Blur with LockBits not working?

I tried using LockBits to blur images, since I heard it was faster, and there's no error, but there's no blur either. It doesn't do anything. The commented-out code is the code I had before using LockBits, and it works.

vb.net Code:

Private Sub BlurImage(ByVal img As Bitmap, Optional ByVal radius As Integer = 3, Optional ByVal blur_bounds As Object = Nothing)
        Dim bb As Rectangle
        If blur_bounds IsNot Nothing Then
            bb = CType(blur_bounds, Rectangle)
        Else
            bb = New Rectangle(0, 0, img.Width, img.Height)
        End If
        Dim b_data As Drawing.Imaging.BitmapData = img.LockBits(bb, Imaging.ImageLockMode.ReadWrite, Imaging.PixelFormat.Format32bppArgb)
        Dim ptr As IntPtr = b_data.Scan0
        Dim bytes As Integer = b_data.Stride * b_data.Height
        Dim img_bytes(bytes - 1) As Byte
        System.Runtime.InteropServices.Marshal.Copy(ptr, img_bytes, 0, bytes)
        Dim i As Integer
        For i = 0 To radius
            Dim y, x As Integer
            For y = (bb.Y + 1) To bb.Bottom - 1
                For x = (bb.X + 1) To bb.Right - 1
                    Try
                        'Dim px_up As Color = img.GetPixel(x, y - 1)
                        'Dim px_down As Color = img.GetPixel(x, y + 1)
                        'Dim px_left As Color = img.GetPixel(x - 1, y)
                        'Dim px_right As Color = img.GetPixel(x + 1, y)
                        'Dim pxR As Integer = Average_Int(px_up.R, px_down.R, px_left.R, px_right.R) ', 90)
                        'Dim pxG As Integer = Average_Int(px_up.G, px_down.G, px_left.G, px_right.G) ', 90)
                        'Dim pxB As Integer = Average_Int(px_up.B, px_down.B, px_left.B, px_right.B) ', 90) '90s are added for "blackness"
                        'Dim n_px As Color = Color.FromArgb(255, pxR, pxG, pxB)
                        'img.SetPixel(x, y, n_px)
                        Dim px_up As Color = Color.FromArgb(img_bytes(((y - 1) * bb.Width + x) * 4), img_bytes(((y - 1) * bb.Width + x) * 4 + 1), img_bytes(((y - 1) * bb.Width + x) * 4 + 2), img_bytes(((y - 1) * bb.Width + x) * 4 + 3))
                        Dim px_down As Color = Color.FromArgb(img_bytes(((y + 1) * bb.Width + x) * 4), img_bytes(((y + 1) * bb.Width + x) * 4 + 1), img_bytes(((y + 1) * bb.Width + x) * 4 + 2), img_bytes(((y + 1) * bb.Width + x) * 4 + 3))
                        Dim px_left As Color = Color.FromArgb(img_bytes((y * bb.Width + (x - 1)) * 4), img_bytes((y * bb.Width + (x - 1)) * 4 + 1), img_bytes((y * bb.Width + (x - 1)) * 4 + 2), img_bytes((y * bb.Width + (x - 1)) * 4 + 3))
                        Dim px_right As Color = Color.FromArgb(img_bytes((y * bb.Width + (x + 1)) * 4), img_bytes((y * bb.Width + (x + 1)) * 4 + 1), img_bytes((y * bb.Width + (x + 1)) * 4 + 2), img_bytes((y * bb.Width + (x + 1)) * 4 + 3))
                        Dim pxR As Integer = Average_Int(px_up.R, px_down.R, px_left.R, px_right.R)
                        Dim pxG As Integer = Average_Int(px_up.G, px_down.G, px_left.G, px_right.G)
                        Dim pxB As Integer = Average_Int(px_up.B, px_down.B, px_left.B, px_right.B)
                        Dim n_px As Color = Color.FromArgb(255, pxR, pxG, pxB)
                        img_bytes((y * bb.Width + x) * 4) = n_px.A
                        img_bytes((y * bb.Width + x) * 4 + 1) = n_px.R
                        img_bytes((y * bb.Width + x) * 4 + 2) = n_px.G
                        img_bytes((y * bb.Width + x) * 4 + 3) = n_px.B
                    Catch ex As Exception
                        GoTo finish_sub
                    End Try
                Next
            Next
        Next
finish_sub:
        img.UnlockBits(b_data)
    End Sub

Oh, and I also did a test like this:

vb.net Code:

Public Class Form1
    Protected Overrides Sub OnPaint(ByVal e As System.Windows.Forms.PaintEventArgs)
        Dim g As Graphics = e.Graphics
        Dim img As Bitmap = My.Resources.test.Clone()
        LockBitsTest(img)
        g.DrawImage(img, 10, 10)
        MyBase.OnPaint(e)
    End Sub
    Private Sub LockBitsTest(ByVal img As Bitmap)
        Dim b_data As Drawing.Imaging.BitmapData = img.LockBits(New Rectangle(0, 0, img.Width, img.Height), Imaging.ImageLockMode.ReadWrite, Imaging.PixelFormat.Format32bppArgb)
        Dim ptr As IntPtr = b_data.Scan0
        Dim bytes As Integer = b_data.Stride * b_data.Height
        Dim img_bytes(bytes - 1) As Byte
        System.Runtime.InteropServices.Marshal.Copy(ptr, img_bytes, 0, bytes)
        Dim y, x As Integer
        For y = 1 To img.Height - 2
            For x = 1 To img.Width - 2
                Try
                    img_bytes((y * img.Width + x) * 4) = 255
                    img_bytes((y * img.Width + x) * 4 + 1) = 255
                    'img_bytes((y * img.Width + x) * 4 + 2) = n_px.G
                    'img_bytes((y * img.Width + x) * 4 + 3) = n_px.B
                Catch ex As Exception
                    GoTo finish_sub
                End Try
            Next
        Next
finish_sub:
        img.UnlockBits(b_data)
    End Sub
End Class

It gave me no errors, but the image didn't change.

What's wrong?

Pretty in depth example here. Blurring should be in the convolution filters section.

Image Processing / Lockbits

Ok, so Int32s instead. I'll try it. Thanks!