一直想自己写一个图像处理的软件。在网络上找各种图像处理方面的技术文章。
但是找到的往往不是高深的理论，就是用C++等语言写出来的例程，非常不便。
其实很多时候，我想找的只是一种描述，或者是伪代码，既有利于理解，也有利于改写成任何语言的版本。
近日，我把自己学到的一些图像处理方面的知识写了一个ImageCast的小程序。把自己所掌握的处理技巧作了一个“包装”，感慨于资料收集的不便和学习VB中的点点滴滴。特将算法提供给大家以作参考。希望对于一些和我一样在网上寻觅不获的朋友有所帮主。

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


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
biBitCount As Integer
biCompression As Long
biSizeImage As Long
biXPelsPerMeter As Long
biYPelsPerMeter As Long
biClrUsed As Long
biClrImportant As Long
End Type

Private Type RGBQuad
rgbBlue As Byte
rgbGreen As Byte
rgbRed As Byte
'rgbReserved As Byte
End Type

Private Type BitMapInfo
bmiHeader As BitMapInfoHeader
bmiColors As RGBQuad
End Type
这三个数据结构都是在DIB中不可缺少的。我们不必深究，只是按照顺序复制粘贴直接使用就是了。

过程中用到的全局变量：
Private Const Bits As Long = 32 '颜色深度，这里把所有图像都按照32位来处理
Public Done As Boolean '用于标记一个过程是否结束
Public TimeGet As Long '用于记录输入过程处理所花费的时间
Public TimePut As Long '用于记录输出过程处理所花