Line drawing on picturebox

[cyphixation]

Hi guys. im pretty new to vb.net and graphics programming and have a form with a picturebox and one button. im just wanting to draw a few lines from where the mouse button goes down to where it comes up.

The pic stays white the whole time in run mode, but stopping at a breakpoint at the end of PictureBox1_MouseUp() in debug, i can see the lines.

Can someone help me out and more so point me to tutorial sites on vb.net graphics? The code is below.

Public Class Form1
    Inherits System.Windows.Forms.Form
    Dim big_G As Graphics
    Dim pen As New pen(Red)
    Dim x1, y1, x2, y2 As Integer
    Dim DRAW As Boolean
    Public Const YES As Boolean = True
    Public Const NO As Boolean = False


    Private Sub image_new_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) _
                                Handles image_new.Click
        Dim bmp As Bitmap
        Dim G As Graphics

        bmp = New Bitmap(PictureBox1.Width, PictureBox1.Height)
        PictureBox1.Image = bmp
        G = Graphics.FromImage(bmp)
        G.Clear(White)

        big_G = G
    End Sub


    Private Sub PictureBox1_MouseDown(ByVal sender As System.Object, ByVal e As System.Windows.Forms.MouseEventArgs) _
                                      Handles PictureBox1.MouseDown
        x1 = e.X
        y1 = e.Y
        DRAW = YES
    End Sub

    Private Sub PictureBox1_MouseUp(ByVal sender As System.Object, ByVal e As System.Windows.Forms.MouseEventArgs) _
                                      Handles PictureBox1.MouseUp
        x2 = e.X
        y2 = e.Y

        If (DRAW) Then
            big_G.DrawLine(pen, x1, y1, x2, y2)
            DRAW = NO
        End If
    End Sub
End Class

Sorry, im not sure how to correctly post code here either

 

[ballisticnylon]

Try setting big_G equal to the graphics object of the PictureBox.

[VB]
Dim big_G As Graphics = PictureBox1.CreateGraphics
[/VB]

 

[cyphixation]

...works like a dream. Thank you very much...off to read more on CreateGraphics

 

[cyphixation]

damn...well, it doesnt repaint itself if min/maxed or covered with another app. i supose i have more reading to do, but thank you very much for the start

 

[Hamburger1984]

I got it working.....
Hope this helps!

Public Class Form1
    Inherits System.Windows.Forms.Form

    Dim bmp As Bitmap
    Dim big_G As Graphics
    Dim pen As New Pen(Color.Red)
    Dim x1, y1, x2, y2 As Integer
    Dim DRAW As Boolean
    Public Const YES As Boolean = True
    Public Const NO As Boolean = False

    Private Sub image_new_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) _
    Handles image_new.Click
        Dim G As Graphics
        bmp = New Bitmap(PictureBox1.Width, PictureBox1.Height)
        PictureBox1.Image = bmp
        G = Graphics.FromImage(bmp)
        G.Clear(Color.White)
        big_G = G
    End Sub

    Private Sub PictureBox1_MouseDown(ByVal sender As System.Object, ByVal e As System.Windows.Forms.MouseEventArgs) _
    Handles PictureBox1.MouseDown
        x1 = e.X
        y1 = e.Y
        DRAW = YES
    End Sub

    Private Sub PictureBox1_MouseUp(ByVal sender As System.Object, ByVal e As System.Windows.Forms.MouseEventArgs) _
    Handles PictureBox1.MouseUp
        x2 = e.X
        y2 = e.Y
        If (DRAW) Then
            big_G.DrawLine(pen, x1, y1, x2, y2)
            DRAW = NO
            PictureBox1.Image = Nothing
            PictureBox1.Image = bmp
        End If
    End Sub

End Class

 

[Hamburger1984]

.....and if you dont want to use the Bitmap and PictureBox method you should take a look at the Controls "Paint" event! this is the place where all the drawing is done normally....