Update OscillationEvent.cs

Issue #469
1: Added the Periodicity Property to the Oscillation Event class.
2: Fixed the Draw() method for Oscillation events. The events were not drawing.
3: Added a method to trim Oscillation events using the decibel values as a guide to where the true bounds should be.

src/AudioAnalysisTools/Events/Types/OscillationEvent.cs

@@ -7,27 +7,90 @@ namespace AudioAnalysisTools
     using System;
     using AudioAnalysisTools.Events;
     using AudioAnalysisTools.Events.Drawing;
+    using AudioAnalysisTools.StandardSpectrograms;
+    using SixLabors.ImageSharp;
     using SixLabors.ImageSharp.Processing;
+    using TowseyLibrary;
 
     public class OscillationEvent : SpectralEvent
     {
         public OscillationEvent()
         {
         }
 
+        /// <summary>
+        /// Gets or sets the period in seconds between consecutive oscillations.
+        /// </summary>
+        public double Periodicity { get; set; }
+
         // TODO: add extra metadata!!!
 
+        /// <summary>
+        /// Draws a border around this oscillation event.
+        /// </summary>
         public override void Draw(IImageProcessingContext graphics, EventRenderingOptions options)
         {
-            // foreach (var track in tracks) {
-            // track.Draw(...)
-            // }
+            if (options.DrawBorder)
+            {
+                var border = options.Converters.GetPixelRectangle(this);
+                graphics.NoAA().DrawBorderInset(options.Border, border);
+            }
+
+            this.DrawScoreIndicator(graphics, options);
+            this.DrawEventLabel(graphics, options);
+        }
+
+        /// <summary>
+        /// Extracts an event from a spectrogram given its bounds.
+        /// Then trims the event because oscillation events do not typically start where the DCT places them.
+        /// </summary>
+        public static (int EventStart, int EventEnd, double FramePeriod) TrimEvent(SpectrogramStandard spectrogram, int startFrame, int minBin, int endFrame, int maxBin)
+        {
+            //obtain the oscillation event's periodicity.
+            //extract the relevant portion of the spectrogram.
+            var eventMatrix = MatrixTools.Submatrix<double>(spectrogram.Data, startFrame, minBin, endFrame, maxBin);
+            var frameAverages = MatrixTools.GetRowAverages(eventMatrix);
+            frameAverages = DataTools.normalise(frameAverages);
+            double threshold = 0.25;
+
+            // find the true start frame
+            int startFrameOffset = 0;
+            for (int frame = 1; frame < frameAverages.Length; frame++)
+            {
+                startFrameOffset++;
+                if (frameAverages[frame - 1] < threshold && frameAverages[frame] >= threshold)
+                {
+                    break;
+                }
+            }
+
+            int endFrameOffset = 0;
+            for (int frame = frameAverages.Length - 1; frame >= 0; frame--)
+            {
+                endFrameOffset++;
+                if (frameAverages[frame - 1] >= threshold && frameAverages[frame] < threshold)
+                {
+                    break;
+                }
+            }
+
+            int trueStartFrame = startFrame + startFrameOffset;
+            int trueEndFrame = endFrame - endFrameOffset;
+            int trueFrameLength = trueEndFrame - trueStartFrame + 1;
+
+            // determine the number of times the frame values step from below to above average.
+            int stepCount = 0;
+            for (int frame = 1; frame < frameAverages.Length; frame++)
+            {
+                if (frameAverages[frame - 1] < threshold && frameAverages[frame] >= threshold)
+                {
+                    stepCount++;
+                }
+            }
 
-            //this.Track.Draw(graphics, options);
+            double framePeriod = trueFrameLength / (double)stepCount;
 
-            //  base drawing (border)
-            // TODO: unless border is disabled
-            base.Draw(graphics, options);
+            return (trueStartFrame, trueEndFrame, framePeriod);
         }
     }
 }