I need to load up an image and draw a draggable rectangle on it to determine the area to resize

I assume this is WinForms?...what version VB.Net are you working in?

Wow...Genius!!!!

Hmmm... I can load up the picture but that red rectangle is not showing in the picturebox1... I am using VS2010 and winform....

My bad, I noticed that if the picture is too big, I cant really crop it to 300x300. In that case can I do a resize of the source picture to 500x500 into picturebox1?

Sorry for the trouble

The red rectangle is being drawn here:

    Private Sub PictureBox1_Paint(ByVal sender As Object, ByVal e As System.Windows.Forms.PaintEventArgs) Handles PictureBox1.Paint
        Using dashes As New Pen(Color.Red)
            dashes.DashStyle = Drawing2D.DashStyle.Dash
            e.Graphics.DrawRectangle(dashes, CropRC)
        End Using
    End Sub

Make sure you haven't somehow lost the "Handles PictureBox1.Paint" part on the end of the first line.

Can you explain more how you want to handle large images?
...are your source images always "square"?
...if they are bigger than 500x500 then you want them shrunk down to 500x500 BEFORE being displayed in PictureBox1?
...an alternative is to allow SCROLLING in PictureBox1...

I copied everything from the code above so I dun think I have missed that out :)

I wun know what would be the source file size is like cuz I was testing it with a relative large file and I noticed that problem. So I was thinking since the end results is a 300x300 and 100x100 thumbnail, wouldn it be better if I can straightaway resize it to 500x500?

Oh, the button2 (I assume is crop) is not transferring to the picturebox2 as well although the trace went well...

Even doing a picturebox1.refresh does not show the red rectangle.

I wrote it in VS2010 as well...not sure where the difference is...

We can certainly crop to 500x500 beforehand but I would like to solve the other problem first.

Make sure the controls are all named the same.  I have PictureBox1, PictureBox2, Button1, Button2

Also make sure the SizeMode of both PictureBoxes is set to "Normal".

If that doesn't fix it then post the code from YOUR form and maybe we'll be able to spot the difference...    ?

I was thinking of doing something like this.


sample.jpg

my code

Public Class Form1

    Private StartPT As Point
    Private CropRC As Rectangle
    Private CropSize As New Size(300, 300)
    Private DestinationSize As New Size(100, 100)

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs)
        CropRC = New Rectangle(New Point(PictureBox1.Width / 2 - CropSize.Width / 2, PictureBox1.Height / 2 - CropSize.Height / 2), CropSize)
    End Sub

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Using ofd As New OpenFileDialog
            ofd.Title = "Select an Image"
            ofd.Filter = "Image Files(*.BMP;*.JPG;*.GIF)|*.BMP;*.JPG;*.GIF|All files (*.*)|*.*"
            If ofd.ShowDialog = Windows.Forms.DialogResult.OK Then
                Try
                    ' this technique opens the image without locking the file:
                    Using fs As New System.IO.FileStream(ofd.FileName, IO.FileMode.Open)
                        PictureBox1.Image = Image.FromStream(fs)

                    End Using
                Catch ex As Exception
                    MessageBox.Show("File: " & ofd.FileName & vbCrLf & vbCrLf & ex.ToString, "Error Opening Image", MessageBoxButtons.OK, MessageBoxIcon.Error)
                End Try
            End If
        End Using
    End Sub

    Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
        If Not IsNothing(PictureBox1.Image) Then
            Dim bmp As New Bitmap(DestinationSize.Width, DestinationSize.Height)
            Using G As Graphics = Graphics.FromImage(bmp)
                Dim destPTs() As Point = {New Point(0, 0), New Point(DestinationSize.Width, 0), New Point(0, DestinationSize.Height)}
                G.DrawImage(PictureBox1.Image, destPTs, CropRC, GraphicsUnit.Pixel)
            End Using
            PictureBox2.Image = bmp
        End If
    End Sub

    Private Sub PictureBox1_Paint(ByVal sender As Object, ByVal e As System.Windows.Forms.PaintEventArgs) Handles PictureBox1.Paint

        Using dashes As New Pen(Color.Red)
            dashes.DashStyle = Drawing2D.DashStyle.Dash
            e.Graphics.DrawRectangle(dashes, CropRC)
        End Using
    End Sub

    Private Sub PictureBox1_MouseDown(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles PictureBox1.MouseDown
        If e.Button = Windows.Forms.MouseButtons.Left Then
            StartPT = New Point(e.X, e.Y)
            Cursor.Clip = PictureBox1.RectangleToScreen(PictureBox1.ClientRectangle)
        End If
    End Sub

    Private Sub PictureBox1_MouseMove(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles PictureBox1.MouseMove
        If e.Button = Windows.Forms.MouseButtons.None Then
            PictureBox1.Cursor = IIf(CropRC.Contains(e.X, e.Y), Cursors.SizeAll, Cursors.Default)
        ElseIf e.Button = Windows.Forms.MouseButtons.Left AndAlso PictureBox1.Cursor = Cursors.SizeAll Then
            CropRC.Offset(e.X - StartPT.X, e.Y - StartPT.Y)
            If CropRC.Location.X < 0 Then
                CropRC.Location = New Point(0, CropRC.Location.Y)
            End If
            If CropRC.Location.Y < 0 Then
                CropRC.Location = New Point(CropRC.Location.X, 0)
            End If
            If CropRC.Right > PictureBox1.ClientRectangle.Right - 1 Then
                CropRC.Location = New Point(PictureBox1.ClientRectangle.Width - CropSize.Width - 1, CropRC.Location.Y)
            End If
            If CropRC.Bottom > PictureBox1.ClientRectangle.Bottom - 1 Then
                CropRC.Location = New Point(CropRC.Location.X, PictureBox1.ClientRectangle.Height - CropSize.Height - 1)
            End If
            StartPT = New Point(e.X, e.Y)
            PictureBox1.Refresh()
        End If
    End Sub

    Private Sub PictureBox1_MouseUp(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles PictureBox1.MouseUp
        Cursor.Clip = Nothing
    End Sub

End Class

Select allOpen in new window

Alright man!!!!  I recopied the code and it works now!!!

Genius!!!

Glad you got it working!...  =)

Oppps btw how do I dynamically resize the image in picturebox1 if it is too big? Lets say I put a textbox and input a value of 10 which stands for 10% downsize?