使用iText PDF删除PDF中页眉和页脚的问题

Question

我使用itext-xtra-5.5.6 api来删除/清理页眉和页脚。

这是代码

//removes header and footer based on the configuration
public static void cleanUpContent(String inPDFFile,String targetPDFFile,PDFConfig pdfConfig) throws Exception{
    PdfReader reader = new PdfReader(inPDFFile);
    OutputStream outputStream = new FileOutputStream(targetPDFFile);
    float upperY=pdfConfig.getPdfUpperY();
    float lowerY=pdfConfig.getPdfLowerY();
    boolean highLightColor=pdfConfig.isPdfHighLightClippedTextColor();
    PdfStamper stamper = new PdfStamper(reader, outputStream);
    List<PdfCleanUpLocation> cleanUpLocations = new ArrayList<PdfCleanUpLocation>();

    for (int i = 1; i <= reader.getNumberOfPages(); i++) {
        Rectangle pageRect = reader.getCropBox(i);  
        Rectangle headerRect= new Rectangle(pageRect);
        headerRect.setBottom(headerRect.getTop()-upperY);               
        Rectangle footerRect= new Rectangle(pageRect);
        footerRect.setTop(footerRect.getBottom()+lowerY);   

        if(highLightColor){
            cleanUpLocations.add(new PdfCleanUpLocation(i, headerRect,BaseColor.GREEN));
            cleanUpLocations.add(new PdfCleanUpLocation(i, footerRect,BaseColor.GREEN));
        }else{
            cleanUpLocations.add(new PdfCleanUpLocation(i, headerRect));
            cleanUpLocations.add(new PdfCleanUpLocation(i, footerRect));
        }
    }   
    PdfCleanUpProcessor cleaner = new PdfCleanUpProcessor(cleanUpLocations, stamper);
    try{
        cleaner.cleanUp();
    }catch(Exception e){
         e.printStackTrace();
    }

    stamper.close();
    reader.close();
    outputStream.flush();
    outputStream.close();
}

当我运行代码以删除包含1440页，其中up​​perY = 65且lowerY = 65的PDF文件的页眉和页脚时，代码将删除页面中的所有内容，但是当upperY = 65且lowerY = 45时代码正在删除预期的页眉和页脚。

另一个问题是DefaultClipper类

中某些页面的Null指针异常

private void fixupFirstLefts2( OutRec OldOutRec, OutRec NewOutRec ) {
    for (final OutRec outRec : polyOuts) {
        if (outRec.firstLeft.equals( OldOutRec )) {
            outRec.firstLeft = NewOutRec;
        }
    }
}

polyOuts中的

- ＆gt; outRec.firstLeft为null，因此outRec.firstLeft.equals方法抛出Null指针异常。

异常堆栈跟踪

java.lang.NullPointerException
    at com.itextpdf.text.pdf.parser.clipper.DefaultClipper.fixupFirstLefts2(DefaultClipper.java:1463)
    at com.itextpdf.text.pdf.parser.clipper.DefaultClipper.joinCommonEdges(DefaultClipper.java:2121)
    at com.itextpdf.text.pdf.parser.clipper.DefaultClipper.executeInternal(DefaultClipper.java:1420)
    at com.itextpdf.text.pdf.parser.clipper.DefaultClipper.execute(DefaultClipper.java:1362)
    at com.itextpdf.text.pdf.pdfcleanup.PdfCleanUpRegionFilter.filterFillPath(PdfCleanUpRegionFilter.java:174)
    at com.itextpdf.text.pdf.pdfcleanup.PdfCleanUpRenderListener.filterCurrentPath(PdfCleanUpRenderListener.java:402)
    at com.itextpdf.text.pdf.pdfcleanup.PdfCleanUpRenderListener.renderPath(PdfCleanUpRenderListener.java:232)
    at com.itextpdf.text.pdf.parser.PdfContentStreamProcessor.paintPath(PdfContentStreamProcessor.java:377)
    at com.itextpdf.text.pdf.parser.PdfContentStreamProcessor.access$6300(PdfContentStreamProcessor.java:60)
    at com.itextpdf.text.pdf.parser.PdfContentStreamProcessor$PaintPath.invoke(PdfContentStreamProcessor.java:1183)
    at com.itextpdf.text.pdf.pdfcleanup.PdfCleanUpContentOperator.invoke(PdfCleanUpContentOperator.java:138)
    at com.itextpdf.text.pdf.parser.PdfContentStreamProcessor.invokeOperator(PdfContentStreamProcessor.java:286)
    at com.itextpdf.text.pdf.parser.PdfContentStreamProcessor.processContent(PdfContentStreamProcessor.java:429)
    at com.itextpdf.text.pdf.parser.PdfContentStreamProcessor$FormXObjectDoHandler.handleXObject(PdfContentStreamProcessor.java:1252)
    at com.itextpdf.text.pdf.parser.PdfContentStreamProcessor.displayXObject(PdfContentStreamProcessor.java:352)
    at com.itextpdf.text.pdf.parser.PdfContentStreamProcessor.access$6100(PdfContentStreamProcessor.java:60)
    at com.itextpdf.text.pdf.parser.PdfContentStreamProcessor$Do.invoke(PdfContentStreamProcessor.java:988)
    at com.itextpdf.text.pdf.pdfcleanup.PdfCleanUpContentOperator.invoke(PdfCleanUpContentOperator.java:138)
    at com.itextpdf.text.pdf.parser.PdfContentStreamProcessor.invokeOperator(PdfContentStreamProcessor.java:286)
    at com.itextpdf.text.pdf.parser.PdfContentStreamProcessor.processContent(PdfContentStreamProcessor.java:429)
    at com.itextpdf.text.pdf.pdfcleanup.PdfCleanUpProcessor.cleanUpPage(PdfCleanUpProcessor.java:160)
    at com.itextpdf.text.pdf.pdfcleanup.PdfCleanUpProcessor.cleanUp(PdfCleanUpProcessor.java:135)

不确定我在哪里做错了。我甚至试图查看pdf页面是否包含图像或其他类型，但页面只是基于文本。请帮助解决2个问题。