How to detect blur image

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C#

as far i explore i am able to find how to blur an image.
not able to find how to detect blur image.

my requirement is when scanning some images got blurred due to scanning problem.
i have to find that image.

What I have tried:

i have tried with these tools opencv,clearimage,imagemagik,emgu.cv but not able to find the correct way.

private static void GetBlur(string imgfile)
        {
            using (var img = new Image<Gray, byte>(imgfile))
            {
                using (var gray_image = img.Convert<Gray, short>())
                {
                    short maxLap = -32767;
                    foreach (var myByte in gray_image.Data)
                    {
                        if (myByte > maxLap)
                            maxLap = myByte;
                    }
                }
            }
        }

        private static void Blur(Bitmap image)
        {
            Image<Gray, byte> My_Image = new Image<Gray, byte>(image);
            Image<Gray, double> gray_image = My_Image.Convert<Gray, double>();
            //Gray Image
            var my_intensity = gray_image.Data[0, 0, 0];
        }

please suggest me a right way to do.