/// <summary> /// Draw the model image and observed image, the matched features and homography projection. /// Based on EMGU's SURF example. /// </summary> /// <param name="modelImage">The model image</param> /// <param name="observedImage">The observed image</param> /// <param name="matchTime">The output total time for computing the homography matrix.</param> /// <returns>The model image and observed image, the matched features and homography projection.</returns> private static Image <Bgr, Byte> Draw(Image <Gray, Byte> modelImage, Image <Gray, byte> observedImage, out long matchTime, out PointF[] border, out double confidence) { Stopwatch watch; HomographyMatrix homography = null; SURFDetector surfCPU = new SURFDetector(500, false); VectorOfKeyPoint modelKeyPoints; VectorOfKeyPoint observedKeyPoints; Matrix <int> indices; Matrix <byte> mask; int k = 2; double uniquenessThreshold = 0.8; if (GpuInvoke.HasCuda) { GpuSURFDetector surfGPU = new GpuSURFDetector(surfCPU.SURFParams, 0.01f); using (GpuImage <Gray, Byte> gpuModelImage = new GpuImage <Gray, byte>(modelImage)) //extract features from the object image using (GpuMat <float> gpuModelKeyPoints = surfGPU.DetectKeyPointsRaw(gpuModelImage, null)) using (GpuMat <float> gpuModelDescriptors = surfGPU.ComputeDescriptorsRaw(gpuModelImage, null, gpuModelKeyPoints)) using (GpuBruteForceMatcher <float> matcher = new GpuBruteForceMatcher <float>(DistanceType.L2)) { modelKeyPoints = new VectorOfKeyPoint(); surfGPU.DownloadKeypoints(gpuModelKeyPoints, modelKeyPoints); watch = Stopwatch.StartNew(); // extract features from the observed image using (GpuImage <Gray, Byte> gpuObservedImage = new GpuImage <Gray, byte>(observedImage)) using (GpuMat <float> gpuObservedKeyPoints = surfGPU.DetectKeyPointsRaw(gpuObservedImage, null)) using (GpuMat <float> gpuObservedDescriptors = surfGPU.ComputeDescriptorsRaw(gpuObservedImage, null, gpuObservedKeyPoints)) using (GpuMat <int> gpuMatchIndices = new GpuMat <int>(gpuObservedDescriptors.Size.Height, k, 1, true)) using (GpuMat <float> gpuMatchDist = new GpuMat <float>(gpuObservedDescriptors.Size.Height, k, 1, true)) using (GpuMat <Byte> gpuMask = new GpuMat <byte>(gpuMatchIndices.Size.Height, 1, 1)) using (Stream stream = new Stream()) { matcher.KnnMatchSingle(gpuObservedDescriptors, gpuModelDescriptors, gpuMatchIndices, gpuMatchDist, k, null, stream); indices = new Matrix <int>(gpuMatchIndices.Size); mask = new Matrix <byte>(gpuMask.Size); //gpu implementation of voteForUniquess using (GpuMat <float> col0 = gpuMatchDist.Col(0)) using (GpuMat <float> col1 = gpuMatchDist.Col(1)) { GpuInvoke.Multiply(col1, new MCvScalar(uniquenessThreshold), col1, stream); GpuInvoke.Compare(col0, col1, gpuMask, CMP_TYPE.CV_CMP_LE, stream); } observedKeyPoints = new VectorOfKeyPoint(); surfGPU.DownloadKeypoints(gpuObservedKeyPoints, observedKeyPoints); //wait for the stream to complete its tasks //We can perform some other CPU intesive stuffs here while we are waiting for the stream to complete. stream.WaitForCompletion(); gpuMask.Download(mask); gpuMatchIndices.Download(indices); if (GpuInvoke.CountNonZero(gpuMask) >= 4) { int nonZeroCount = Features2DToolbox.VoteForSizeAndOrientation(modelKeyPoints, observedKeyPoints, indices, mask, 1.5, 20); if (nonZeroCount >= 4) { homography = Features2DToolbox.GetHomographyMatrixFromMatchedFeatures(modelKeyPoints, observedKeyPoints, indices, mask, 2); } } confidence = ComputeScore(gpuMatchDist.ToMatrix(), gpuMask.ToMatrix()); watch.Stop(); } } } else { //extract features from the object image modelKeyPoints = surfCPU.DetectKeyPointsRaw(modelImage, null); Matrix <float> modelDescriptors = surfCPU.ComputeDescriptorsRaw(modelImage, null, modelKeyPoints); watch = Stopwatch.StartNew(); // extract features from the observed image observedKeyPoints = surfCPU.DetectKeyPointsRaw(observedImage, null); Matrix <float> observedDescriptors = surfCPU.ComputeDescriptorsRaw(observedImage, null, observedKeyPoints); BruteForceMatcher <float> matcher = new BruteForceMatcher <float>(DistanceType.L2); matcher.Add(modelDescriptors); indices = new Matrix <int>(observedDescriptors.Rows, k); using (Matrix <float> dist = new Matrix <float>(observedDescriptors.Rows, k)) { matcher.KnnMatch(observedDescriptors, indices, dist, k, null); mask = new Matrix <byte>(dist.Rows, 1); mask.SetValue(255); Features2DToolbox.VoteForUniqueness(dist, uniquenessThreshold, mask); confidence = ComputeScore(dist, mask); } int nonZeroCount = CvInvoke.cvCountNonZero(mask); if (nonZeroCount >= 4) { nonZeroCount = Features2DToolbox.VoteForSizeAndOrientation(modelKeyPoints, observedKeyPoints, indices, mask, 1.5, 20); if (nonZeroCount >= 4) { homography = Features2DToolbox.GetHomographyMatrixFromMatchedFeatures(modelKeyPoints, observedKeyPoints, indices, mask, 2); } } watch.Stop(); } //Draw the matched keypoints Image <Bgr, Byte> result = Features2DToolbox.DrawMatches(modelImage, modelKeyPoints, observedImage, observedKeyPoints, indices, new Bgr(255, 255, 255), new Bgr(255, 255, 255), mask, Features2DToolbox.KeypointDrawType.DEFAULT); #region draw the projected region on the image if (homography != null) { //draw a rectangle along the projected model Rectangle rect = modelImage.ROI; PointF[] pts = new PointF[] { new PointF(rect.Left, rect.Bottom), new PointF(rect.Right, rect.Bottom), new PointF(rect.Right, rect.Top), new PointF(rect.Left, rect.Top) }; homography.ProjectPoints(pts); border = pts; result.DrawPolyline(Array.ConvertAll <PointF, Point>(pts, Point.Round), true, new Bgr(Color.Red), 5); } else { border = null; } #endregion matchTime = watch.ElapsedMilliseconds; return(result); }