How Can I Check for Blurry Image using Imagemagick.Net

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I am work on an ASP.NetCore 5 project that requires users to upload document using a normal file picker, so i have to check if the document the user is uploading is blurry before resampling it and saving it to a database.

I did some research and found out that imagemagick.net would help me accomplish all of that, but can't seem to find a way around it

asp.net-core-5.0 asp.net-core asp.net-mvc asp.net c#
1 Answers

I just googled a bit around and fiddled some Stackoverflow / Blog answers to this together:

public static class ImageExtensions
{
  // as seen here: https://pyimagesearch.com/2015/09/07/blur-detection-with-opencv/
  public static bool IsBlurry(this Image image, double threshold = 100.0)
  {
    var mat = GetMatFromSDImage(image);
    var varianceOfLaplacian = VarianceOfLaplacian(mat);
    return varianceOfLaplacian < threshold;
  }


  // as seen here: https://stackoverflow.com/questions/58005091/how-to-get-the-variance-of-laplacian-in-c-sharp
  private static double VarianceOfLaplacian(Mat mat)
  {
    using var laplacian = new Mat();
    CvInvoke.Laplacian(mat, laplacian, DepthType.Cv64F);
    var mean = new MCvScalar();
    var stddev = new MCvScalar();
    CvInvoke.MeanStdDev(laplacian, ref mean, ref stddev);
    return stddev.V0 * stddev.V0;
  }

  // as found here https://stackoverflow.com/questions/40384487/system-drawing-image-to-emgu-cv-mat
  private static Mat GetMatFromSDImage(Image image)
  {
    int stride = 0;
    Bitmap bmp = new Bitmap(image);

    System.Drawing.Rectangle rect = new System.Drawing.Rectangle(0, 0, bmp.Width, bmp.Height);
    System.Drawing.Imaging.BitmapData bmpData = bmp.LockBits(rect, System.Drawing.Imaging.ImageLockMode.ReadWrite, bmp.PixelFormat);

    System.Drawing.Imaging.PixelFormat pf = bmp.PixelFormat;
    if (pf == System.Drawing.Imaging.PixelFormat.Format32bppArgb)
    {
      stride = bmp.Width * 4;
    }
    else
    {
      stride = bmp.Width * 3;
    }

    Image<Bgra, byte> cvImage = new Image<Bgra, byte>(bmp.Width, bmp.Height, stride, (IntPtr)bmpData.Scan0);

    bmp.UnlockBits(bmpData);

    return cvImage.Mat;
  }
}

I noted the origin of the snippets, as nothing has been implemented by me here ;) It does require the Emgu.CV package not imagemagick.

I hope this helps, it passed the few tests, i just did.

user_78566460
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