Comparing two Images

Few days back I was looking to compare two image and find difference between them in WPF. After searching and reading few articles I realized that comparing two image and find difference is much easier using methods of Graphics Class (i.e. using GDI+).  So I decide to compare and find difference between two images using GDI+ and then convert into a BitmapImage. For faster comparing we have to use pointer and write code in unsafe block. As pointer and unsafe block are not supported in VB.NET so comparing code has to be in C# or C++.

Code

public static Bitmap BitmapDifference(Bitmap first, Bitmap second)
        {
            BitmapData data1 = first.LockBits(new Rectangle(0, 0, first.Width, first.Height), ImageLockMode.ReadWrite, first.PixelFormat);
            BitmapData data2 = second.LockBits(new Rectangle(0, 0, second.Width, second.Height), ImageLockMode.ReadWrite, second.PixelFormat);
            Bitmap bmpresult = new Bitmap(first.Width, first.Height);

            BitmapData data3 = bmpresult.LockBits(new Rectangle(0, 0, bmpresult.Width, bmpresult.Height), ImageLockMode.ReadWrite, first.PixelFormat);

            unsafe
            {
                int remain1 = data1.Stride - data1.Width * 3;
                int remain2 = data2.Stride - data2.Width * 3;
                int remain3 = data3.Stride - data3.Width * 3;

                byte* ptr1 = (byte*)data1.Scan0;
                byte* ptr2 = (byte*)data2.Scan0;
                byte* ptr3 = (byte*)data3.Scan0;

                for (int i = 0; i < first.Height; i++)
                {
                    for (int j = 0; j < first.Width * 3; j++)
                    {
                        byte ac = (byte)(Math.Abs(ptr1[0] - ptr2[0]));
                        if (ac < 15)
                        {
                            //Change Pixel Color to Black for all the pixel whose value is
                            ptr3[0] = 0;
                        }
                        else
                        {
                            ptr3[0] = ac;
                        }
                        ptr1++;
                        ptr2++;
                        ptr3++;
                    }
                    ptr1 += remain1;
                    ptr2 += remain2;
                    ptr3 += remain3;
                }
            }
            first.UnlockBits(data1);
            second.UnlockBits(data2);
            bmpresult.UnlockBits(data3);

            bmpresult.MakeTransparent(Color.Black);
            return bmpresult;
        }

Above function will return the difference between two images using following code 

public void GetDifference()
{
    Bitmap bmp1 = new Bitmap(@"C:\1.jpg");
    Bitmap bmp2 = new Bitmap(@"C:\2.jpg");
    Bitmap result = BitmapDifference(bmp1, bmp2);
    result.Save(@"C:\new.jpg");
}

Sender Property of MailMessage

Many of the time we need to send email on behalf of someone else. For Example, all the employees in the company sending email on behalf of the company. Another common example is invitation email send to the friends by the website on behalf of its user. We have two properties available in MailMessage Class in .NET which are From and Sender which by definition looks very similar but they are different.

When sending a email From Property will contain the Email Address on behalf of whom we are sending the email and Sender property will be the person who is sending the email. Sender is an optional property and is used when we need to send email on behalf of someone else. When we are sending an email  which require authentication (i.e. Credentials) and our MailMessage has Sender property assigned, then Username of NetworkCredential will be same as Sender Email Address.  Below is the code of how we can use it.

Dim msg As New MailMessage
msg.From = New MailAddress("from@domain.com")
msg.Sender = New MailAddress("sender@domain.com")
msg.Subject = "Test Email"
msg.Body = "Hello World. This is a Test Email"

Dim client As New SmtpClient("Host Address", "Port Number")
client.Credentials = New NetworkCredential(msg.Sender.Address, "Password")
client.Send(msg)

Note: Although I have not tested on other SSL Enabled email provider but Sender Property doesn’t work with Gmail. So I think if Smtp Server requires SSL then Sender Property might not work.

Print Multiple-layered column header in datagridview

Recently someone had asked a question on a forum of “How to create multiple-layered column header in datagridview and also have a print preview of it in vb.net”. Creating multiple-layered column header is available on “Windows Forms Data Controls and Data Binding Forum FAQ” on MSDN Forum but the code is provided in VC#. So I have created a code in VB.NET through which multiple-layered column header can be created as well we can have print preview of it.

Multiple-layered Column Header DatagridView

To create a datagridview with multiple column header we have to handle the DataGridView.Painting and DataGridView.CellPainting events, so that we can draw header as we want. We can use PrintPage event of PrintDocument to build the page for printing.

Print Preview of Multi-layered Column Datagridview

Code for Datagridview

Imports System.Drawing.Printing
Public Class DemoForm
    Dim names() As String = {"Microsoft", "Adobe", "SUN"}
    Dim WithEvents MyPrintDocument As New PrintDocument
    Private Sub DemoForm_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        Me.DataGridView1.Columns.Add("clmProduct1", "Product")
        Me.DataGridView1.Columns.Add("clmPrice1", "Price")
        Me.DataGridView1.Columns.Add("clmProduct2", "Product")
        Me.DataGridView1.Columns.Add("clmPrice2", "Price")
        Me.DataGridView1.Columns.Add("clmProduct3", "Product")
        Me.DataGridView1.Columns.Add("clmPrice3", "Price")
        DataGridView1.ColumnHeadersHeightSizeMode = DataGridViewColumnHeadersHeightSizeMode.EnableResizing
        DataGridView1.ColumnHeadersHeight = DataGridView1.ColumnHeadersHeight * 2
        DataGridView1.ColumnHeadersDefaultCellStyle.Alignment = DataGridViewContentAlignment.BottomCenter
    End Sub
    Private Sub DataGridView1_Paint(ByVal sender As Object, ByVal e As System.Windows.Forms.PaintEventArgs) Handles DataGridView1.Paint
        For i As Integer = 0 To 5 Step 2
            Dim rec As Rectangle = DataGridView1.GetCellDisplayRectangle(i, -1, True)
            rec.X += 1
            rec.Y += 1
            rec.Width = rec.Width * 2 - 2
            rec.Height = rec.Height / 2 - 2
            e.Graphics.FillRectangle(New SolidBrush(Me.DataGridView1.ColumnHeadersDefaultCellStyle.BackColor), rec)
            Dim format As New StringFormat
            format.Alignment = StringAlignment.Center
            format.LineAlignment = StringAlignment.Center
            e.Graphics.DrawString(names(i / 2), DataGridView1.ColumnHeadersDefaultCellStyle.Font, New SolidBrush(DataGridView1.ColumnHeadersDefaultCellStyle.ForeColor), rec, format)
        Next
    End Sub
    Private Sub DataGridView1_CellPainting(ByVal sender As Object, ByVal e As System.Windows.Forms.DataGridViewCellPaintingEventArgs) Handles DataGridView1.CellPainting
        If e.RowIndex = -1 And e.ColumnIndex <> -1 Then
            e.PaintBackground(e.CellBounds, False)
            Dim rec As Rectangle = e.CellBounds
            rec.Y += e.CellBounds.Height / 2
            rec.Height = e.CellBounds.Height / 2
            e.PaintContent(rec)
            e.Handled = True
        End If
    End Sub

    Private Sub btnPrint_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnPrint.Click
        Dim dg As New PrintPreviewDialog
        dg.Document = MyPrintDocument
        dg.ShowDialog()
    End Sub

    Private Sub PrintDocument1_PrintPage(ByVal sender As System.Object, ByVal e As System.Drawing.Printing.PrintPageEventArgs) Handles MyPrintDocument.PrintPage
        Dim leftMargin As Integer = 10
        Dim position As Integer = leftMargin
        Dim yPosition As Integer
        Dim height As Integer = DataGridView1.ColumnHeadersHeight / 2
        yPosition = 0
        For i As Integer = 0 To 5 Step 2
            Dim totalWidth As Double = DataGridView1.Columns(i).Width + DataGridView1.Columns(i + 1).Width
            e.Graphics.FillRectangle(New SolidBrush(Color.LightGray), New Rectangle(position, yPosition, totalWidth, height))
            e.Graphics.DrawRectangle(Pens.Black, New Rectangle(position, yPosition, totalWidth, height))
            Dim format As New StringFormat
            format.Alignment = StringAlignment.Center
            format.LineAlignment = StringAlignment.Center
            e.Graphics.DrawString(names(i / 2), New Font("Arial", 12, FontStyle.Bold), Brushes.Black, position, yPosition)
            position = position + totalWidth
        Next

        position = leftMargin
        yPosition = DataGridView1.ColumnHeadersHeight / 2
        For Each dr As DataGridViewColumn In DataGridView1.Columns
            Dim totalWidth As Double = dr.Width
            e.Graphics.FillRectangle(New SolidBrush(Color.LightGray), New Rectangle(position, yPosition, totalWidth, height))
            e.Graphics.DrawRectangle(Pens.Black, New Rectangle(position, yPosition, totalWidth, height))
            e.Graphics.DrawString(dr.HeaderText, New Font("Arial", 12, FontStyle.Bold), Brushes.Black, position, yPosition)
            position = position + totalWidth
        Next

        For Each dr As DataGridViewRow In DataGridView1.Rows
            position = leftMargin
            yPosition = yPosition + DataGridView1.ColumnHeadersHeight / 2
            For Each dc As DataGridViewCell In dr.Cells
                Dim totalWidth As Double = dc.OwningColumn.Width
                e.Graphics.FillRectangle(New SolidBrush(Color.White), New Rectangle(position, yPosition, totalWidth, height))
                e.Graphics.DrawRectangle(Pens.Black, New Rectangle(position, yPosition, dc.OwningColumn.Width, height))
                e.Graphics.DrawString(dc.Value, New Font("Arial", 12, FontStyle.Regular), Brushes.Black, position, yPosition)
                position = position + totalWidth
            Next
        Next
    End Sub

End Class

Gaurav Khanna – Microsoft MVP 2010

I am proud to announce that I am awarded Microsoft MVP on January 01, 2010 for providing technical expertise in Visual Basic technical communities for past one year.

About the MVP Award Program (As described by microsoft)

Since the early 1990s, Microsoft has recognized the inspiring activities of MVPs around the world with the MVP Award. MVPs freely share their deep knowledge, real-world experience, and impartial, objective feedback to help people enhance the way they use technology. Of more than 100 million users who participate in technology communities, around 4,000 are recognized as Microsoft MVPs.

MVPs make exceptional contributions to technical communities, sharing their passion, knowledge, and know-how. Meanwhile, because MVPs hear the opinions and needs of many others in the technical community, they are well-placed to share highly focused feedback with Microsoft.

MVPs are independent experts who are offered a close connection with people at Microsoft. To acknowledge MVPs’ leadership and provide a platform to help support their efforts, Microsoft often gives MVPs early access to Microsoft products, as well as the opportunity to pass on their highly targeted feedback and recommendations about product design, development, and support.

Email from Microsoft

Dear Gaurav Khanna,

Congratulations! We are pleased to present you with the 2010 Microsoft® MVP Award! This award is given to exceptional technical community leaders who actively share their high quality, real world expertise with others. We appreciate your outstanding contributions in Visual Basic technical communities during the past year.

The Microsoft MVP Award provides us the unique opportunity to celebrate and honor your significant contributions and say “Thank you for your technical leadership.”

Toby Richards
General Manager
Community & Online Support

List of MVPs announced from South Asia in January 2010 can be found on following link

http://blogs.technet.com/southasiamvp/archive/2010/01/03/new-mvps-announced-january-2010.aspx