Public Class MeanShift
     Const HISTOGRAM_LENGTH As Integer = 6000
     Private imgWidth As Integer
     Private imgHeight As Integer
     Private trackWinWidth As Integer
     Private trackWinHeight As Integer
     Private currentX As Integer
     Private currentY As Integer
     Private currentHistogram(HISTOGRAM_LENGTH) As Double
     Private tempHistogram(HISTOGRAM_LENGTH) As Double
     ' ---------------------------------------------------
     Public Sub InitMeanShiftTracker(ByVal firstFrame() As Byte, ByVal frameWidth As Integer, ByVal frameHeight As Integer, _
                 ByVal targetPosX As Integer, ByVal targetPosY As Integer, ByVal targetWidth As Integer, ByVal targetHeight As Integer)
         imgWidth = frameWidth
         imgHeight = frameHeight
         currentX = targetPosX
         currentY = targetPosY
         trackWinHeight = targetHeight
         trackWinWidth = targetWidth
     End Sub
     Public Function CalcHistogramSp(ByVal frame() As Byte, ByVal histogram() As Double) As Integer
         Dim pxValue As Integer = 0
         For i As Integer = 0 To HISTOGRAM_LENGTH
             histogram(i) = 0
         Next
         For j As Long = Math.Max(0, currentY - trackWinHeight / 2) To Math.Min(currentY + trackWinHeight / 2, imgHeight - 1)
             For i As Integer = Math.Max(0, currentX - trackWinWidth / 2) To Math.Min(currentX + trackWinWidth / 2, imgWidth - 1)
                 Dim r As Integer = frame(j * imgWidth * 3 + i * 3) / 16
                 Dim g As Integer = frame(j * imgWidth * 3 + i * 3 + 1) / 16
                 Dim b As Integer = frame(j * imgWidth * 3 + i * 3 + 2) / 16
                 histogram(Int(256 * r + 16 * g + b)) += 1
                 pxValue += 1


             Next
         Next
         For i As Integer = 0 To HISTOGRAM_LENGTH
             histogram(i) /= pxValue
         Next
         Return pxValue
     End Function
     Public Function MeanShiftProcessSp(ByVal frame() As Byte)
         Dim weights(HISTOGRAM_LENGTH) As Double
         Dim newX As Double = 0.0
         Dim newY As Double = 0.0
         For i As Integer = 0 To HISTOGRAM_LENGTH
             If currentHistogram(i) > 0.0 Then
                 weights(i) = tempHistogram(i) / currentHistogram(i)
             Else
                 weights(i) = 0
             End If
         Next
         Dim sumOfWeights As Double = 0.0
         For j As Long = Math.Max(0, currentY - trackWinHeight / 2) To Math.Min(currentY + trackWinHeight / 2, imgHeight - 1)
             For i As Integer = Math.Max(0, currentX - trackWinWidth / 2) To Math.Min(currentX + trackWinWidth / 2, imgWidth - 1)
                 Dim r As Integer = frame(j * imgWidth * 3 + i * 3) / 16
                 Dim g As Integer = frame(j * imgWidth * 3 + i * 3 + 1) / 16
                 Dim b As Integer = frame(j * imgWidth * 3 + i * 3 + 2) / 16
                 Dim ptr As Integer = 256 * r + 16 * g + b
                 newX += weights(ptr) * i
                 newY += weights(ptr) * j
                 sumOfWeights += weights(ptr)
             Next


         Next
         If sumOfWeights <> 0 Then
             currentX = Int(newX / sumOfWeights) + 0.5
             currentY = Int(newY / sumOfWeights) + 0.5
         End If
         Return Nothing
     End Function
     Public Function MeanShiftTrackProcess(ByVal frame() As Byte, ByVal frameNumber As Integer)
         If frameNumber = 0 Then
             Me.CalcHistogramSp(frame, tempHistogram)
         Else
             Dim stopThreshold As Integer = 10
             Dim counter As Integer = 0
             While counter < stopThreshold
                 Me.CalcHistogramSp(frame, currentHistogram)
                 Me.MeanShiftProcessSp(frame)
                 counter += 1
             End While
             Me.DrawTrackBox(frame)
         End If
         Return Nothing
     End Function
     Public Sub DrawTrackBox(ByVal frame() As Byte)
         For i As Integer = currentX To Math.Min(imgWidth, currentX + trackWinWidth)
             frame(currentY * imgWidth * 3 + i * 3 + 0) = 0
             frame(currentY * imgWidth * 3 + i * 3 + 1) = 0
             frame(currentY * imgWidth * 3 + i * 3 + 2) = 255
             frame(Math.Min(imgHeight - 1, currentY + trackWinHeight) * imgWidth * 3 + i * 3 + 0) = 0
             frame(Math.Min(imgHeight - 1, currentY + trackWinHeight) * imgWidth * 3 + i * 3 + 1) = 0
             frame(Math.Min(imgHeight - 1, currentY + trackWinHeight) * imgWidth * 3 + i * 3 + 2) = 255
         Next
         For j As Integer = currentY To Math.Min(imgHeight - 1, currentY + trackWinHeight)
             frame(j * imgWidth * 3 + currentX * 3 + 0) = 0
             frame(j * imgWidth * 3 + currentX * 3 + 1) = 0
             frame(j * imgWidth * 3 + currentX * 3 + 2) = 255
             frame(j * imgWidth * 3 + Math.Min(imgWidth - 1, currentX + trackWinWidth) * 3 + 0) = 0
             frame(j * imgWidth * 3 + Math.Min(imgWidth - 1, currentX + trackWinWidth) * 3 + 1) = 0
             frame(j * imgWidth * 3 + Math.Min(imgWidth - 1, currentX + trackWinWidth) * 3 + 2) = 255
         Next
     End Sub
End Class

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