iText 7 - 在PDF上添加和刪除水印

Question

我想使用iText 7添加和刪除水印到PDF上。我能夠添加水印，但無法再將其刪除。我只能找到與iText 5相關的相關代碼/例子。任何指針讚賞，謝謝。

這是我如何添加水印（使用圖層）：

  pdfDoc = new PdfDocument(new PdfReader(sourceFile), new PdfWriter(destinationPath)); 
      var numberOfPages = pdfDoc.GetNumberOfPages(); 

      PageSize ps = pdfDoc.GetDefaultPageSize(); 

      for (var i = 1; i <= numberOfPages; i++) 
      { 
       PdfPage page = pdfDoc.GetPage(i); 
       PdfLayer layer = new PdfLayer("watermark", pdfDoc); 
       var canvas = new PdfCanvas(page); 
       var pageSize = page.GetPageSize(); 
       var paragraph = new Paragraph(message.WatermarkText).SetFontSize(60); 
       paragraph.SetFontColor(Color.BLACK, 0.2f); 

       Canvas canvasModel; 
       canvas.BeginLayer(layer); 
       canvasModel = new Canvas(canvas, pdfDoc, ps); 
       canvasModel.ShowTextAligned(paragraph, pageSize.GetWidth()/2, pageSize.GetHeight()/2, pdfDoc.GetPageNumber(page), TextAlignment.CENTER, VerticalAlignment.MIDDLE, 45); 
       canvasModel.SetFontColor(Color.GREEN, 0.2f); 
       canvas.EndLayer(); 
      } 
      pdfDoc.Close(); 

這是我試圖去除水印。我想徹底刪除它，而不是僅僅設置爲不顯示層（知道的任​​何示例代碼）：

  pdfDoc = new PdfDocument(new PdfReader(sourceFile), new PdfWriter(destinationPath));      
      IList<PdfLayer> layers = pdfDoc.GetCatalog().GetOCProperties(true).GetLayers();    

      for (var i = 0; i <= layers.Count; i++) 
      { 
       var t = layers[i].GetPdfObject().Get(PdfName.Name); 

       if (t.ToString().Equals("watermark")) 
       { 
         //Not what I want..need to remove the layer 
         layers[i].SetOn(false); 
         //This does not work... 
         //layers.RemoveAt(i); 
        } 
       } 
       pdfDoc.Close(); 

Answer 1

隨着從iText的傢伙，我能夠解決這個問題的幫助。 如果您打算稍後移除水印，則需要將其添加爲「PDF水印註釋」。

要在每個頁面上添加水印：

public void WatermarkPDF(string sourceFile, string destinationPath) 
    { 
     float watermarkTrimmingRectangleWidth = 300; 
     float watermarkTrimmingRectangleHeight = 300; 

     float formWidth = 300; 
     float formHeight = 300; 
     float formXOffset = 0; 
     float formYOffset = 0; 

     float xTranslation = 50; 
     float yTranslation = 25; 

     double rotationInRads = Math.PI/3; 

     PdfFont font = PdfFontFactory.CreateFont(FontConstants.TIMES_ROMAN); 
     float fontSize = 50; 

     PdfDocument pdfDoc = new PdfDocument(new PdfReader(sourceFile), new PdfWriter(destinationPath)); 
     var numberOfPages = pdfDoc.GetNumberOfPages(); 
     PdfPage page = null; 

     for (var i = 1; i <= numberOfPages; i++) 
     { 
      page = pdfDoc.GetPage(i); 
      Rectangle ps = page.GetPageSize(); 

      //Center the annotation 
      float bottomLeftX = ps.GetWidth()/2 - watermarkTrimmingRectangleWidth/2; 
      float bottomLeftY = ps.GetHeight()/2 - watermarkTrimmingRectangleHeight/2; 
      Rectangle watermarkTrimmingRectangle = new Rectangle(bottomLeftX, bottomLeftY, watermarkTrimmingRectangleWidth, watermarkTrimmingRectangleHeight); 

      PdfWatermarkAnnotation watermark = new PdfWatermarkAnnotation(watermarkTrimmingRectangle); 

      //Apply linear algebra rotation math 
      //Create identity matrix 
      AffineTransform transform = new AffineTransform();//No-args constructor creates the identity transform 
      //Apply translation 
      transform.Translate(xTranslation, yTranslation); 
      //Apply rotation 
      transform.Rotate(rotationInRads); 

      PdfFixedPrint fixedPrint = new PdfFixedPrint(); 
      watermark.SetFixedPrint(fixedPrint); 
      //Create appearance 
      Rectangle formRectangle = new Rectangle(formXOffset, formYOffset, formWidth, formHeight); 

      //Observation: font XObject will be resized to fit inside the watermark rectangle 
      PdfFormXObject form = new PdfFormXObject(formRectangle); 
      PdfExtGState gs1 = new PdfExtGState().SetFillOpacity(0.6f); 
      PdfCanvas canvas = new PdfCanvas(form, pdfDoc); 

      float[] transformValues = new float[6]; 
      transform.GetMatrix(transformValues); 
      canvas.SaveState() 
       .BeginText().SetColor(Color.GRAY, true).SetExtGState(gs1) 
       .SetTextMatrix(transformValues[0], transformValues[1], transformValues[2], transformValues[3], transformValues[4], transformValues[5]) 
       .SetFontAndSize(font, fontSize) 
       .ShowText("watermark text") 
       .EndText() 
       .RestoreState(); 

      canvas.Release(); 

      watermark.SetAppearance(PdfName.N, new PdfAnnotationAppearance(form.GetPdfObject())); 
      watermark.SetFlags(PdfAnnotation.PRINT); 

      page.AddAnnotation(watermark); 

     } 
     page?.Flush(); 
     pdfDoc.Close(); 
    } 

去除水印：

public void RemovetWatermarkPDF(string sourceFile, string destinationPath) 
    { 
     PdfDocument pdfDoc = new PdfDocument(new PdfReader(sourceFile), new PdfWriter(destinationPath)); 
     var numberOfPages = pdfDoc.GetNumberOfPages(); 

     for (var i = 1; i <= numberOfPages; i++) 
     { 
      // PdfAnnotation 
      PdfDictionary pageDict = pdfDoc.GetPage(i).GetPdfObject(); 
      PdfArray annots = pageDict.GetAsArray(PdfName.Annots); 
      for (int j = 0; j < annots.Size(); j++) 
      { 
       PdfDictionary annotation = annots.GetAsDictionary(j); 
       if (PdfName.Watermark.Equals(annotation.GetAsName(PdfName.Subtype))) 
       { 
        annotation.Clear(); 
       } 
      } 
     } 
     pdfDoc.Close(); 
    } 

什麼可變長度水印的文字？你將如何動態調整矩形以適應文本？這不是內置到iText的，你需要玩的尺寸如下參數：

float watermarkTrimmingRectangleWidth = 600; 
float watermarkTrimmingRectangleHeight = 600; 
float formWidth = 600; 
float formHeight = 600; 
float formXOffset = -100; 
float fontSize = 30; 

對於我檢查水印文本的長度，我的用例，並基於該調整參數相應例如：

 if (watermarkText.Length <= 14) 
     { 
      watermarkTrimmingRectangleWidth = 200; 
      watermarkTrimmingRectangleHeight = 200; 
      formWidth = 200; 
      formHeight = 200; 
      formXOffset = 0; 
      fontSize = 30; 
     } 
     else if (watermarkText.Length <= 22) 
     { 
      watermarkTrimmingRectangleWidth = 300; 
      watermarkTrimmingRectangleHeight = 300; 
      formWidth = 300; 
      formHeight = 300; 
      formXOffset = 0; 
      fontSize = 30; 
     } 
     else if (...) 
     { 
     ...   
     } 
     . 
     . 
     etc. 
     . 
     . 
     else if (watermarkText.Length <= 62) 
     { 
      watermarkTrimmingRectangleWidth = 600; 
      watermarkTrimmingRectangleHeight = 600; 
      formWidth = 600; 
      formHeight = 600; 
      formXOffset = -100; 
      fontSize = 20; 
     }