add xml dev notes

gr/Microsoft.VisualBasic.Imaging/Drawing2D/HeatMap/HeatMapRaster.vb

@@ -57,6 +57,7 @@
 #End Region
 
 Imports System.Drawing
+Imports System.Runtime.CompilerServices
 Imports Microsoft.VisualBasic.Imaging.Math2D
 Imports std = System.Math
 
@@ -139,12 +140,13 @@ Namespace Drawing2D.HeatMap
 
         Private Sub gaussiankernel()
             Dim y = -r, i = 0
+            Dim sigma_2 As Double = gSigma ^ 2
 
             While i < gSize
                 Dim x = -r, j = 0
 
                 While j < gSize
-                    m_kernelField(i, j) = std.Exp((x * x + y * y) / (-2 * gSigma * gSigma)) / (2 * std.PI * gSigma * gSigma)
+                    m_kernelField(i, j) = std.Exp((x * x + y * y) / (-2 * sigma_2)) / (2 * std.PI * sigma_2)
                     x += 1
                     j += 1
                 End While
@@ -156,14 +158,15 @@ Namespace Drawing2D.HeatMap
 
         Private Function MultiplyKernel(weight As Double) As Double(,)
             Dim wKernel As Double(,) = CType(m_kernelField.Clone(), Double(,))
-            For i = 0 To gSize - 1
-                For j = 0 To gSize - 1
+            For i As Integer = 0 To gSize - 1
+                For j As Integer = 0 To gSize - 1
                     wKernel(i, j) *= weight
                 Next
             Next
             Return wKernel
         End Function
 
+        <MethodImpl(MethodImplOptions.AggressiveInlining)>
         Public Function SetDatas(datas As IEnumerable(Of T)) As HeatMapRaster(Of T)
             Return SetDataInternal(datas.ToArray)
         End Function
@@ -221,6 +224,15 @@ Namespace Drawing2D.HeatMap
             Return Me
         End Function
 
+        ''' <summary>
+        ''' cast the sparse raster data as dense matrx liked raster data
+        ''' </summary>
+        ''' <param name="datas"></param>
+        ''' <param name="w">the matrix width, ncols</param>
+        ''' <param name="h">the matrix height, nrows</param>
+        ''' <returns>the full scan <see cref="PixelData"/> spot data, number of 
+        ''' the returns collection equals to <paramref name="w"/> * <paramref name="h"/>.
+        ''' </returns>
         Public Shared Iterator Function PopulateDenseRasterMatrix(datas As IEnumerable(Of T), w As Integer, h As Integer) As IEnumerable(Of Pixel)
             Dim matrix = datas _
                 .GroupBy(Function(a) a.X) _
@@ -254,6 +266,13 @@ Namespace Drawing2D.HeatMap
             Next
         End Function
 
+        ''' <summary>
+        ''' 
+        ''' </summary>
+        ''' <param name="activator">
+        ''' a delegate function for create the pixel spot data object
+        ''' </param>
+        ''' <returns></returns>
         Public Iterator Function GetRasterPixels(activator As Func(Of Integer, Integer, Double, T)) As IEnumerable(Of T)
             For i = 0 To m_heatMatrix.GetLength(0) - 1
                 For j = 0 To m_heatMatrix.GetLength(1) - 1
@@ -262,6 +281,10 @@ Namespace Drawing2D.HeatMap
             Next
         End Function
 
+        ''' <summary>
+        ''' populate out the default internal <see cref="PixelData"/> model
+        ''' </summary>
+        ''' <returns></returns>
         Public Iterator Function GetRasterPixels() As IEnumerable(Of Pixel) Implements IRasterGrayscaleHeatmap.GetRasterPixels
             For i = 0 To m_heatMatrix.GetLength(0) - 1
                 For j = 0 To m_heatMatrix.GetLength(1) - 1