Thread time out in DO while loop of a picturebox

See more:

VB

i used do while loop for print RGB value of the picture in picture box.it print RGB value for small picture height and width.if i use large size picture it not responding or thread time 60 minutes out.Give some program code to print HIGH width and height picture RGB value with out not respond or Quick......my code is

Private Sub btn_getPixels_Click(ByVal sender As Object, ByVal e As EventArgs)
        listBox1.Items.Add("Pixel             Color")
        Try 
            Dim img As Bitmap = New Bitmap(pictureBox1.Image)
            Dim c As Color
            Dim i As Integer = 0
            Do While (i < img.Width)
                Dim j As Integer = 0
                Do While (j < img.Height)
                    c = img.GetPixel(i, j)
                    listBox1.Items.Add((i.ToString + (","  _
                                    + (j.ToString + ("             " + c.Name)))))
                    j = (j + 1)
                Loop
                i = (i + 1)
            Loop
        Catch ex As Exception
            MessageBox.Show(ex.Message)
        End Try
    End Sub