// NOTE : Also seems not well written and craves optimization at places. P.A.N.A.R.G.O. // => frame = 8 bit greyscale CvMat static public void ContrastEnhancement(CvMat frame) { //CvMat originalFrame = frame; // return this if cannot enhance //if (frame.ElemType != MatrixType.U8C1) // frame = MatOps.Convert(frame, MatrixType.U8C1, 1 / 255.0 ); /////original histogram const int HistBinSize = 256; int[] histSizes = new int[1]; histSizes[0] = HistBinSize; CvHistogram hist = new CvHistogram(histSizes, HistogramFormat.Array); Cv.CalcArrHist(frame, hist, false); // size = 256 implied CvHistogram newHist = MatOps.CopyHistogram(hist); CvArr newHistBin = newHist.Bins; //double[] origVals = new double[hist.Bins.GetDims( 0 )]; List <double> origVals = new List <double>(HistBinSize); for (int i = 0; i < HistBinSize; i++) { double elem = newHistBin.GetReal1D(i); if (elem != 0) { origVals.Add(elem); } } // FIX : See no need for histL, since we have origVals //////histogram with only nonzero bins //CvMat histL = new CvMat( imageRows, imageCols, MatrixType.F32C1, new CvScalar( 0 ) ); //for (i = 0; i < origVals.size(); i++) // histL.at<float>( i, 0 ) = origVals.at( i ); List <double> peakValues = new List <double>(HistBinSize); //std::vector<int> peakValues; //////////3 bin search window for (int i = 1; i < origVals.Count - 2; ++i) { double elem = origVals[i]; if (elem > origVals[i - 1] && elem > origVals[i + 1]) { peakValues.Add(elem); } } if (peakValues.Count == 0) { //Console.Out.WriteLine( "Cannot enhance" ); return; // cannot enhance? } //////Upper threshold double threshUP = 0; for (int i = 0; i < peakValues.Count; ++i) { threshUP += peakValues[i]; } threshUP /= peakValues.Count; //////Lower threshold double threshDOWN = Math.Min((frame.Cols * frame.Rows), threshUP * origVals.Count) / 256.0; //Console.Out.WriteLine( "Enhance thresholds " + threshUP + "/" + threshDOWN ); //////histogram reconstruction CvArr histBins = hist.Bins; for (int i = 0; i < HistBinSize; ++i) { double histElem = histBins.GetReal1D(i); if (histElem > threshUP) { histBins.SetReal1D(i, threshUP); } else if (histElem <= threshUP && histElem >= threshDOWN) { continue; } else if (histElem < threshDOWN && histElem > 0) { histBins.SetReal1D(i, threshDOWN); } else if (histElem == 0) { continue; } } // accumulated values(?) double[] accVals = new double[HistBinSize]; //std::vector<int> accVals; accVals[0] = (histBins.GetReal1D(0)); for (int i = 1; i < HistBinSize; ++i) { accVals[i] = (accVals[i - 1] + histBins[i]); } byte[] lookUpTable = new byte[HistBinSize]; //cv::Mat lookUpTable = cv::Mat::zeros( hist.size(), CV_8UC1 ); for (int i = 0; i < HistBinSize; ++i) { lookUpTable[i] = (byte)(255.0 * accVals[i] / accVals[255]); } // assign computed values to input frame //Console.Out.Write( "Enhance-->" ); for (int i = 0; i < frame.Cols; ++i) { for (int j = 0; j < frame.Rows; ++j) { // there is NO mask, thus no need to check for; was: "if (mask.data)..." byte oldValue = (byte)frame.Get2D(j, i); byte newValue = lookUpTable[oldValue]; //if ((newValue <1 || newValue > 254) && (newValue != oldValue)) Console.Out.Write( oldValue + " " + newValue + "|"); frame.Set2D(j, i, newValue); //frame.SetReal2D( j, i, lookUpTable[ (int)(255.0 * frame.GetReal2D( j, i )) ] / 255.0); } } //Console.Out.WriteLine(); //frame = MatOps.Convert( frame, MatrixType.U8C1, 255.0 ); }