Ошибка перезаписи файла: В GDI+ возникла ошибка общего вида

    Private Sub Button2_Click(sender As System.Object, e As EventArgs) Handles Button2.Click
        SaveFileDialog1.Filter = "Image bmp|*.bmp"
        If SaveFileDialog1.ShowDialog = DialogResult.Cancel Then Exit Sub
        bmp.Save(SaveFileDialog1.FileName)
    End Sub

[SPOILER]Public Class Form1
    Dim Pen1 As New Pen(Color.Black, 3)
    Dim bmp As Bitmap
    Dim g, grap As Graphics
    Dim x As Long, y As Long
    Dim IsOpened, drawing
 
    Private Sub Button1_Click(sender As System.Object, e As EventArgs) Handles Button1.Click
        OpenFileDialog1.Filter = "Image bmp|*.bmp"
        If OpenFileDialog1.ShowDialog = DialogResult.Cancel Then Exit Sub
        PictureBox1.Image = Image.FromFile(OpenFileDialog1.FileName)
        Me.Text = (OpenFileDialog1.SafeFileName & " - Paint")
        Load_P()
        'Рисуем заданое изображение
        g.DrawImage(New Bitmap(OpenFileDialog1.FileName), 0, 0)
        grap.DrawImage(New Bitmap(OpenFileDialog1.FileName), 0, 0)
        PictureBox1.Image = bmp
    End Sub
 
    Private Sub Button2_Click(sender As System.Object, e As EventArgs) Handles Button2.Click
        SaveFileDialog1.Filter = "Image bmp|*.bmp"
        If SaveFileDialog1.ShowDialog = DialogResult.Cancel Then Exit Sub
        ' bmp.Dispose()
        bmp.Save(SaveFileDialog1.FileName)
    End Sub
 
    Private Sub PictureBox1_MouseDown(sender As Object, e As MouseEventArgs) Handles PictureBox1.MouseDown
        x = e.X
        y = e.Y
        drawing = True
    End Sub
 
    Private Sub PictureBox1_MouseUp(sender As Object, e As MouseEventArgs) Handles PictureBox1.MouseUp
        drawing = False
    End Sub
    Private Sub PictureBox1_MouseMove(sender As Object, e As MouseEventArgs) Handles PictureBox1.MouseMove
        If IsOpened = False And e.Button = Windows.Forms.MouseButtons.Left And CheckBox1.Checked Then Form2.Visible = True
        If e.Button = Windows.Forms.MouseButtons.Left And IsOpened And CheckBox1.Checked Then
            g.DrawLine(Pen1, e.X, e.Y, x, y)
            grap.DrawLine(Pen1, e.X, e.Y, x, y)
            PictureBox1.Image = bmp
            x = e.X
            y = e.Y
        End If
    End Sub
 
    Private Sub TrackBar1_Scroll(sender As System.Object, e As EventArgs) Handles TrackBar1.Scroll
        Pen1.Width = TrackBar1.Value
    End Sub
    Private Sub Button3_Click(sender As System.Object, e As EventArgs) Handles Button3.Click
        If ColorDialog1.ShowDialog = DialogResult.Cancel Then Exit Sub
        Pen1.Color = ColorDialog1.Color
    End Sub
 
    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
    End Sub
 
    Private Sub CheckBox1_CheckedChanged(sender As Object, e As EventArgs) Handles CheckBox1.CheckedChanged
    End Sub
 
    Public Sub Load_P()
        bmp = New Bitmap(PictureBox1.Width, PictureBox1.Height)
        g = Graphics.FromImage(bmp)
        grap = PictureBox1.CreateGraphics
        Pen1.StartCap = Drawing2D.LineCap.Round
        Pen1.EndCap = Drawing2D.LineCap.Round
        IsOpened = True
        Button2.Visible = True
    End Sub
 
    Private Sub Button4_Click(sender As Object, e As EventArgs) Handles Button4.Click
        PictureBox1.Image = Image.FromFile("D:\1\empty.bmp")
        Load_P()
        Me.Text = ("No name - Paint")
        g.DrawImage(New Bitmap("D:\1\empty.bmp"), 0, 0)
        grap.DrawImage(New Bitmap("D:\1\empty.bmp"), 0, 0)
        PictureBox1.Image = bmp
    End Sub
 
    Private Sub PictureBox1_Click(sender As Object, e As EventArgs) Handles PictureBox1.Click
    End Sub
End Class
[/SPOILER]

grap.DrawImage(New Bitmap(OpenFileDialog1.FileName), 0, 0)
 grap = PictureBox1.CreateGraphics

Dim oBitmap As Bitmap
oBitmap = New Bitmap("c:\\example.jpg")
Dim oGraphic As Graphics
' Here create a new bitmap object of the same height and width of the image.
Dim bmpNew As Bitmap = New Bitmap(oBitmap.Width, oBitmap.Height)
oGraphic = Graphics.FromImage(bmpNew)
oGraphic.DrawImage(oBitmap, New Rectangle(0, 0, _
bmpNew.Width, bmpNew.Height), 0, 0, oBitmap.Width, _
oBitmap.Height, GraphicsUnit.Pixel)
' Release the lock on the image file. Of course,
' image from the image file is existing in Graphics object
oBitmap.Dispose()
oBitmap = bmpNew
 
Dim oBrush As New SolidBrush(Color.Black)
Dim ofont As New Font("Arial", 8 )
oGraphic.DrawString("Some text to write", ofont, oBrush, 10, 10)
oGraphic.Dispose()
ofont.Dispose()
oBrush.Dispose()
oBitmap.Save("c:\\example.jpg", ImageFormat.Jpeg)
oBitmap.Dispose()