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如何用VB6创建透明图象
创建透明图象的五个必须的步骤：
准备两个位图文件，一个作背景，一个是将要成为透明图象的源位图。
1、 取得源位图的长、宽数据，依此数据保存一块和源位图一样大小的背景位图，源位图将要在这块背景位图上绘制。通过用白色像素显示位图的透明区域，黑色像素显示位图的不透明区域，创建决定位图透明的单色掩码。
2、单色掩码像素与所用的背景位图进行二进制“与”（and）位操作，不透明的区域，背景显示黑色。
3、用第一步所做的单色掩码建立一个反向拷贝，再用这个反向拷贝与所用的源位图进行二进制“与”（and）位操作，源位图透明的区域将显示黑色
4、用第二步修改过的背景和第三步修改的源位图进行二进制“异或”（Xor）位操作，这时可以透过透明位图看到背景。
5、把结果位图复制给背景
应用实例：
创建包含一个 CommandButton 控件和两个PictureBox控件的 窗体Form1。创建一个模块（在 "工程”菜单中单击“添加模块”）。
给窗体增加下列控件，设置相关的属性值：
控件 Name Property Settings
-----------------------------------------------------------------
PictureBox pictSource Picture ="C:\Flower_Vine.bmp"
PictureBox pictDest Picture ="C:\Stones_Blue.bmp"
Command button Command1 Caption ="透明图象"
---- 将下面的代码粘贴到窗体的声明部分中，
---- Option Explicit @# 这段代码调用过程Transparent()复制源位图到目标（背景）picturebox控件， @# 并将其变成透明，使人们可以看到后面的背景图象。
Sub command1_Click()
Call Transparent(PictSource.Picture.Handle, PictDest,
10, 10, QBColor(15))
End Sub
---- 将下面的代码粘贴到模块的声明部分中，
Option Explicit
---- @# 由于要读取位图的基本信息，所以首先要定义一个BITMAP结构的变量，然后
---- @# 利用这一变量来接受位图的基本信息。
@#
Type Bitmap
Type As Long @# 位图类型
Width As Long @#宽度
Height As Long @#高度
WidthBytes As Long @#多少二进制位构成一个存储单位
Planes As Integer @#调色板数
BitsPixel As Integer @#每一个Pixel所占用的二进制位数
Bits As Long @#二进制位数据的起始位置
End Type
@#API 函数说明
Declare Function GetObject Lib "gdi32"
Alias "GetObjectA" (ByVal hObject As _
Long, ByVal nCount As Long, lpObject As Any) As Long
@#经由对象的Handle取得对象数据结构的API函数
Declare Function CreateCompatibleDC Lib "gdi32"
(ByVal hdc As Long) As Long @#
此函数将图象绘制到存储器中可避免直
@#接将图象绘制到屏幕上而造成图象闪烁
Declare Function CreateBitmap Lib "gdi32"
(ByVal nWidth As Long, _
ByVal nHeight As Long, ByVal nPlanes
As Long, _
ByVal nBitCount As Long, lpBits As Any)
As Long @#建立位图对象
Declare Function CreateCompatibleBitmap Lib
"gdi32" (ByVal hdc As Long, _
ByVal nWidth As Long, ByVal nHeight As Long)
As Long @#建立兼容性的位图
Declare Function BitBlt Lib "gdi32"
(ByVal hDestDC As Long, _
ByVal x As Long, ByVal y As Long, ByVal
nWidth As Long, _
ByVal nHeight As Long, ByVal hsourceDC As Long,
ByVal xSrc As Long, _
ByVal ySrc As Long, ByVal dwRop As Long) As Long @#图象转移
Declare Function SetBkColor Lib "gdi32" (ByVal hdc As Long,
ByVal crColor As Long) As Long
Declare Function DeleteDC Lib "gdi32" (ByVal hdc As Long)
As Long @#删除存储器DC
Declare Function SelectObject Lib "gdi32" (ByVal hdc As Long,
ByVal hObject As Long) As Long @#为DC选用对象
Declare Function DeleteObject Lib "gdi32" (ByVal hObject As
Long) As Long @#删除位图对象
---- 过程Transparent() 复制源位图到背景的任意 X,Y 位置，使这一区域变成透明。Transparent()接受五个参数：一个将要变成透明的源位图,一个目标 picturebox控件 (PictDest), 一个RGB颜色值，另两个是你想放置原位图的目的地坐标(destX 和 destY，以像素为单位)。
Sub Transparent(ByVal sourceBmp As Long, dest As Control, ByVal _
destX As Integer, ByVal destY As Integer, ByVal TransColor As Long)
Const PIXEL = 3
Dim sourceDC As Long @#源位图
Dim destScale As Long
Dim maskDC As Long @#mask位图 (monochrome)
Dim saveDC As Long @#源位图的备份
Dim resultDC As Long @#源位图与背景的合并
Dim invDC As Long @#Mask位图的反向图
Dim OrigColor As Long @#背景色
Dim Success As Long @#调用 Windows API的结果
Dim bmp As Bitmap @#原位图的数据结构说明
Dim hResultBmp As Long @#源与背景的位图合并
Dim hSaveBmp As Long @#原位图的拷贝
Dim hSrcPrevBmp As Long
Dim hDestPrevBmp As Long
Dim hInvBmp As Long @#反转掩码位图 (monochrome)
Dim hPrevBmp As Long
Dim hInvPrevBmp As Long
Dim hSavePrevBmp As Long
Dim hMaskBmp As Long
Dim hMaskPrevBmp As Long
destScale = dest.ScaleMode @#保存 ScaleMode以便后面恢复
dest.ScaleMode = PIXEL @#设置 ScaleMode
sourceDC = CreateCompatibleDC(dest.hdc) @#建立存储器DC
saveDC = CreateCompatibleDC(dest.hdc) @#建立存储器DC
invDC = CreateCompatibleDC(dest.hdc) @#建立存储器DC
maskDC = CreateCompatibleDC(dest.hdc) @#建立存储器DC
resultDC = CreateCompatibleDC(dest.hdc) @#建立存储器DC
@#接受源位图得到它的的宽度和长度 (bmp.Width ， bmp.Height)
Success = GetObject(sourceBmp, Len(bmp), bmp)
@#创建单色掩码位图
hMaskBmp = CreateBitmap(bmp.Width, bmp.Height, 1, 1, ByVal 0&)
hInvBmp = CreateBitmap(bmp.Width, bmp.Height, 1, 1, ByVal 0&)
hResultBmp = CreateCompatibleBitmap(dest.hdc, bmp.Width, _
bmp.Height)
hSaveBmp = CreateCompatibleBitmap(dest.hdc, bmp.Width, _
bmp.Height)
hSrcPrevBmp = SelectObject(sourceDC, sourceBmp)
hSavePrevBmp = SelectObject(saveDC, hSaveBmp)
hMaskPrevBmp = SelectObject(maskDC, hMaskBmp)
hInvPrevBmp = SelectObject(invDC, hInvBmp)
hDestPrevBmp = SelectObject(resultDC, hResultBmp) @#选择位图
Success = BitBlt(saveDC, 0, 0, bmp.Width, bmp.Height, sourceDC, _
0, 0, vbSrcCopy) @#制作源位图的拷贝以便后面恢复
OrigColor = SetBkColor(sourceDC, TransColor)
Success = BitBlt(maskDC, 0, 0, bmp.Width, bmp.Height, sourceDC, _
0, 0, vbSrcCopy)
TransColor = SetBkColor(sourceDC, OrigColor)
Success = BitBlt(invDC, 0, 0, bmp.Width, bmp.Height, maskDC, _
0, 0, vbNotSrcCopy)
@#拷贝背景图并创建最终的透明位图
Success = BitBlt(resultDC, 0, 0, bmp.Width, bmp.Height, _
dest.hdc, destX, destY, vbSrcCopy)
Success = BitBlt(resultDC, 0, 0, bmp.Width, bmp.Height, _
maskDC, 0, 0, vbSrcAnd)
Success = BitBlt(sourceDC, 0, 0, bmp.Width, bmp.Height, invDC, _
0, 0, vbSrcAnd)
Success = BitBlt(resultDC, 0, 0, bmp.Width, bmp.Height, _
sourceDC, 0, 0, vbSrcInvert)
Success = BitBlt(dest.hdc, destX, destY, bmp.Width, bmp.Height, _
resultDC, 0, 0, vbSrcCopy) @#在背景上显示透明位图
Success = BitBlt(sourceDC, 0, 0, bmp.Width, bmp.Height, saveDC, _
0, 0, vbSrcCopy) @#恢复位图
@#选择对象以便释放
hPrevBmp = SelectObject(resultDC, hDestPrevBmp)
hPrevBmp = SelectObject(sourceDC, hSrcPrevBmp)
hPrevBmp = SelectObject(saveDC, hSavePrevBmp)
hPrevBmp = SelectObject(invDC, hInvPrevBmp)
hPrevBmp = SelectObject(maskDC, hMaskPrevBmp)
@#释放资源
Success = DeleteDC(saveDC)
Success = DeleteDC(invDC)
Success = DeleteDC(resultDC)
Success = DeleteObject(hSaveBmp)
Success = DeleteObject(hMaskBmp)
Success = DeleteObject(hInvBmp)
Success = DeleteDC(sourceDC)
Success = DeleteDC(maskDC)
Success = DeleteObject(hResultBmp)
dest.ScaleMode = destScale @#恢复 ScaleMode
End Sub
