Visual Basic与图像处理(三)

8、Priwitt微分算子

Prewitt微分算子的思路与Sobel微分算子的思路类似，也是在一个3×3模板下进行图像的锐化处理。Prewitt微分算子的定义如下：

上面的式子同样也可以用模板进行表示：

Priwitt微分算子与Sobel微分算子的模板基本一样，只是系数的微调，因此处理结果也基本一致，从肉眼很难看出明显的差别，本例的运行界面如下：

Priwitt滤波按钮对应的代码如下：

Private Sub cmdPriwittFilter_Click()

Dim i As Integer, j As Integer

    Dim PixelValue As Long

    Dim r As Integer, g As Integer, b As Integer

    Dim GrayValue As Integer

    

    Dim Temp(2, 2) As Integer

    Dim x As Integer, y As Integer

    Dim Dx As Integer, Dy As Integer

    Dim NGrayValue As Integer

   

     '设置目标图像的高度和宽度

    DestImHeight = SourceImHeight - 2 '边界像素直接不要了

    DestImWidth = SourceImWidth - 2

   

    '设置目标PictureBox的大小

    PicDest.Height = DestImHeight

    PicDest.Width = DestImWidth

   

 

    ReDim dbits(DestImHeight - 1, DestImWidth - 1, 2) As Byte '重新定义目标数组的维数

    dbits = sbits '数组的直接复制，只有数组维数完全一样才可以

   

    '图像的Priwitt滤波

   

   

    For i = 1 To SourceImHeight - 2 '边界像素不处理

        For j = 1 To SourceImWidth - 2

            NGrayValue = 0

            For x = 0 To 2

                For y = 0 To 2

               

                    r = sbits(i + 1 - x, j + 1 - y, 0)

                    g = sbits(i + 1 - x, j + 1 - y, 1)

                    b = sbits(i + 1 - x, j + 1 - y, 2)

              '插入图像处理的过程，对r, g, b进行处理

                    Temp(x, y) = 0.3 * r + 0.59 * g + 0.11 * b

                   

                Next y

            Next x

            Dx = -(Temp(0, 0) + Temp(0, 1) + Temp(0, 2)) + (Temp(2, 0) + Temp(2, 1) + Temp(2, 2))

            Dy = -(Temp(0, 0) + Temp(1, 0) + Temp(2, 0)) + (Temp(0, 2) + Temp(1, 2) + Temp(2, 2))

            NGrayValue = Sqr(Dx ^ 2 + Dy ^ 2)

            If NGrayValue > 255 Then NGrayValue = 255

            dbits(i - 1, j - 1, 0) = NGrayValue

            dbits(i - 1, j - 1, 1) = NGrayValue

            dbits(i - 1, j - 1, 2) = NGrayValue

        Next j

    Next i

   

       

   

    Dim tDBmpInfo As BITMAP

    Dim hDestBmp As Long

       

 

    hDestBmp = PicDest.Image.Handle

 

        '获得位图信息

    Call GetObject(hDestBmp, Len(tDBmpInfo), tDBmpInfo)

    ReDim ImageArray(1 To DestImWidth * 4, 1 To DestImHeight) As Byte

     

   

    For i = 1 To DestImHeight

        For j = 1 To DestImWidth

            ImageArray((j - 1) * 4 + 1, i) = dbits(i - 1, j - 1, 2)

            ImageArray((j - 1) * 4 + 2, i) = dbits(i - 1, j - 1, 1)

            ImageArray((j - 1) * 4 + 3, i) = dbits(i - 1, j - 1, 0)

        Next j

    Next i

   

'获得源图与目标图二进制位

 

Call SetBitmapBits(hDestBmp, tDBmpInfo.bmWidthBytes * tDBmpInfo.bmHeight, ImageArray(1, 1))

 

End Sub

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