private static Bitmap ProcessImage(Bitmap image, byte blueThreshold = 139) { try { var imageClone = image.Clone(new Rectangle(0, 0, image.Width, image.Height), image.PixelFormat); var info = new CaptchaInfo(); imageClone = imageClone.AdjustCurves2() .GetCaptchaInfo(ref info); imageClone = image.AdjustCurves2() .CleanUnecessaryPixel(info) .BlackenColor() .CleanUnecessaryPixel(info) .Sharpen(); return(imageClone); } catch (Exception ex) { Console.WriteLine(ex.Message); } return(null); }