Detect blur image

edit

Thanks you very much for your answers : I finaly use Laplacian/gauss filter and get stronger pixel to estimate blur : it's Ok for my need. I translate C++ code to VB.Net and use EMGU Opencv library. this is my code :

Module Module1
Private Sub GetBlur(ByVal imgfile As String)
    Dim factor As Single
    Dim imgB As Bitmap = New Bitmap(imgfile)
    imgB = New Bitmap(imgB)
    Dim imgGray As Image(Of Gray, Byte) = img.Convert(Of Gray, Byte)()
    Dim imgTmp As Image(Of Gray, Single) = imgGray.Laplace(1)
    Dim maxLap As Short = -32767
    For Each MyByte As Single In imgTmp.Data
        If MyByte > maxLap Then
            maxLap = MyByte
        End If
    Next
    Debug.Print(imgfile & "   " & maxLap)
    imgGray.Dispose()
    img.Dispose()
    imgTmp.Dispose()
    imgB.Dispose()
End Sub

End Module

Where Maxlap is the "blur score" of the picture.

Alan