我正在尝试将一组 PDF 合并在一起,并确保它们被很好地压缩,并且没有重复的资源。但是,在我的代码中,如果我在编写器上调用 SetSmartMode(true),第一次写入它总是会导致 NullReferenceException。
这是我的(vb.net)代码:
Private Function CombinePdfBatch(pdfMetaData As IEnumerable(Of QuestDataSet.MetaDataRow), batchNumber As Integer,
fileNamePrefix As String, outputDir As String) As String
Dim outputFileName As String = Path.Combine(outputDir, fileNamePrefix & "_" & batchNumber & ".pdf")
Using combinedPdf As New PdfDocument(New PdfWriter(Path.Combine(outputDir, fileNamePrefix & "_" & batchNumber & ".pdf")).SetSmartMode(True))
'Make sure we close the underlying stream when we're done with the combination
combinedPdf.SetCloseWriter(True)
combinedPdf.SetCloseReader(False)
combinedPdf.SetFlushUnusedObjects(False)
combinedPdf.GetWriter().SetCompressionLevel(CompressionConstants.BEST_COMPRESSION)
combinedPdf.GetWriter().SetCloseStream(True)
combinedPdf.SetDefaultPageSize(New Geom.PageSize(630, 810))
Dim merger As New PdfMerger(combinedPdf)
For Each currentMD As QuestDataSet.MetaDataRow In pdfMetaData
Using currentPDF As New PdfDocument(New PdfReader(Path.Combine(programPaths.Input, currentMD.ReceivedFilesRowByInputFileRelation.FileName)))
currentPDF.SetCloseReader(True)
currentPDF.SetCloseWriter(False)
currentPDF.GetReader().SetCloseStream(True)
currentMD.CombinedFileName = outputFileName
currentMD.StartPage = combinedPdf.GetNumberOfPages() + 1
merger.Merge(currentPDF, 1, currentPDF.GetNumberOfPages())
currentMD.EndPage = combinedPdf.GetNumberOfPages()
End Using
Next
merger.Close()
End Using
Return outputFileName
End Function
一旦merger.Merge
被调用,NullReferenceException
就会抛出 a。我已经用许多其他功能替换了它,但是如果在编写器处于智能模式时将任何内容添加到 PDF 中,它就会崩溃。
如果我禁用智能模式,PDF 将被合并。但我需要在不牺牲太多质量的情况下尽可能减小这些 PDF 的大小。因为我知道它们都使用相同的字体并共享一些库存图像,所以我想我会将它们全部组合起来。
编辑:这是一个堆栈跟踪,因为我爱你们:
System.NullReferenceException occurred
HResult=-2147467261
Message=Object reference not set to an instance of an object.
Source=itext.kernel
StackTrace:
at iText.Kernel.Pdf.PdfWriter.ByteStore.SerDic(PdfDictionary dic, Int32 level, ByteBufferOutputStream bb, IntHashtable serialized)
at iText.Kernel.Pdf.PdfWriter.ByteStore.SerObject(PdfObject obj, Int32 level, ByteBufferOutputStream bb, IntHashtable serialized)
at iText.Kernel.Pdf.PdfWriter.ByteStore..ctor(PdfStream str, IntHashtable serialized)
at iText.Kernel.Pdf.PdfWriter.SmartCopyObject(PdfObject obj)
at iText.Kernel.Pdf.PdfWriter.CopyObject(PdfObject obj, PdfDocument document, Boolean allowDuplicating)
at iText.Kernel.Pdf.PdfObject.ProcessCopying(PdfDocument documentTo, Boolean allowDuplicating)
at iText.Kernel.Pdf.PdfArray.CopyContent(PdfObject from, PdfDocument document)
at iText.Kernel.Pdf.PdfWriter.CopyObject(PdfObject obj, PdfDocument document, Boolean allowDuplicating)
at iText.Kernel.Pdf.PdfObject.ProcessCopying(PdfDocument documentTo, Boolean allowDuplicating)
at iText.Kernel.Pdf.PdfDictionary.CopyContent(PdfObject from, PdfDocument document)
at iText.Kernel.Pdf.PdfWriter.CopyObject(PdfObject obj, PdfDocument document, Boolean allowDuplicating)
at iText.Kernel.Pdf.PdfObject.ProcessCopying(PdfDocument documentTo, Boolean allowDuplicating)
at iText.Kernel.Pdf.PdfObject.CopyTo(PdfDocument document, Boolean allowDuplicating)
at iText.Kernel.Pdf.PdfDictionary.CopyTo(PdfDocument document, Boolean allowDuplicating)
at iText.Kernel.Pdf.PdfDictionary.CopyTo(PdfDocument document, IList`1 excludeKeys, Boolean allowDuplicating)
at iText.Kernel.Pdf.PdfPage.CopyTo(PdfDocument toDocument, IPdfPageExtraCopier copier)
at iText.Kernel.Pdf.PdfDocument.CopyPagesTo(IList`1 pagesToCopy, PdfDocument toDocument, Int32 insertBeforePage, IPdfPageExtraCopier copier)
at iText.Kernel.Pdf.PdfDocument.CopyPagesTo(IList`1 pagesToCopy, PdfDocument toDocument, IPdfPageExtraCopier copier)
at iText.Kernel.Pdf.PdfDocument.CopyPagesTo(IList`1 pagesToCopy, PdfDocument toDocument)
at iText.Kernel.Utils.PdfMerger.Merge(PdfDocument from, IList`1 pages)
at iText.Kernel.Utils.PdfMerger.Merge(PdfDocument from, Int32 fromPage, Int32 toPage)
at QuestMonolithic.Process.CombinePdfBatch(IEnumerable`1 pdfMetaData, Int32 batchNumber, String fileNamePrefix, String outputDir) in C:\Users\cchrist\Documents\Visual Studio 2012\Projects\Quest_Monolithic\trunk\source\Process.vb:line 594
InnerException: