(How to add Watermark Text to an image dynamically while uploading in ASP.NET) – Trong bài viết trước chúng tôi đã giới thiệu cách thêm Watermark vào ảnh bằng một hình ảnh được thiết lập mặc định. Với cách này, Watermark sẽ đẹp hơn do được sử dụng bằng hình ảnh tuy nhiên nó lại không chủ động cho người sử dụng trong việc thay đổi thông tin. Bài viết dưới đây sẽ hướng dẫn cho các bạn thêm một cách để add Watermark vào hình ảnh bằng Text. Với cách này người dùng hoàn toàn có thể chủ động hoàn toàn trong việc đưa thông tin Watermark vào ảnh.

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

- B1: Tạo Project trong Microsoft Visual Studio 2010

- B2: Mở file Default.aspx dưới dạng HTML và nhập mã HTML

C# Code

<%@ PageTitle="Add Watermark Text on Uploaded Image in Asp.Net" Language="C#"MasterPageFile="~/Site.master"AutoEventWireup="true"CodeBehind="Default.aspx.cs"Inherits="AddWatermarkTextOnUploaded._Default"%>

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

<tr>

<td>

<divclass="panel panel-default">

<divclass="panel-heading">

<asp:label id="lblHeader" runat="server" Text="Add Watermark Text on Uploaded Image in Asp.Net"></asp:label>

</div>

<divclass="panel-body">

<tr>

<asp:label id="plWatermarkText"runat="server"Text="WatermarkText (*)"></asp:label>

</td>

<td>

<asp:TextBox ID="txtWatermarkText"CssClass="form-control"runat="server"Width="250px"></asp:TextBox>

<asp:RequiredFieldValidatorID="valWatermarkText"ValidationGroup="validate"runat="server"ControlToValidate="txtWatermarkText"Display="dynamic" ErrorMessage="Enter Watermark Text"></asp:RequiredFieldValidator>

</td>

</tr>

<tr>

<td>

<asp:label id="plImageName"runat="server"Text="Image Name (*)"></asp:label>

</td>

<td>

<asp:FileUpload ID="FileUpload"runat="server"Width="150px"/><br />

<asp:CustomValidator id="valFile"runat="server"CssClass="NormalRed"ValidationGroup="validate"ErrorMessage="You Must Upload A File" Display="Dynamic"></asp:CustomValidator>

<asp:CustomValidator id="valType"runat="server"CssClass="NormalRed"ValidationGroup="validate"Display="Dynamic"></asp:CustomValidator>

</td>

</tr>

<tr>

<asp:Image ID="imgPreview"Visible="false"runat="server"/>

</td>

</tr>

<tr>

<asp:label id="lblMessage"runat="server"Visible="false"></asp:label>

</td>

</tr>

</table>

</div>

<divclass="modal-footer">

<asp:LinkButton id="cmdUpload"runat="server"CssClass="btn btn-small" OnClick="cmdUpload_Click" ValidationGroup="validate" Causesvalidation="true">

</asp:LinkButton>

</div>

</td>

</tr>

</table>

</asp:Content>

VB.NET Code

<%@ PageTitle="Add Watermark Text on Uploaded Image in Asp.Net" Language="vb"MasterPageFile="~/Site.Master"AutoEventWireup="false"CodeBehind="Default.aspx.vb"Inherits="AddWatermarkTextOnUploaded._Default"%>

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

<tr>

<td>

<divclass="panel panel-default">

<divclass="panel-heading">

<asp:label id="lblHeader" runat="server" Text="Add Watermark Text on Uploaded Image in Asp.Net"></asp:label>

</div>

<divclass="panel-body">

<tr>

<asp:label id="plWatermarkText"runat="server"Text="WatermarkText (*)"></asp:label>

</td>

<td>

<asp:TextBox ID="txtWatermarkText"CssClass="form-control"runat="server"Width="250px"></asp:TextBox>

<asp:RequiredFieldValidatorID="valWatermarkText"runat="server"ValidationGroup="validate"ControlToValidate="txtWatermarkText"Display="dynamic" ErrorMessage="Enter Watermark Text"></asp:RequiredFieldValidator>

</td>

</tr>

<tr>

<td>

<asp:label id="plImageName"runat="server"Text="Image Name (*)"></asp:label>

</td>

<td>

<asp:FileUpload ID="FileUpload"runat="server"Width="150px"/><br />

<asp:CustomValidator id="valFile"runat="server"CssClass="NormalRed"ValidationGroup="validate"ErrorMessage="You Must Upload A File" Display="Dynamic"></asp:CustomValidator>

<asp:CustomValidator id="valType"runat="server"CssClass="NormalRed"ValidationGroup="validate"Display="Dynamic"></asp:CustomValidator>

</td>

</tr>

<tr>

<asp:Image ID="imgPreview"Visible="false"runat="server"/>

</td>

</tr>

<tr>

<asp:label id="lblMessage"runat="server"Visible="false"></asp:label>

</td>

</tr>

</table>

</div>

<divclass="modal-footer">

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

</asp:LinkButton>

</div>

</td>

</tr>

</table>

</asp:Content>

- B3: 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.Diagnostics;

using System.Web.UI;

using System.Web;

using System.Drawing;

using System.Web.UI.WebControls;

namespace AddWatermarkTextOnUploaded

{

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

{

#region"Private Members"

private stringFilePath;

private stringFileFilter = "gif,jpg,jpeg,png";

#endregion

#region"Private Methods"

protected stringUploadFile(FileUpload Upload)

{

string fileName = "";

string fileExtension = "";

SetFilePath();

System.Drawing.Image bmpUpload = System.Drawing.Image.FromStream(Upload.PostedFile.InputStream);

fileExtension = Path.GetExtension(Upload.FileName).Replace(".", "");

fileName = Upload.FileName.Substring(Upload.FileName.LastIndexOf("\\\\") + 1);

fileName = fileName.Substring(0, fileName.LastIndexOf(fileExtension)) + fileExtension;

FilePath = FilePath + fileName;

using (Graphics g = Graphics.FromImage(bmpUpload))

{

int opacity = 128;

SolidBrushbrush = new SolidBrush(Color.FromArgb(opacity, Color.White));

Font font = newFont("Arial", 16, FontStyle.Bold);

g.DrawString(txtWatermarkText.Text.Trim(), font, brush, new PointF(bmpUpload.Width / 15, bmpUpload.Height / 15));

bmpUpload.Save(Path.Combine(FilePath));

imgPreview.ImageUrl = ResolveUrl("~/Upload/") + fileName;

imgPreview.Visible = true;

}

return fileName;

}

private voidSetFilePath()

{

FilePath = MapPath("~/Upload/");

//Create Folder

if (!Directory.Exists(FilePath))

{

Directory.CreateDirectory(FilePath);

}

#endregion

#region"Event Handles"

protected voidcmdUpload_Click(object sender, System.EventArgs e)

{

if (Page.IsValid)

{

try

{

stringfileName = "";

if (!string.IsNullOrEmpty(FileUpload.PostedFile.FileName))

{

fileName = UploadFile(FileUpload);

if (!string.IsNullOrEmpty(fileName))

{

lblMessage.Text = "Upload file Sucessfully";

lblMessage.ForeColor = System.Drawing.Color.Green;

lblMessage.Visible = true;

}

catch (Exceptionex)

{

lblMessage.Text = ex.Message;

lblMessage.ForeColor = System.Drawing.Color.Red;

lblMessage.Visible = true;

return;

}

protected voidvalFile_ServerValidate(object source, ServerValidateEventArgs args)

{

if (FileUpload.PostedFile != null)

{

if (FileUpload.PostedFile.ContentLength > 0)

{

args.IsValid = true;

}

else

{

args.IsValid = false;

}

protected voidvalType_ServerValidate(object source, ServerValidateEventArgs args)

{

if (FileUpload.PostedFile != null)

{

lblMessage.Visible = false;

if (FileUpload.PostedFile.ContentLength > 0)

{

string[] arr = FileUpload.PostedFile.FileName.Split(Convert.ToChar('.'));

string FileType = arr[arr.Length - 1].ToLower();

valType.ErrorMessage = "You must upload a file that is either a gif, jpg, jpeg, png";

if (FileFilter.IndexOf(FileType) > -1)

{

args.IsValid = true;

}

else

{

args.IsValid = false;

}

else

{

args.IsValid = false;

}

#endregion

}

VB.NET Code

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

Imports System.IO

Imports System.Drawing

Namespace AddWatermarkTextOnUploaded

Public Class _Default

Inherits System.Web.UI.Page

#Region "Private Members"

Private FilePath As String = ""

Private FileFilter AsString = "gif,jpg,jpeg,png"

#End Region

#Region "Private Methods"

Protected FunctionUploadFile(ByVal Upload As FileUpload) As String

Dim fileName As String = ""

Dim fileExtension As String = ""

SetFilePath()

Dim bmpUpload As Image = Image.FromStream(Upload.PostedFile.InputStream)

fileExtension = Replace(Path.GetExtension(Upload.FileName), ".", "")

fileName = Upload.FileName.Substring(Upload.FileName.LastIndexOf("\\") + 1)

fileName = fileName.Substring(0, fileName.LastIndexOf(fileExtension)) & fileExtension

FilePath = FilePath + fileName

Using g As Graphics = Graphics.FromImage(bmpUpload)

Dim opacity AsInteger = 128

Dim brush AsNew SolidBrush(Color.FromArgb(opacity, Color.White))

Dim font AsNew Font("Arial", 16, FontStyle.Bold)

g.DrawString(txtWatermarkText.Text.Trim, font, brush, New PointF(bmpUpload.Width / 15, bmpUpload.Height / 15))

bmpUpload.Save(Path.Combine(FilePath))

imgPreview.ImageUrl = ResolveUrl("~/Upload/") & fileName

imgPreview.Visible = True

End Using

Return fileName

End Function

Private SubSetFilePath()

FilePath = MapPath("~/Upload/")

'Create Folder

If Not Directory.Exists(FilePath) Then

Directory.CreateDirectory(FilePath)

End If

End Sub

#End Region

#Region "Event Handles"

Private SubcmdUpload_Click(ByVal sender As Object, ByVal e As System.EventArgs) HandlescmdUpload.Click

If Page.IsValid Then

Try

Dim fileName AsString = ""

If FileUpload.PostedFile.FileName <> "" Then

fileName = UploadFile(FileUpload)

If fileName <> ""Then

lblMessage.Text = "Upload file Sucessfully"

lblMessage.ForeColor = System.Drawing.Color.Green

lblMessage.Visible = True

End If

Catch ex AsException

lblMessage.Text = ex.Message

lblMessage.ForeColor = System.Drawing.Color.Red

lblMessage.Visible = True

Exit Sub

End Try

End If

End Sub

Private SubvalFile_ServerValidate(ByVal source As System.Object, ByVal args AsSystem.Web.UI.WebControls.ServerValidateEventArgs) Handles valFile.ServerValidate

Try

If NotFileUpload.PostedFile Is Nothing Then

If FileUpload.PostedFile.ContentLength > 0 Then

args.IsValid = True

Return

End If

args.IsValid = False

Catch exc As Exception

End Try

End Sub

Private SubvalType_ServerValidate(ByVal source As System.Object, ByVal args AsSystem.Web.UI.WebControls.ServerValidateEventArgs) Handles valType.ServerValidate

Try

If Not(FileUpload.PostedFile Is Nothing) Then

lblMessage.Visible = False

If (FileUpload.PostedFile.ContentLength > 0) Then

Dim arr As String() = FileUpload.PostedFile.FileName.Split(Convert.ToChar("."))

Dim fileType As String = arr(arr.Length - 1).ToLower()

valType.ErrorMessage = "You must upload a file that is either a gif, jpg, jpeg, png"

If FileFilter <> ""And Not InStr("," & FileFilter.ToLower, "," & fileType.ToLower) = 0 Then

args.IsValid = True

Return

Else

args.IsValid = False

End If

args.IsValid = False

End If

Catch exc As Exception

End Try

End Sub

#End Region

End Class

End Namespace

Chúc các bạn thành công!

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Add Watermark Text on Uploaded Image in Asp.Net

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