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
|
