Hello. I am new to ASP.NET. I am displaying an image in a web page, and I would like to add a watermark to it. I am retrieving the image from a database and displaying it directly without writing to a file. I found some sample code and modified it to work
as I wanted it to, except now I need to add the watermark. I am not sure how to go about doing that, and I am hoping someone can take the code below and show me how to modify it to add a watermark. The watermark can be another image or text.
Protected Sub getPicture(ByRef aID As String, ByRef imageControl As System.Web.UI.WebControls.Image)
Dim ConnString As String = ConfigurationManager.ConnectionStrings("DBConnString").ConnectionString
Dim dr As SqlDataReader = Nothing
Using con As New SqlConnection(ConnString)
Using cmd As New SqlCommand("SELECT * FROM aDB WHERE ID=" & aID, con)
cmd.CommandType = CommandType.Text
con.Open()
dr = cmd.ExecuteReader()
If dr.HasRows Then
dr.Read()
If Not IsDBNull(dr.GetValue(dr.GetOrdinal("IMAGE"))) Then
Dim aPicture() As Byte = dr.GetProviderSpecificValue(dr.GetOrdinal("IMAGE")).Value
Dim base64String As String = Convert.ToBase64String(aPicture, 0, aPicture.Length)
imageControl.ImageUrl = Convert.ToString("data:image/png;base64,") & base64String
End If
End If
dr.Close()
con.Close()
End Using
End Using
End Sub
how to modify it to add a watermark. The watermark can be another image or text.
There are lot of commercial products to add high-quality watermark and copyright text for images. But, you can use System.Drawing to create watermark or additional text. But, you would have to convert the blob data or the value you are getting from database
to stream. Then, check the below link for sample code.
You would have to use Drawing.Image.FromStream() instead of Drawing.Image.FromFile() as you are not saving the image data to a file. I would recommend creating a helper class with a method to create watermark and calling that method from your page. You
can also add watermark at runtime which updates images through HttpHandlers
The WebImage class is in System.Web.Helpers which is part of the ASP.NET Web Pages framework. If you are using Web Forms or MVC, you will need to add a reference to the assembly (System.Web.Helpers.dll). It can usually be found in C:\Program Files (x86)\Microsoft
ASP.NET\ASP.NET Web Pages\v2.0\Assemblies
You code will look something like this (not tested)
Protected Sub getPicture(ByRef aID As String, ByRef imageControl As System.Web.UI.WebControls.Image)
Dim ConnString As String = ConfigurationManager.ConnectionStrings("DBConnString").ConnectionString
Dim dr As SqlDataReader = Nothing
Using con As New SqlConnection(ConnString)
Using cmd As New SqlCommand("SELECT * FROM aDB WHERE ID=" & aID, con)
cmd.CommandType = CommandType.Text
con.Open()
dr = cmd.ExecuteReader()
If dr.HasRows Then
dr.Read()
If Not IsDBNull(dr.GetValue(dr.GetOrdinal("IMAGE"))) Then
Dim image As New WebImage(dr.GetProviderSpecificValue(dr.GetOrdinal("IMAGE")).Value)
image.AddTextWaterMark("Some Text")
Dim aPicture() as Byte() = image.GetBytes()
Dim base64String As String = Convert.ToBase64String(aPicture, 0, aPicture.Length)
imageControl.ImageUrl = Convert.ToString("data:image/png;base64,") & base64String
End If
End If
dr.Close()
con.Close()
End Using
End Using
End Sub
Thank you! That appears to work fine. I had to install MVC 3 (http://www.asp.net/mvc/mvc3), but once I did that then I was able to add the reference. Just for anyone else's information that may need this, I had to
change the code you provided slightly. Just wanted to respond back so it would be here for others:
Protected Sub getPicture(ByRef aID As String, ByRef imageControl As System.Web.UI.WebControls.Image)
Dim ConnString As String = ConfigurationManager.ConnectionStrings("DBConnString").ConnectionString
Dim dr As SqlDataReader = Nothing
Using con As New SqlConnection(ConnString)
Using cmd As New SqlCommand("SELECT * FROM aDB WHERE ID=" & aID, con)
cmd.CommandType = CommandType.Text
con.Open()
dr = cmd.ExecuteReader()
If dr.HasRows Then
dr.Read()
If Not IsDBNull(dr.GetValue(dr.GetOrdinal("IMAGE"))) Then
Dim aPicture() As Byte = dr.GetProviderSpecificValue(dr.GetOrdinal("IMAGE")).Value
Dim image As New WebImage(aPicture)
image.AddTextWaterMark("Some Text")
Dim base64String As String = Convert.ToBase64String(image.GetBytes, 0, image.GetBytes.Length)
imageControl.ImageUrl = Convert.ToString("data:image/png;base64,") & base64String
End If
End If
dr.Close()
con.Close()
End Using
End Using
End Sub
M-Clark
Member
4 Points
66 Posts
Question regarding images and adding watermark.
Mar 14, 2014 12:31 PM|M-Clark|LINK
Hello. I am new to ASP.NET. I am displaying an image in a web page, and I would like to add a watermark to it. I am retrieving the image from a database and displaying it directly without writing to a file. I found some sample code and modified it to work as I wanted it to, except now I need to add the watermark. I am not sure how to go about doing that, and I am hoping someone can take the code below and show me how to modify it to add a watermark. The watermark can be another image or text.
Protected Sub getPicture(ByRef aID As String, ByRef imageControl As System.Web.UI.WebControls.Image) Dim ConnString As String = ConfigurationManager.ConnectionStrings("DBConnString").ConnectionString Dim dr As SqlDataReader = Nothing Using con As New SqlConnection(ConnString) Using cmd As New SqlCommand("SELECT * FROM aDB WHERE ID=" & aID, con) cmd.CommandType = CommandType.Text con.Open() dr = cmd.ExecuteReader() If dr.HasRows Then dr.Read() If Not IsDBNull(dr.GetValue(dr.GetOrdinal("IMAGE"))) Then Dim aPicture() As Byte = dr.GetProviderSpecificValue(dr.GetOrdinal("IMAGE")).Value Dim base64String As String = Convert.ToBase64String(aPicture, 0, aPicture.Length) imageControl.ImageUrl = Convert.ToString("data:image/png;base64,") & base64String End If End If dr.Close() con.Close() End Using End Using End Subdotnetzoom
Contributor
5590 Points
1297 Posts
Re: Question regarding images and adding watermark.
Mar 16, 2014 05:06 AM|dotnetzoom|LINK
M-Clark
There are lot of commercial products to add high-quality watermark and copyright text for images. But, you can use System.Drawing to create watermark or additional text. But, you would have to convert the blob data or the value you are getting from database to stream. Then, check the below link for sample code.
You would have to use Drawing.Image.FromStream() instead of Drawing.Image.FromFile() as you are not saving the image data to a file. I would recommend creating a helper class with a method to create watermark and calling that method from your page. You can also add watermark at runtime which updates images through HttpHandlers
Try the first approach and see if it works.
Mikesdotnett...
All-Star
184243 Points
26625 Posts
Moderator
MVP
Re: Question regarding images and adding watermark.
Mar 16, 2014 05:20 AM|Mikesdotnetting|LINK
You can use the WebImage class to do this. It has an AddTextWaterMark method: http://msdn.microsoft.com/en-us/library/system.web.helpers.webimage_methods(v=vs.111).aspx
The WebImage class is in System.Web.Helpers which is part of the ASP.NET Web Pages framework. If you are using Web Forms or MVC, you will need to add a reference to the assembly (System.Web.Helpers.dll). It can usually be found in C:\Program Files (x86)\Microsoft ASP.NET\ASP.NET Web Pages\v2.0\Assemblies
You code will look something like this (not tested)
Protected Sub getPicture(ByRef aID As String, ByRef imageControl As System.Web.UI.WebControls.Image) Dim ConnString As String = ConfigurationManager.ConnectionStrings("DBConnString").ConnectionString Dim dr As SqlDataReader = Nothing Using con As New SqlConnection(ConnString) Using cmd As New SqlCommand("SELECT * FROM aDB WHERE ID=" & aID, con) cmd.CommandType = CommandType.Text con.Open() dr = cmd.ExecuteReader() If dr.HasRows Then dr.Read() If Not IsDBNull(dr.GetValue(dr.GetOrdinal("IMAGE"))) Then Dim image As New WebImage(dr.GetProviderSpecificValue(dr.GetOrdinal("IMAGE")).Value) image.AddTextWaterMark("Some Text") Dim aPicture() as Byte() = image.GetBytes() Dim base64String As String = Convert.ToBase64String(aPicture, 0, aPicture.Length) imageControl.ImageUrl = Convert.ToString("data:image/png;base64,") & base64String End If End If dr.Close() con.Close() End Using End Using End SubASP.NET Tutorials | Learn Entity Framework Core
M-Clark
Member
4 Points
66 Posts
Re: Question regarding images and adding watermark.
Mar 17, 2014 04:11 PM|M-Clark|LINK
Thank you! That appears to work fine. I had to install MVC 3 (http://www.asp.net/mvc/mvc3), but once I did that then I was able to add the reference. Just for anyone else's information that may need this, I had to change the code you provided slightly. Just wanted to respond back so it would be here for others:
Protected Sub getPicture(ByRef aID As String, ByRef imageControl As System.Web.UI.WebControls.Image) Dim ConnString As String = ConfigurationManager.ConnectionStrings("DBConnString").ConnectionString Dim dr As SqlDataReader = Nothing Using con As New SqlConnection(ConnString) Using cmd As New SqlCommand("SELECT * FROM aDB WHERE ID=" & aID, con) cmd.CommandType = CommandType.Text con.Open() dr = cmd.ExecuteReader() If dr.HasRows Then dr.Read() If Not IsDBNull(dr.GetValue(dr.GetOrdinal("IMAGE"))) Then Dim aPicture() As Byte = dr.GetProviderSpecificValue(dr.GetOrdinal("IMAGE")).Value Dim image As New WebImage(aPicture) image.AddTextWaterMark("Some Text") Dim base64String As String = Convert.ToBase64String(image.GetBytes, 0, image.GetBytes.Length) imageControl.ImageUrl = Convert.ToString("data:image/png;base64,") & base64String End If End If dr.Close() con.Close() End Using End Using End SubThanks again!
Mikesdotnett...
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Moderator
MVP
Re: Question regarding images and adding watermark.
Mar 17, 2014 04:18 PM|Mikesdotnetting|LINK
Alternatively, you could have installed ASP.NET Web Pages: http://www.asp.net/web-pages but you would have ended up with WebMatrix too.
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