Sử dụng iTextSharp để thêm Watermark vào file PDF trong Asp.net

By Unknown - Thursday, September 3, 2015 - No Comments

(How to add Watermark in PDF file using iTextSharp in ASP.NET) – Để bảo vệ bản quyền tác giả đối với các tài liệu khi xuất bản, tác giả thường sử dụng chức năng Watermark. Khi chèn Watermark vào tài liệu, dòng chữ này sẽ hiển thị mờ ở nền mà không ảnh hưởng đến nội dung. Bài viết dưới đây,chúng tôi sẽ giới thiệu với các bạn cách sử dụng thư viện iTextSharp để chèn Watermark vào file PDF. Chương trình sẽ cho phép người sử dụng 1 trong 2 cách đó là sử dụng ký tự (Text) hoặc sử dụng hình ảnh (Image) để chèn Watermark.

Nghe những bài hát đỉnh nhất về Thấy cô giáo - Nghe trên Youtube

- B1: Tạo Project trong Microsoft Visual Studio 2010

- B2: Download thư viện iTextSharp tại đây

- B3: References itextsharp.dll trong thư mục vừa giải nén vào Project.

- B4: Mở file Default.aspx dưới dạng HTML và nhập mã HTML
C#

<%@ Page Title="Add Watermark to PDF Using iTextSharp in ASP.NET" Language="C#" MasterPageFile="~/Site.master" AutoEventWireup="true" CodeBehind="Default.aspx.cs" Inherits="AddWatermarkToPDFUsingiTextSharp._Default" %>

<asp:Content ID="BodyContent" runat="server" ContentPlaceHolderID="MainContent">

<tr>

<td>

<asp:label id="lblHeader" runat="server" Text="Add Watermark to PDF Using iTextSharp in ASP.NET"></asp:label>

</div>

<tr>

<asp:Label ID="plWatermarkText" runat="server" Text="WatermarkText"></asp:Label>

</td>

<td>

<asp:TextBox ID="txtWatermarkText" CssClass="form-control" Width="280px" runat="server"></asp:TextBox>

<asp:RequiredFieldValidator ID="valWatermarkText" CssClass="NormalRed" ValidationGroup="Text" runat="server" ErrorMessage="Enter Watermark Text" ControlToValidate="txtWatermarkText"></asp:RequiredFieldValidator>

</td>

</tr>

</table>

</div>

<asp:LinkButton id="cmdInsert" runat="server" CssClass="btn btn-small" ValidationGroup="Text" OnClick="cmdInsert_Click" Causesvalidation="true">

</asp:LinkButton>

<asp:LinkButton id="cmdInsertImage" runat="server" CssClass="btn btn-small" OnClick="cmdInsertImage_Click" Causesvalidation="true">

</asp:LinkButton>

</div>

</td>

</tr>

</table>

</asp:Content>

VB.NET Code

<%@ Page Title="Add Watermark to PDF Using iTextSharp in ASP.NET" Language="vb" MasterPageFile="~/Site.Master" AutoEventWireup="false" CodeBehind="Default.aspx.vb" Inherits="AddWatermarkToPDFUsingiTextSharp._Default" %>

<asp:Content ID="BodyContent" runat="server" ContentPlaceHolderID="MainContent">

<tr>

<td>

<asp:label id="lblHeader" runat="server" Text="Add Watermark to PDF Using iTextSharp in ASP.NET"></asp:label>

</div>

<tr>

<asp:Label ID="plWatermarkText" runat="server" Text="WatermarkText"></asp:Label>

</td>

<td>

<asp:TextBox ID="txtWatermarkText" CssClass="form-control" Width="280px" runat="server"></asp:TextBox>

</td>

</tr>

</table>

</div>

<asp:LinkButton id="cmdInsertText" runat="server" CssClass="btn btn-small" ValidationGroup="Text" Causesvalidation="true">

</asp:LinkButton>

<asp:LinkButton id="cmdInsertImage" runat="server" CssClass="btn btn-small" Causesvalidation="true">

</asp:LinkButton>

</div>

</td>

</tr>

</table>

</asp:Content>

- B5: Viết Code cho file Default.aspx

C# Code

//Visit http://www.laptrinhdotnet.com for more ASP.NET Tutorials

using Microsoft.VisualBasic;

using System;

using System.Collections;

using System.Collections.Generic;

using System.Data;

using System.IO;

using System.Text;

using System.Web.UI;

using System.Web;

using iTextSharp.text.html;

using iTextSharp.text;

using iTextSharp.text.html.simpleparser;

using iTextSharp.text.pdf;

namespace AddWatermarkToPDFUsingiTextSharp

{

public partial class _Default : System.Web.UI.Page

{

#region "Add Watermark"

private void AddWatermarkToPDFUsingiTextSharp(string FileName, bool IsText)

{

Document oDoc = new Document(PageSize.A4, 20f, 20f, 30f, 20f);

oDoc.SetPageSize(iTextSharp.text.PageSize.A4.Rotate());

System.IO.MemoryStream msReport = new System.IO.MemoryStream();

string WatermarkText = "www.laptrinhdotnet.com";

string ImagePath = Server.MapPath("Images\\dotnet.jpg");

float fontSize = 45;

float xPosition = (iTextSharp.text.PageSize.A4.Width + 320f) / 2;

float yPosition = (iTextSharp.text.PageSize.A4.Height - 220f) / 2;

float angle = 45;

BaseFont baseFont = BaseFont.CreateFont(BaseFont.HELVETICA, BaseFont.WINANSI, BaseFont.EMBEDDED);

try

{

PdfWriter writer = PdfWriter.GetInstance(oDoc, msReport);

oDoc.AddAuthor("laptrinhdotnet.com");

oDoc.AddSubject("Add Watermark To PDF");

oDoc.Open();

PdfContentByte ContentUnder = writer.DirectContentUnder;

if (IsText)

{

if (!string.IsNullOrEmpty(txtWatermarkText.Text))

{

WatermarkText = txtWatermarkText.Text.Trim();

}

xPosition = (iTextSharp.text.PageSize.A4.Width + 320f) / 2;

yPosition = (iTextSharp.text.PageSize.A4.Height - 220f) / 2;

ContentUnder.BeginText();

ContentUnder.SetColorFill(iTextSharp.text.pdf.CMYKColor.LIGHT_GRAY);

ContentUnder.SetFontAndSize(baseFont, fontSize);

ContentUnder.ShowTextAligned(PdfContentByte.ALIGN_CENTER, WatermarkText, xPosition, yPosition, angle);

ContentUnder.EndText();

}

else

{

if (File.Exists(ImagePath))

{

xPosition = (iTextSharp.text.PageSize.A4.Width) / 2;

yPosition = (iTextSharp.text.PageSize.A4.Height - 220f) / 2;

Image pdfImage = Image.GetInstance(ImagePath);

pdfImage.SetAbsolutePosition(xPosition, yPosition);

ContentUnder.AddImage(pdfImage);

}

catch

{

}

oDoc.Close();

Response.Clear();

Response.AddHeader("content-disposition", "attachment;filename=" + FileName + ".pdf");

Response.ContentType = "application/pdf";

Response.BinaryWrite(msReport.ToArray());

Response.End();

}

#endregion

#region "Event Handles"

protected void cmdInsert_Click(object sender, System.EventArgs e)

{

AddWatermarkToPDFUsingiTextSharp("AddWatermark",true);

}

protected void cmdInsertImage_Click(object sender, System.EventArgs e)

{

AddWatermarkToPDFUsingiTextSharp("AddWatermark", false);

}

#endregion

}

VB.NET Code

'Visit http://www.laptrinhdotnet.com for more ASP.NET Tutorials

Imports iTextSharp.text.html

Imports iTextSharp.text

Imports iTextSharp.text.html.simpleparser

Imports iTextSharp.text.pdf

Imports System.IO

Namespace AddWatermarkToPDFUsingiTextSharp

Public Class _Default

Inherits System.Web.UI.Page

#Region "Add Watermark"

Private Sub AddWatermarkToPDFUsingiTextSharp(ByVal FileName As String, ByVal IsText As Boolean)

Dim oDoc As New Document(PageSize.A4.Rotate, 20, 20, 30, 20)

oDoc.SetPageSize(iTextSharp.text.PageSize.A4.Rotate())

Dim msReport As New System.IO.MemoryStream()

Dim WatermarkText As String = "www.laptrinhdotnet.com"

Dim fontSize As Single = 45

Dim xPosition As Single = 0

Dim yPosition As Single = 0

Dim angle As Single = 45

Dim ImagePath As String = Server.MapPath("Images\dotnet.jpg")

Dim baseFont As BaseFont = baseFont.CreateFont(baseFont.HELVETICA, baseFont.WINANSI, baseFont.EMBEDDED)

Try

Dim writer As PdfWriter = PdfWriter.GetInstance(oDoc, msReport)

oDoc.AddAuthor("laptrinhdotnet.com")

oDoc.AddSubject("Add Watermark To PDF")

oDoc.Open()

Dim ContentUnder As PdfContentByte = writer.DirectContentUnder

If IsText Then

xPosition = (iTextSharp.text.PageSize.A4.Width + 320.0F) / 2

yPosition = (iTextSharp.text.PageSize.A4.Height - 220.0F) / 2

If txtWatermarkText.Text <> "" Then

WatermarkText = txtWatermarkText.Text.Trim

End If

With ContentUnder

.BeginText()

.SetColorFill(iTextSharp.text.pdf.CMYKColor.LIGHT_GRAY)

.SetFontAndSize(baseFont, fontSize)

.ShowTextAligned(PdfContentByte.ALIGN_CENTER, WatermarkText, xPosition, yPosition, angle)

.EndText()

End With

Else

If File.Exists(ImagePath) Then

xPosition = (iTextSharp.text.PageSize.A4.Width) / 2

yPosition = (iTextSharp.text.PageSize.A4.Height - 220.0F) / 2

Dim pdfImage As Image = Image.GetInstance(ImagePath)

pdfImage.SetAbsolutePosition(xPosition, yPosition)

ContentUnder.AddImage(pdfImage)

End If

Catch e As Exception

Console.Error.WriteLine(e.Message)

End Try

oDoc.Close()

Response.Clear()

Response.AddHeader("content-disposition", "attachment;filename=" & FileName & ".pdf")

Response.ContentType = "application/pdf"

Response.BinaryWrite(msReport.ToArray())

Response.End()

End Sub

#End Region

#Region "Event Handles"

Private Sub cmdInsertText_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles cmdInsertText.Click

AddWatermarkToPDFUsingiTextSharp("AddWatermark", True)

End Sub

Private Sub cmdInsertImage_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles cmdInsertImage.Click

AddWatermarkToPDFUsingiTextSharp("AddWatermark", False)

End Sub

#End Region

End Class

End Namespace

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