/// <summary>
/// Filters unwanted contours by checking their width and height based on defined min/max values.
/// </summary>
/// <param name="contours"></param>
/// <param name="min"></param>
/// <param name="max"></param>
/// <returns>Filtered list of contours and their bounding boxes</returns>
public (IList <MatOfPoint>, List <Rect>) FilterContoursBySize(IList <MatOfPoint> contours, int min, int max)
{
IList <MatOfPoint> filteredContours = new JavaList <MatOfPoint>();
List <Rect> boundingBoxes = new List <Rect>();
foreach (MatOfPoint contour in contours)
{
Rect bounds = Imgproc.BoundingRect(contour);
if (bounds.Height > min && bounds.Height < max && bounds.Width > 10 && bounds.Width < bounds.Height)
{
boundingBoxes.Add(bounds);
filteredContours.Add(contour);
}
}
return(filteredContours, boundingBoxes);
}
private bool Detect(Mat bin)
{
// Reset
mRects.Clear();
// Find contours
Mat hierarchy = new Mat();
IList <MatOfPoint> contoursList = new JavaList <MatOfPoint>();
Imgproc.FindContours(bin.Clone(), contoursList, hierarchy, Imgproc.RetrTree, Imgproc.ChainApproxSimple);
// Filter contours
bool detected = false;
for (int iContour = 0; iContour < contoursList.Count(); iContour++)
{
// Areas
Core.Rect rect = Imgproc.BoundingRect(contoursList[iContour]);
double ellipseArea = PI * (rect.Width / 2) * (rect.Height / 2);
double area = Imgproc.ContourArea(contoursList[iContour]);
// Ratios
double boundWidthPerHeight = (double)rect.Width / rect.Height;
double areaPerEllipse = (double)(area) / ellipseArea;
double rectPerFrame = (double)(rect.Area()) / (bin.Size().Width *bin.Size().Height);
// Check constraints
if (rectPerFrame > MIN_SIGN_SIZE_PER_FRAME)
{
if (1 - LIMIT_DIF_SIGN_SIZE < boundWidthPerHeight && boundWidthPerHeight < 1 + LIMIT_DIF_SIGN_SIZE)
{
if (1 - LIMIT_DIF_SIGN_AREA < areaPerEllipse && areaPerEllipse < 1 + LIMIT_DIF_SIGN_AREA)
{
mRects.Add(rect);
detected = true;
}
}
}
}
return(detected);
}
public static async Task <string> detectAndExtractText(Bitmap img)
{
//Matrix für die Bilder
Mat large = new Mat();
Mat small = new Mat();
Mat rgb = new Mat();
//Bild zu Matrix umwandeln
Utils.BitmapToMat(img, large);
// downsample and use it for processing
Imgproc.PyrDown(large, rgb);
//Grey
Imgproc.CvtColor(rgb, small, Imgproc.ColorBgr2gray);
//Gradiant
Mat grad = new Mat();
Size morphsize = new Size(3.0, 3.0);
Mat morphKernel = Imgproc.GetStructuringElement(Imgproc.MorphEllipse, morphsize);
Imgproc.MorphologyEx(small, grad, Imgproc.MorphGradient, morphKernel);
//Binarize
Mat bw = new Mat();
Imgproc.Threshold(grad, bw, 0.0, 255.0, Imgproc.ThreshBinary | Imgproc.ThreshOtsu);
// connect horizontally oriented regions
Mat connected = new Mat();
Size connectsize = new Size(9.0, 1.0);
morphKernel = Imgproc.GetStructuringElement(Imgproc.MorphRect, connectsize);
Imgproc.MorphologyEx(bw, connected, Imgproc.MorphClose, morphKernel);
// find contours
Mat mask = Mat.Zeros(bw.Size(), CvType.Cv8uc1);
JavaList <MatOfPoint> contours = new JavaList <MatOfPoint>();
Mat hierarchy = new Mat();
OpenCV.Core.Point contourPoint = new OpenCV.Core.Point(0, 0);
Imgproc.FindContours(connected, contours, hierarchy, Imgproc.RetrCcomp, Imgproc.ChainApproxSimple, contourPoint);
Scalar zero = new Scalar(0, 0, 0);
Scalar contourscal = new Scalar(255, 255, 255);
Scalar rectScalar = new Scalar(0, 255, 0);
OpenCV.Core.Rect rect;
Mat maskROI;
double r;
double[] contourInfo;
string resulttext = "";
string part;
Bitmap bmpOcr;
Mat croppedPart;
for (int i = 0; i >= 0;)
{
rect = Imgproc.BoundingRect(contours[i]);
maskROI = new Mat(mask, rect);
maskROI.SetTo(zero);
//fill the contour
Imgproc.DrawContours(mask, contours, i, contourscal, Core.Filled);
// ratio of non-zero pixels in the filled region
r = (double)Core.CountNonZero(maskROI) / (rect.Width * rect.Height);
/* assume at least 45% of the area is filled if it contains text */
/* constraints on region size */
/* these two conditions alone are not very robust. better to use something
* like the number of significant peaks in a horizontal projection as a third condition */
if (r > .45 && (rect.Height > 8 && rect.Width > 8))
{
//Imgproc.Rectangle(rgb, rect.Br(), rect.Tl(), rectScalar, 2);
try
{
croppedPart = rgb.Submat(rect);
bmpOcr = Bitmap.CreateBitmap(croppedPart.Width(), croppedPart.Height(), Bitmap.Config.Argb8888);
Utils.MatToBitmap(croppedPart, bmpOcr);
part = await OCR.getText(bmpOcr);
resulttext = resulttext + part;
Console.WriteLine("------------------Durchlauf-------------");
}
catch (Exception e)
{
Android.Util.Log.Debug("Fehler", "cropped part data error " + e.Message);
}
}
//Nächste Element bestimmen
contourInfo = hierarchy.Get(0, i);
i = (int)contourInfo[0];
}
return(resulttext);
}