator.state.Concatenate;
import org.apache.pdfbox.contentstream.operator.state.Restore;
import org.apache.pdfbox.contentstream.operator.state.Save;
import org.apache.pdfbox.contentstream.operator.state.SetGraphicsStateParameters;
import org.apache.pdfbox.contentstream.operator.state.SetMatrix;

public class GetImageLocationsAndSize extends PDFStreamEngine {    

public void GetImageLocationsAndSize() throws IOException
    {
// preparing PDFStreamEngine
        addOperator(new Concatenate());
        addOperator(new DrawObject());
        addOperator(new SetGraphicsStateParameters());
        addOperator(new Save());
        addOperator(new Restore());
        addOperator(new SetMatrix());
    }    
        publicstaticvoid main(String[] args)throws IOException {
                    
        PDDocument document = null;
          String fileName = "/eclipse-workspace/Merge.pdf";
    try
          {
    document = PDDocument.load( new File(fileName) );
             GetImageLocationsAndSize printer = new GetImageLocationsAndSize();
    intpageNum = 0;
    for( PDPage page : document.getPages() )
                {
    pageNum++;
                    System.out.println( "\n\nProcessing PDF page:
                    " + pageNum +"\n---------------------------------");
    printer.processPage(page);
                }
            }
    finally
            {
    if( document != null )
                {
    document.close();
                }
            }
        }
    
    protectedvoid processOperator( Operator operator, Listoperands)
    throws IOException
        {
            String operation = operator.getName();
    if( "Do".equals(operation) )
            {
                COSName objectName = (COSName) operands.get( 0 );
    // get the PDF object
                PDXObject xobject = getResources().getXObject( objectName );

    // check if the object is an image object
    if( xobjectinstanceof PDImageXObject)
                {
                    PDImageXObject image = (PDImageXObject)xobject;
    intimageWidth = image.getWidth();
    intimageHeight = image.getHeight();
    
                  System.out.println("\nImage [" + objectName.getName() + "]");
    
           Matrix ctmNew = getGraphicsState().getCurrentTransformationMatrix();
    floatimageXScale = ctmNew.getScalingFactorX();
    floatimageYScale = ctmNew.getScalingFactorY();
    
    // position of image in the PDF in terms of user space units
               System.out.println("position in PDF = " + ctmNew.getTranslateX() + ",
               " + ctmNew.getTranslateY() + " in user space units");
    
// raw size in pixels
               System.out.println("raw image size  = " + imageWidth + ",
               " + imageHeight + " in pixels");

    // displayed size in user space units
               System.out.println("displayed size  = " + imageXScale + ",
               " + imageYScale + " in user space units");

                }
    elseif(xobjectinstanceof PDFormXObject)
                {
                    PDFormXObject form = (PDFormXObject)xobject;
                    showForm(form);
                }
            }
    else
            {
    super.processOperator( operator, operands );
            }
     }
}

输出：