Gaussian Blur

This algorithm is the result of blurring an image by a Gaussian function.

   

• C#
• VB.Net

									Private Class ConvolutionMatrix
	Public Sub New()
		Pixel = 1
		Factor = 1
	End Sub

	Public Sub Apply(Val As Integer)
		TopLeft = Val
		TopMid = Val
		TopRight = Val
		MidLeft = Val
		MidRight = Val
		BottomLeft = Val
		BottomMid = Val
		BottomRight = Val
		Pixel = Val
	End Sub

	Public Property TopLeft() As Integer
		Get
			Return m_TopLeft
		End Get
		Set(value As Integer)
			m_TopLeft = value
		End Set
	End Property
	Private m_TopLeft As Integer

	Public Property TopMid() As Integer
		Get
			Return m_TopMid
		End Get
		Set(value As Integer)
			m_TopMid = value
		End Set
	End Property
	Private m_TopMid As Integer

	Public Property TopRight() As Integer
		Get
			Return m_TopRight
		End Get
		Set(value As Integer)
			m_TopRight = value
		End Set
	End Property
	Private m_TopRight As Integer

	Public Property MidLeft() As Integer
		Get
			Return m_MidLeft
		End Get
		Set(value As Integer)
			m_MidLeft = value
		End Set
	End Property
	Private m_MidLeft As Integer

	Public Property MidRight() As Integer
		Get
			Return m_MidRight
		End Get
		Set(value As Integer)
			m_MidRight = value
		End Set
	End Property
	Private m_MidRight As Integer

	Public Property BottomLeft() As Integer
		Get
			Return m_BottomLeft
		End Get
		Set(value As Integer)
			m_BottomLeft = value
		End Set
	End Property
	Private m_BottomLeft As Integer

	Public Property BottomMid() As Integer
		Get
			Return m_BottomMid
		End Get
		Set(value As Integer)
			m_BottomMid = value
		End Set
	End Property
	Private m_BottomMid As Integer

	Public Property BottomRight() As Integer
		Get
			Return m_BottomRight
		End Get
		Set(value As Integer)
			m_BottomRight = value
		End Set
	End Property
	Private m_BottomRight As Integer

	Public Property Pixel() As Integer
		Get
			Return m_Pixel
		End Get
		Set(value As Integer)
			m_Pixel = value
		End Set
	End Property
	Private m_Pixel As Integer

	Public Property Factor() As Integer
		Get
			Return m_Factor
		End Get
		Set(value As Integer)
			m_Factor = value
		End Set
	End Property
	Private m_Factor As Integer

	Public Property Offset() As Integer
		Get
			Return m_Offset
		End Get
		Set(value As Integer)
			m_Offset = value
		End Set
	End Property
	Private m_Offset As Integer
End Class

Private Class Convolution
	Public Sub Convolution3x3(ByRef bmp As Bitmap)
		Dim Factor As Integer = Matrix.Factor

		If Factor = 0 Then
			Return
		End If

		Dim TopLeft As Integer = Matrix.TopLeft
		Dim TopMid As Integer = Matrix.TopMid
		Dim TopRight As Integer = Matrix.TopRight
		Dim MidLeft As Integer = Matrix.MidLeft
		Dim MidRight As Integer = Matrix.MidRight
		Dim BottomLeft As Integer = Matrix.BottomLeft
		Dim BottomMid As Integer = Matrix.BottomMid
		Dim BottomRight As Integer = Matrix.BottomRight
		Dim Pixel As Integer = Matrix.Pixel
		Dim Offset As Integer = Matrix.Offset

		Dim TempBmp As Bitmap = bmp.Clone()

		Dim bmpData As BitmapData = bmp.LockBits(New Rectangle(0, 0, bmp.Width, bmp.Height), ImageLockMode.ReadWrite, PixelFormat.Format24bppRgb)
		Dim TempBmpData As BitmapData = TempBmp.LockBits(New Rectangle(0, 0, TempBmp.Width, TempBmp.Height), ImageLockMode.[ReadOnly], PixelFormat.Format24bppRgb)

		Dim ptr As IntPtr = bmpData.Scan0
		Dim TempPtr As IntPtr = TempBmpData.Scan0

		Dim Pix As Integer = 0
		Dim Stride As Integer = bmpData.Stride
		Dim DoubleStride As Integer = Stride * 2
		Dim Width As Integer = bmp.Width - 2
		Dim Height As Integer = bmp.Height - 2
		Dim stopAddress As Integer = CInt(ptr) + bmpData.Stride * bmpData.Height

		For y As Integer = 0 To Height - 1
			For x As Integer = 0 To Width - 1
				Pix = (((((Marshal.ReadByte(TempPtr + 2) * TopLeft) + (Marshal.ReadByte(TempPtr + 5) * TopMid) + (Marshal.ReadByte(TempPtr + 8) * TopRight)) + _
						 ((Marshal.ReadByte(TempPtr + 2 + Stride) * MidLeft) + (Marshal.ReadByte(TempPtr + 5 + Stride) * Pixel) + (Marshal.ReadByte(TempPtr + 8 + Stride) * MidRight)) + _
						 ((Marshal.ReadByte(TempPtr + 2 + DoubleStride) * BottomLeft) + (Marshal.ReadByte(TempPtr + 5 + DoubleStride) * BottomMid) + (Marshal.ReadByte(TempPtr + 8 + DoubleStride) * BottomRight))) \ Factor) + Offset)

				If Pix < 0 Then
					Pix = 0
				ElseIf Pix > 255 Then
					Pix = 255
				End If

				Marshal.WriteByte(ptr + 5 + Stride, CByte(Pix))

				Pix = (((((Marshal.ReadByte(TempPtr + 1) * TopLeft) + (Marshal.ReadByte(TempPtr + 4) * TopMid) + (Marshal.ReadByte(TempPtr + 7) * TopRight)) + _
						 ((Marshal.ReadByte(TempPtr + 1 + Stride) * MidLeft) + (Marshal.ReadByte(TempPtr + 4 + Stride) * Pixel) + (Marshal.ReadByte(TempPtr + 7 + Stride) * MidRight)) + _
						 ((Marshal.ReadByte(TempPtr + 1 + DoubleStride) * BottomLeft) + (Marshal.ReadByte(TempPtr + 4 + DoubleStride) * BottomMid) + (Marshal.ReadByte(TempPtr + 7 + DoubleStride) * BottomRight))) \ Factor) + Offset)

				If Pix < 0 Then
					Pix = 0
				ElseIf Pix > 255 Then
					Pix = 255
				End If

				Marshal.WriteByte(ptr + 4 + Stride, CByte(Pix))

				Pix = (((((Marshal.ReadByte(TempPtr) * TopLeft) + (Marshal.ReadByte(TempPtr + 3) * TopMid) + (Marshal.ReadByte(TempPtr + 6) * TopRight)) + _
						 ((Marshal.ReadByte(TempPtr + Stride) * MidLeft) + (Marshal.ReadByte(TempPtr + 3 + Stride) * Pixel) + (Marshal.ReadByte(TempPtr + 6 + Stride) * MidRight)) + _
						 ((Marshal.ReadByte(TempPtr + DoubleStride) * BottomLeft) + (Marshal.ReadByte(TempPtr + 3 + DoubleStride) * BottomMid) + (Marshal.ReadByte(TempPtr + 6 + DoubleStride) * BottomRight))) \ Factor) + Offset)

				If Pix < 0 Then
					Pix = 0
				ElseIf Pix > 255 Then
					Pix = 255
				End If

				Marshal.WriteByte(ptr + 3 + Stride, CByte(Pix))

				ptr += 3
				TempPtr += 3
			Next
		Next

		bmp.UnlockBits(bmpData)
		TempBmp.UnlockBits(TempBmpData)
	End Sub

	Public Property Matrix() As ConvolutionMatrix
		Get
			Return m_Matrix
		End Get
		Set(value As ConvolutionMatrix)
			m_Matrix = value
		End Set
	End Property
	Private m_Matrix As ConvolutionMatrix
End Class

Public Shared Sub ApplyGaussianBlur(ByRef bmp As Bitmap, Weight As Integer)
	Dim m As New ConvolutionMatrix()
	m.Apply(1)
	m.Pixel = Weight
	m.TopMid = 2
	m.MidLeft = 2
	m.MidRight = 2
	m.BottomMid = 2
	m.Factor = Weight + 12

	Dim C As New Convolution()
	C.Matrix = m
	C.Convolution3x3(bmp)
End Sub
								

Example

									DIm b As Bitmap = CType(Image.FromFile("rose.jpg"), Bitmap)
ApplyGaussianBlur(b, 4)