VB图像处理之像素的获取和输出

　　要处理一个图像，首先要获得该图像的像素值，而VB本身提供的PICTURE控件虽然可以打开很多类型的图片，但是它提供的那个POINT方法读取像素实在是太慢。而使用GetPixel这个API的速度也快不到哪里去，因为PIONT方法本身就是对于GetPixel的一个包装。

　　在VB中要快速获取一幅在PICTURE中打开的图像比较快速的方法是使用DIB方法，当然还有DDB方法，不过使用DDB方法还需要考虑不同颜色深度的图像的分别处理，在程序的实现上要相对复杂，而使用DIB方法则不必，并且在处理速度上比DDB方法也慢的有限。

　　过程一：获得一个在PICTURE控件中打开的图像的所有像素。

Public Sub DibGet(ByVal IdSource As Long, XBegin As Long, ByVal YBegin As Long, ByVal XEnd As Long, ByVal YEnd As Long)
　Dim iBitmap As Long
　Dim iDC As Long
　Dim I As LongDim
　Dim W As Long
　Dim H As Long

　On Error GoTo ErrLine
　Done = False
　TimeGet = timeGetTime
　InPutWid = XEnd - XBegin
　InPutHei = YEnd - YBegin
　W = InPutWid + 1
　H = InPutHei + 1

　I = (Bits \ 8) - 1
　ReDim ColVal(I, InPutWid, InPutHei)
　With bi24BitInfo.bmiHeader
　　.biBitCount = Bits
　　.biCompression = 0&
　　.biPlanes = 1
　　.biSize = Len(bi24BitInfo.bmiHeader)
　　.biWidth = W
　　.biHeight = H
　End With

　iBitmap = GetCurrentObject(IdSource, 7&)
　GetDIBits IdSource, iBitmap, 0&, H, ColVal(0, 0, 0), bi24BitInfo, 0& DeleteObject iBitmap
　Done = True
　TimeGet = timeGetTime - TimeGetExit Sub
ErrLine:
　MsgBox "错误号：" & Err.Number & "：" & Err.Description
End Sub

　　在这个过程中所用到的只是一些参数的设定和API的调用，不涉及算法。

　　过程二：图像输出的过程：

Public Sub DIBPut(ByVal IdDestination As Long)
　Dim W As Long
　Dim H As Long

　On Error GoTo ErrLine
　Done = False
　TimePut = timeGetTime

　W = OutPutWid + 1
　H = OutPutHei + 1

　With bi24BitInfo.bmiHeader
　　.biWidth = W
　　.biHeight = H
　　LineBytes = ((W * Bits + 31) And &HFFFFFFE0) \ 8
　　.biSizeImage = LineBytes * H
　End With
　SetDIBitsToDevice IdDestination, 0, 0, W, H, 0, 0, 0, H, ColOut(0, 0, 0), bi24BitInfo.bmiHeader, 0

　Done = True
　TimePut = timeGetTime - TimePut
　Exit Sub
ErrLine:
　MsgBox Err.Description
End Sub


]   1 2  
  



　　下面解释一下在过程中到的全局变量和数据结构，以及API的定义。

　　API定义：

　　删除一个DC

Private Declare Function DeleteDC Lib "gdi32" (ByVal hdc As Long) As Long

　　删除一个对象

Private Declare Function DeleteObject Lib "gdi32" (ByVal hObject As Long) As Long

　　选择当前对象

Private Declare Function GetCurrentObject Lib "gdi32" (ByVal hdc As Long, ByVal uObjectType As Long) As Long

　　获取DIB

Private Declare Function GetDIBits Lib "gdi32" (ByVal aHDC As Long, ByVal hBitmap As Long, ByVal nStartScan As Long, ByVal nNumScans As Long, lpBits As Any, lpBI As BitMapInfo, ByVal wUsage As Long) As Long

　　获取系统时间

Private Declare Function timeGetTime Lib "winmm.dll" () As Long

　　数据结构定义：

Private Type BitMapInfoHeader ''文件信息头——BITMAPINFOHEADER
　biSize As Long
　biWidth As Long
　biHeight As Long
　biPlanes As Integer