vb.net 教程 5-15 图像处理之内存处理6- VB

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具体算法请参看《vb.net 教程 5-13 图像处理之像素处理 6》

黑白：

'黑白1
'http://blog.csdn.net/uruseibest
Private Sub btn2Color1_Click(sender As Object, e As EventArgs) Handles btn2Color1.Click
Dim destImg As New Bitmap(sourceImg.Width, sourceImg.Height)
Dim sourceData As BitmapData = sourceImg.LockBits(New Rectangle(0, 0, sourceImg.Width, sourceImg.Height), ImageLockMode.ReadOnly, PixelFormat.Format24bppRgb)
Dim destData As BitmapData = destImg.LockBits(New Rectangle(0, 0, sourceImg.Width, sourceImg.Height), ImageLockMode.WriteOnly, PixelFormat.Format24bppRgb)

Dim pSource As IntPtr = sourceData.Scan0
Dim allBytes As Integer = sourceData.Stride * sourceData.Height
Dim rgbvalues() As Byte
ReDim rgbvalues(allBytes - 1)
Marshal.Copy(pSource, rgbvalues, 0, allBytes)

Dim pos As Integer = 0
Dim R, G, B As Integer
Dim avgValue As Integer

For j As Integer = 0 To sourceData.Height - 1
For i As Integer = 0 To sourceData.Width - 1
B = rgbvalues(pos)
G = rgbvalues(pos + 1)
R = rgbvalues(pos + 2)
avgValue = (B + G + R) / 3
If avgValue >= 128 Then avgValue = 255 Else avgValue = 0
rgbvalues(pos) = avgValue
rgbvalues(pos + 1) = avgValue
rgbvalues(pos + 2) = avgValue

pos = pos + 3
Next
pos = pos + sourceData.Stride - sourceData.Width * 3
Next

Dim pDest As IntPtr = destData.Scan0
Marshal.Copy(rgbvalues, 0, pDest, allBytes)

sourceImg.UnlockBits(sourceData)
destImg.UnlockBits(destData)

picDest.Image = destImg
End Sub

'黑白2
'http://blog.csdn.net/uruseibest
Private Sub btn2Color2_Click(sender As Object, e As EventArgs) Handles btn2Color2.Click
Dim destImg As New Bitmap(sourceImg.Width, sourceImg.Height)
Dim sourceData As BitmapData = sourceImg.LockBits(New Rectangle(0, 0, sourceImg.Width, sourceImg.Height), ImageLockMode.ReadOnly, PixelFormat.Format24bppRgb)
Dim destData As BitmapData = destImg.LockBits(New Rectangle(0, 0, sourceImg.Width, sourceImg.Height), ImageLockMode.WriteOnly, PixelFormat.Format24bppRgb)

Dim pSource As IntPtr = sourceData.Scan0
Dim allBytes As Integer = sourceData.Stride * sourceData.Height
Dim rgbvalues() As Byte
ReDim rgbvalues(allBytes - 1)
Marshal.Copy(pSource, rgbvalues, 0, allBytes)

Dim pos As Integer = 0
Dim R, G, B As Integer

Dim HistGram(255) As Integer

For j As Integer = 0 To sourceData.Height - 1
For i As Integer = 0 To sourceData.Width - 1
R = rgbvalues(pos + 2)
HistGram(R) += 1
pos = pos + 3
Next
pos = pos + sourceData.Stride - sourceData.Width * 3
Next

Dim threshold As Integer

Dim allSum, allCount As Integer
For k As Integer = 0 To 255
allCount += HistGram(k)
allSum += k * HistGram(k)
Next
threshold = allSum / allCount

pos = 0
For j As Integer = 0 To sourceData.Height - 1
For i As Integer = 0 To sourceData.Width - 1
R = rgbvalues(pos + 2)
If R >= threshold Then R = 255 Else R = 0

rgbvalues(pos) = R
rgbvalues(pos + 1) = R
rgbvalues(pos + 2) = R

pos = pos + 3
Next
pos = pos + sourceData.Stride - sourceData.Width * 3
Next

Dim pDest As IntPtr = destData.Scan0
Marshal.Copy(rgbvalues, 0, pDest, allBytes)

sourceImg.UnlockBits(sourceData)
destImg.UnlockBits(destData)

picDest.Image = destImg
End Sub