Build a simple Watermarking utility in VB.NET

Introduction

This article shall describe an approach to building a simple watermarking utility that may be used to add watermarks to any supported image file format. The resulting application shall permit the user to open any supported image file format into a scrollable picture box, to define the text to be applied as a watermark (with a default version supplied), to set the font and color of the watermark, to define the opacity of the watermark, to determine whether or not the watermark appears at the top or bottom of the image, and to preview the watermark prior to saving it to the image.

Figure 1: the Utility Application showing a Watermarked Image

If you are at all curious about the image, it is of an American Goldfinch, this time of year, I have a about 50 or so such birds hanging around my bird feeders.I tookthe picture with myFuji S700 digital camera through the kitchen window.

Getting Started

The solution contains a single Windows Forms project called â€œWatermarkingVBâ€ written in Visual Basic 2005; the application contains only a single form (frmWatermark.vb) and all of the code necessary to drive the application is contained in that single form class.

Figure 2: Solution Explorer with the Project Visible

Code: Watermarking Main Form (frmWatermark.vb)

All of the code necessary for this project is contained in this single form; that form shall be described entirely in this section.

The code for this form class begins with the following:

Imports System.Drawing

Imports System.Drawing.Drawing2D

Imports System.Drawing.Imaging

Imports System.Text

''' <summary>

''' An Image Watermarking Utility

''' </summary>

''' <remarks></remarks>

Public Class frmWatermark

Following the declaration of the form class, the next order of business in the application is to declare a collection of member variables requiring form wide scope; these variables are contained in a defined region entitled, â€œMember Variablesâ€. The declaration of the variables follows; as can been determined, the variables are used to keep track of the current file location and image, codec and encoder information used to translate the image from one format to another, and the color and font used to display the image watermark.

#Region "Member Variables"

Private CurrentFile As String

Private img As Image

Private myImageCodecInfo As ImageCodecInfo

Private myEncoder As System.Drawing.Imaging.Encoder

Private myEncoderParameter As EncoderParameter

Private myEncoderParameters As EncoderParameters

Private myWatermarkColor As System.Drawing.Color

Private myFont As System.Drawing.Font

#End Region

The next block of code in the form class is the constructor; in this instance, the constructor is used to establish a default configuration including the definition of the watermark color, the opacity level of the watermark, the positioning option (top or bottom), the text contained in the watermark, and the font used to display the watermark.

#Region "Constructor"

''' <summary>

''' Constructor with default settings

''' </summary>

''' <remarks></remarks>

Public Sub New()

InitializeComponent()

' setup default settings

myWatermarkColor = Color.SteelBlue

cboOpacity.SelectedIndex = 2

optTop.Checked = True

txtWaterMark.Text = "Your Name " & _Char.ConvertFromUtf32(169).ToString() & " " & _

myFont = txtWaterMark.Font

End Sub

#End Region

Following the constructor, there is a region defined to handle file input/output operations. This region contains two event handlers, one for the selection of the Open File menu strip option, and one for the save buttonsâ€™s click event. The open file menu option is used to allow the user to navigate to and select an image file for load; the selected image file is placed into a scrollable picturebox.

The save button click event handler is used to save the image file with the watermark; the original file may be renamed or overwritten.

#Region "File IO"

Private Sub openToolStripMenuItem_Click(ByVal sender As System.Object, _ByVal e As System.EventArgs) Handles openToolStripMenuItem.Click

' configure the open file dialog to point to some

' common (usable) image file formats

openFileDialog1.Title = "Open Image File"

& _"|Gif Files|*.gif|JPEG Files|*.jpg" & _"|PNG Files|*.png|TIFF Files|*.tif|Windows MetaFile|*.wmf"

openFileDialog1.DefaultExt = "bmp"

openFileDialog1.FilterIndex = 1

openFileDialog1.FileName = ""

openFileDialog1.ShowDialog()

' if the user did not select a file, return

If (openFileDialog1.FileName = "") Then Return

' update the current file and form caption text

CurrentFile = openFileDialog1.FileName.ToString()

Me.Text = "Watermark Utility: " & CurrentFile.ToString()

Try

' open the image into the picture box

img = Image.FromFile(openFileDialog1.FileName, True)

picContainer.Image = img

' resize the picture box to support scrolling

' large images

picContainer.Size = img.Size

Catch ex As Exception

MessageBox.Show(ex.Message, "File Open Error")

End Try

End Sub

Private Sub btnSave_Click(ByVal sender As System.Object, _ByVal e As System.EventArgs) Handles btnSave.Click

Try

' get the extension to figure out how to limit the save

' option to the current image file type

Dim strExt As String

strExt = System.IO.Path.GetExtension(CurrentFile)

strExt = strExt.ToUpper()

strExt = strExt.Remove(0, 1)

' if the current image is, for example, a gif, only

' allow the user to save the file with the watermark

' as a gif

SaveFileDialog1.Title = "Save File"

SaveFileDialog1.DefaultExt = strExt

SaveFileDialog1.Filter = strExt & " Image Files|*." + strExt

SaveFileDialog1.FilterIndex = 1

If SaveFileDialog1.ShowDialog() = DialogResult.OK Then

If (SaveFileDialog1.FileName = "") Then

Return

Else

' save the file with the name supplied by the user

picContainer.Image.Save(SaveFileDialog1.FileName)

End If

' update the current image file to point to the newly saved

' image

CurrentFile = SaveFileDialog1.FileName

Me.Text = "Watermark Utility: " + CurrentFile

MessageBox.Show(CurrentFile.ToString() + " saved.", "File

Save")

Else

MessageBox.Show("The save file request was cancelled by

user.", "Save Cancelled")

End If

Catch ex As Exception

MessageBox.Show(ex.Message.ToString(), "Image Save Error")

End Try

End Sub

#End Region

After handling the file IO operations, the next region of code is the Image Format Conversion section. In this region, the methods provided are used to convert the open image into an alternative format (e.g., bitmap to JPEG, or JPEC to GIF, etc.). Each section of code is annotated and may be reviewed in the following:

#Region "Image Format Conversion"

Private Function GetEncoderInfo(ByVal mimeType As String) As ImageCodecInfo

Dim j As Integer

Dim encoders As ImageCodecInfo()

encoders = ImageCodecInfo.GetImageEncoders()

For j = 0 To encoders.Length

If (encoders(j).MimeType = mimeType) Then

Return encoders(j)

End If

Return Nothing

End Function

Private Sub bitmapToolStripMenuItem_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles bitmapToolStripMenuItem.Click

' create a new name with the bitmap extension

Dim newName As String = _

System.IO.Path.GetFileNameWithoutExtension(CurrentFile)

newName = newName + ".bmp"

Try

' save the file as a bitmap

img.Save(newName, ImageFormat.Bmp)

CurrentFile = newName

picContainer.Image = Image.FromFile(CurrentFile)

Me.Text = "Watermark Utility: " + CurrentFile.ToString()

Catch

MessageBox.Show("Failed to save image to bitmap.", "Error", _

MessageBoxButtons.OK, MessageBoxIcon.Error)

Return

End Try

MessageBox.Show("Image file saved to " + newName.ToString(), _"Image Saved", MessageBoxButtons.OK,

MessageBoxIcon.Information)

End Sub

Private Sub emfToolStripMenuItem_Click(ByVal sender As System.Object, _ByVal e As System.EventArgs) Handles

emfToolStripMenuItem.Click

' create a new name with the emf extension

Dim newName As String = _

System.IO.Path.GetFileNameWithoutExtension(CurrentFile)

newName = newName + ".emf"

Try

' save the file as a EMF

img.Save(newName, ImageFormat.Emf)

CurrentFile = newName

picContainer.Image = Image.FromFile(CurrentFile)

Me.Text = "Watermark Utility: " + CurrentFile.ToString()

Catch

MessageBox.Show("Failed to save image to EMF.", "Error", _

MessageBoxButtons.OK, MessageBoxIcon.Error)

Return

End Try

MessageBox.Show("Image file saved to " + newName.ToString(), _"Image Saved", MessageBoxButtons.OK, MessageBoxIcon.Information)

End Sub

Private Sub exifToolStripMenuItem_Click(ByVal sender As System.Object, _ByVal e As System.EventArgs) Handles

exifToolStripMenuItem.Click

' create a new name with the EXIF extension

Dim newName As String = _

System.IO.Path.GetFileNameWithoutExtension(CurrentFile)

newName = newName + ".exif"

Try

' save the file as a EXIF

img.Save(newName, ImageFormat.Exif)

CurrentFile = newName

picContainer.Image = Image.FromFile(CurrentFile)

Me.Text = "Watermark Utility: " + CurrentFile.ToString()

Catch

MessageBox.Show("Failed to save image to EXIF.", "Error", _

MessageBoxButtons.OK, MessageBoxIcon.Error)

Return

End Try

MessageBox.Show("Image file saved to " + newName.ToString(), _"Image Saved", MessageBoxButtons.OK,

MessageBoxIcon.Information)

End Sub

Private Sub gIFFileToolStripMenuItem_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles

gIFFileToolStripMenuItem.Click

' create a new name with the GIF extension

Dim newName As String = _

System.IO.Path.GetFileNameWithoutExtension(CurrentFile)

newName = newName + ".gif"

Try

' save the file as a GIF

img.Save(newName, ImageFormat.Gif)

CurrentFile = newName

picContainer.Image = Image.FromFile(CurrentFile)

Me.Text = "Watermark Utility: " + CurrentFile.ToString()

Catch

MessageBox.Show("Failed to save image to GIF.", "Error", _

MessageBoxButtons.OK, MessageBoxIcon.Error)

Return

End Try

MessageBox.Show("Image file saved to " + newName.ToString(), _"Image Saved", MessageBoxButtons.OK, MessageBoxIcon.Information)

End Sub

Private Sub jPEGFileToolStripMenuItem_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles

jPEGFileToolStripMenuItem.Click

' create a new name with the JPEG extension

Dim newName As String = _

System.IO.Path.GetFileNameWithoutExtension(CurrentFile)

newName = newName + ".jpg"

Try

' save the file as a JPG

img.Save(newName, ImageFormat.Jpeg)

CurrentFile = newName

picContainer.Image = Image.FromFile(CurrentFile)

Me.Text = "Watermark Utility: " + CurrentFile.ToString()

Catch

MessageBox.Show("Failed to save image to JPEG.", "Error", _

MessageBoxButtons.OK, MessageBoxIcon.Error)

Return

End Try

MessageBox.Show("Image file saved to " + newName.ToString(), _"Image Saved", MessageBoxButtons.OK, MessageBoxIcon.Information)

End Sub

Private Sub pNGFileToolStripMenuItem_Click(ByVal sender As System.Object,ByVal e As System.EventArgs) Handles pNGFileToolStripMenuItem.Click

' create a new name with the PNG extension

Dim newName As String = _

System.IO.Path.GetFileNameWithoutExtension(CurrentFile)

newName = newName + ".png"

Try

' save the file as a png

img.Save(newName, ImageFormat.Png)

CurrentFile = newName

picContainer.Image = Image.FromFile(CurrentFile)

Me.Text = "Watermark Utility: " + CurrentFile.ToString()

Catch

MessageBox.Show("Failed to save image to PNG.", "Error", _

MessageBoxButtons.OK, MessageBoxIcon.Error)

Return

End Try

MessageBox.Show("Image file saved to " + newName.ToString(), _"Image Saved", MessageBoxButtons.OK, MessageBoxIcon.Information)

End Sub

Private Sub tIFFFileToolStripMenuItem_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles

tIFFFileToolStripMenuItem.Click

' create a new name with the tif extension

Dim newName As String = _

System.IO.Path.GetFileNameWithoutExtension(CurrentFile)

newName = newName + ".tif"

Try

' save the file as a tif

img.Save(newName, ImageFormat.Tiff)

CurrentFile = newName

picContainer.Image = Image.FromFile(CurrentFile)

Me.Text = "Watermark Utility: " + CurrentFile.ToString()

Catch

MessageBox.Show("Failed to save image to TIF.", "Error", _

MessageBoxButtons.OK, MessageBoxIcon.Error)

Return

End Try

MessageBox.Show("Image file saved to " + newName.ToString(), _"Image Saved", MessageBoxButtons.OK, MessageBoxIcon.Information)

End Sub

Private Sub windowsMetafileToolStripMenuItem_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles

windowsMetafileToolStripMenuItem.Click

' create a new name with the WMF extension

Dim newName As String = _

System.IO.Path.GetFileNameWithoutExtension(CurrentFile)

newName = newName + ".wmf"

Try

' save the file as a WMF

img.Save(newName, ImageFormat.Wmf)

CurrentFile = newName

picContainer.Image = Image.FromFile(CurrentFile)

Me.Text = "Watermark Utility: " + CurrentFile.ToString()

Catch

MessageBox.Show("Failed to save image to WMF.", "Error", _

MessageBoxButtons.OK, MessageBoxIcon.Error)

Return

End Try

MessageBox.Show("Image file saved to " + newName.ToString(), _"Image Saved", MessageBoxButtons.OK, MessageBoxIcon.Information)

End Sub

#End Region

Following the image conversion routines, the next region of code is used to perform the actual water marking functions.

#Region "Watermarking"

''' <summary>

''' Display the watermark as it would appear after

''' the watermark were saved to the file

''' </summary>

''' <remarks></remarks>

Private Sub btnPreview_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnPreview.Click

' Update the applicaton by reloading the image

picContainer.Image = Image.FromFile(CurrentFile)

Dim opac As Integer = 0

Dim sOpacity As String = cboOpacity.Text

' Determine the opacity of the watermark

Select Case (sOpacity)

Case "100%"

opac = 255 ' 1 * 255

Case "75%"

opac = 191 ' .75 * 255

Case "50%"

opac = 127 ' .5 * 255

Case "25%"

opac = 64 ' .25 * 255

Case "10%"

opac = 25 ' .10 * 255

Case Else

opac = 127 ' default at 50%; .5 * 255

End Select

' Get a graphics context

Dim g As Graphics = Graphics.FromImage(picContainer.Image)

' Create a solid brush to write the watermark text on the image

Dim myBrush As Brush

myBrush = New SolidBrush(Color.FromArgb(opac, myWatermarkColor))

' Calculate the size of the text

Dim sz As SizeF = g.MeasureString(txtWaterMark.Text, myFont)

' Creae a copy of variables to keep track of the

' drawing position (X,Y)

Dim X As Integer

Dim Y As Integer

' Set the drawing position based on the users

' selection of placing the text at the bottom or

' top of the image

If (optTop.Checked = True) Then

X = Convert.ToInt32((picContainer.Image.Width - sz.Width) / 2)

Y = Convert.ToInt32((picContainer.Top + sz.Height) / 2)

Else

X = Convert.ToInt32((picContainer.Image.Width - sz.Width) / 2)

Y = Convert.ToInt32((picContainer.Image.Height - sz.Height))

End If

' draw the water mark text

g.DrawString(txtWaterMark.Text, myFont, myBrush, New Point(X, Y))

End Sub

Private Sub btnFont_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnFont.Click

' default the current font and color to that

' used in the watermark textbox

fontDialog1.ShowColor = True

fontDialog1.Font = txtWaterMark.Font

fontDialog1.Color = txtWaterMark.ForeColor

If fontDialog1.ShowDialog() <> DialogResult.Cancel Then

myFont = fontDialog1.Font

myWatermarkColor = fontDialog1.Color

txtWaterMark.Font = fontDialog1.Font

txtWaterMark.ForeColor = fontDialog1.Color

End If

End Sub

#End Region

That wraps up the sum of the code needed to drive the Watermarking utility. With the code provided, it is possible to convert from one image format to another and to apply a user defined watermark on an existing image file.

Summary

While this article was written to demonstrate an approach to watermarking an image file in the context of a Win Foms utility application; the code used in the project could be modified to batch process image files, or to watermark image files programmatically and without user intervention. Even used as a utility, the application could have some value to anyone wishing to watermark or caption an image file before exposing the image file on the web.