https://localhost:5001/swagger/LibraryOpenAPISpecification/swagger.json

// load the image and convert it to grayscale
var image = new Mat(fileName);
 
if (rotation != 0)
{
    rotateImage(image, image, rotation, 1);
}
 
if (debug)
{
    Cv2.ImShow("Source", image);
    Cv2.WaitKey(1); // do events
}
 
var gray = new Mat();
var channels = image.Channels();
if (channels > 1)
{
    Cv2.CvtColor(image, gray, ColorConversion.BgrToGray);
}
else
{
    image.CopyTo(gray);
}

// compute the Scharr gradient magnitude representation of the images
// in both the x and y direction
var gradX = new Mat();
Cv2.Sobel(gray, gradX, MatType.CV_32F, xorder: 1, yorder: 0, ksize: -1);
//Cv2.Scharr(gray, gradX, MatType.CV_32F, xorder: 1, yorder: 0);
 
var gradY = new Mat();
Cv2.Sobel(gray, gradY, MatType.CV_32F, xorder: 0, yorder: 1, ksize: -1);
//Cv2.Scharr(gray, gradY, MatType.CV_32F, xorder: 0, yorder: 1);
 
// subtract the y-gradient from the x-gradient
var gradient = new Mat();
Cv2.Subtract(gradX, gradY, gradient);
Cv2.ConvertScaleAbs(gradient, gradient);
 
if (debug)
{
    Cv2.ImShow("Gradient", gradient);
    Cv2.WaitKey(1); // do events
}

// blur and threshold the image
var blurred = new Mat();
Cv2.Blur(gradient, blurred, new Size(9, 9));
 
var threshImage = new Mat();
Cv2.Threshold(blurred, threshImage, thresh, 255, ThresholdType.Binary);
 
if (debug)
{
    Cv2.ImShow("Thresh", threshImage);
    Cv2.WaitKey(1); // do events
}
 
 
// construct a closing kernel and apply it to the thresholded image
var kernel = Cv2.GetStructuringElement(StructuringElementShape.Rect, new Size(21, 7));
var closed = new Mat();
Cv2.MorphologyEx(threshImage, closed, MorphologyOperation.Close, kernel);
 
if (debug)
{
    Cv2.ImShow("Closed", closed);
    Cv2.WaitKey(1); // do events
}
 
 
// perform a series of erosions and dilations
Cv2.Erode(closed, closed, null, iterations: 4);
Cv2.Dilate(closed, closed, null, iterations: 4);
 
if (debug)
{
    Cv2.ImShow("Erode & Dilate", closed);
    Cv2.WaitKey(1); // do events
}

//find the contours in the thresholded image, then sort the contours
//by their area, keeping only the largest one
 
Point[][] contours;
HiearchyIndex[] hierarchyIndexes;
Cv2.FindContours(
    closed,
    out contours,
    out hierarchyIndexes,
    mode: ContourRetrieval.CComp,
    method: ContourChain.ApproxSimple);
 
if (contours.Length == 0)
{
    throw new NotSupportedException("Couldn't find any object in the image.");
}
 
var contourIndex = 0;
var previousArea = 0;
var biggestContourRect = Cv2.BoundingRect(contours[0]);
while ((contourIndex >= 0))
{
    var contour = contours[contourIndex];
 
    var boundingRect = Cv2.BoundingRect(contour); //Find bounding rect for each contour
    var boundingRectArea = boundingRect.Width * boundingRect.Height;
    if (boundingRectArea > previousArea)
    {
        biggestContourRect = boundingRect;
        previousArea = boundingRectArea;
    }
 
    contourIndex = hierarchyIndexes[contourIndex].Next;
}
 
 
var barcode = new Mat(image, biggestContourRect); //Crop the image
Cv2.CvtColor(barcode, barcode, ColorConversion.BgrToGray);
 
Cv2.ImShow("Barcode", barcode);
Cv2.WaitKey(1); // do events

 PM> Install-Package ZXing.Net

private static string getBarcodeText(Mat barcode)
{
    // `ZXing.Net` needs a white space around the barcode
    var barcodeWithWhiteSpace = new Mat(new Size(barcode.Width + 30, barcode.Height + 30), MatType.CV_8U, Scalar.White);
    var drawingRect = new Rect(new Point(15, 15), new Size(barcode.Width, barcode.Height));
    var roi = barcodeWithWhiteSpace[drawingRect];
    barcode.CopyTo(roi);
 
    Cv2.ImShow("Enhanced Barcode", barcodeWithWhiteSpace);
    Cv2.WaitKey(1); // do events
 
    return decodeBarcodeText(barcodeWithWhiteSpace.ToBitmap());
}
 
private static string decodeBarcodeText(System.Drawing.Bitmap barcodeBitmap)
{
    var source = new BitmapLuminanceSource(barcodeBitmap);
 
    // using http://zxingnet.codeplex.com/
    // PM> Install-Package ZXing.Net
    var reader = new BarcodeReader(null, null, ls => new GlobalHistogramBinarizer(ls))
    {
        AutoRotate = true,
        TryInverted = true,
        Options = new DecodingOptions
        {
            TryHarder = true,
            //PureBarcode = true,
            /*PossibleFormats = new List<BarcodeFormat>
                    {
                        BarcodeFormat.CODE_128
                        //BarcodeFormat.EAN_8,
                        //BarcodeFormat.CODE_39,
                        //BarcodeFormat.UPC_A
                    }*/
        }
    };
 
    //var newhint = new KeyValuePair<DecodeHintType, object>(DecodeHintType.ALLOWED_EAN_EXTENSIONS, new Object());
    //reader.Options.Hints.Add(newhint);
 
    var result = reader.Decode(source);
    if (result == null)
    {
        Console.WriteLine("Decode failed.");
        return string.Empty;
    }
 
    Console.WriteLine("BarcodeFormat: {0}", result.BarcodeFormat);
    Console.WriteLine("Result: {0}", result.Text);
 
 
    var writer = new BarcodeWriter
    {
        Format = result.BarcodeFormat,
        Options = { Width = 200, Height = 50, Margin = 4},
        Renderer = new ZXing.Rendering.BitmapRenderer()
    };
    var barcodeImage = writer.Write(result.Text);
    Cv2.ImShow("BarcodeWriter", barcodeImage.ToMat());
 
    return result.Text;
}

var barcodeClone = barcode.Clone();
var barcodeText = getBarcodeText(barcodeClone);
 
if (string.IsNullOrWhiteSpace(barcodeText))
{
    Console.WriteLine("Enhancing the barcode...");
    //Cv2.AdaptiveThreshold(barcode, barcode, 255,
        //AdaptiveThresholdType.GaussianC, ThresholdType.Binary, 9, 1);
    //var th = 119;
    var th = 100;
    Cv2.Threshold(barcode, barcode, th, 255, ThresholdType.ToZero);
    Cv2.Threshold(barcode, barcode, th, 255, ThresholdType.Binary);
    barcodeText = getBarcodeText(barcode);
}
 
Cv2.Rectangle(image,
    new Point(biggestContourRect.X, biggestContourRect.Y),
    new Point(biggestContourRect.X + biggestContourRect.Width, biggestContourRect.Y + biggestContourRect.Height),
    new Scalar(0, 255, 0),
    2);
 
if (debug)
{
    Cv2.ImShow("Segmented Source", image);
    Cv2.WaitKey(1); // do events
}
 
Cv2.WaitKey(0);
Cv2.DestroyAllWindows();