iText 7-在PDF上添加和删除水印 [英] iText 7 - Add and Remove Watermark on a PDF

问题描述

我想使用iText 7向PDF添加和删除水印.我能够添加水印，但无法再次将其删除.我只能找到与iText 5相关的相关代码/示例.感谢任何指针，谢谢.

I would like to add and remove a watermark to a PDF using iText 7. I was able to add the watermark, but unable to remove it again. I could only find relevant code/examples related to iText 5. Any pointers appreciated, thanks.

这是我添加水印(使用图层)的方式:

This is how I added the Watermark (using Layers):

            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();

这是我尝试删除的水印.我想将其完全删除，而不仅仅是将图层设置为不显示.(赞赏任何示例代码):

This is what I have tried to remove the watermark. I want to remove it completely, not just set the layer to not display.(any sample code appreciated):

            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();

推荐答案

在iText的帮助下，我得以解决此问题. 如果您打算以后删除水印，则需要将其添加为"PDF水印注释".

With help from the guys at iText I was able to solve this. If you intend to remove the watermark later, you will need to add it as a 'PDF watermark annotation'.

要在每个页面上添加水印:

To add a watermark on every page:

    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();
    } 

要删除水印:

    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();
    }

可变长度水印文本怎么办?您将如何动态调整矩形的大小以适合文本?这不是iText内置的，您需要使用以下尺寸参数:

What about variable length watermark text? How would you dynamically resize the rectangle to fit the text? This is not inbuilt into iText, you would need to play around with the following dimension parameters:

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

在我的用例中，我检查了水印文本的长度，并据此调整了参数，例如:

For my use-case I checked the length of the watermark text and based on that adjusted the parameters accordingly eg:

        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;
        }

这篇关于iText 7-在PDF上添加和删除水印的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！