VC 位图背景透明显示

以前还没有注意到透明的问题，记下来

http://www.vckbase.com/document/viewdoc/?id=532
这里面有详细的说明

1

BOOL CAboutDlg::OnInitDialog()

{

CDialog::OnInitDialog();

// TODO: Add extra initialization here

m_bmpLogo.LoadBitmap(IDB_BITMAP_LOGO);

return TRUE; // return TRUE unless you set the focus to a control

// EXCEPTION: OCX Property Pages should return FALSE

}

2

void CAboutDlg::OnPaint()

{

CPaintDC dc(this); // device context for painting

BITMAP bm;

COLORREF crMask = RGB(0xFF,0xFF,0xFF);

m_bmpLogo.GetBitmap(&bm);

int nWidth = bm.bmWidth;

int nHeight = bm.bmHeight;

CDC ImageDC;

ImageDC.CreateCompatibleDC(&dc);

CBitmap *pOldImageBMP = ImageDC.SelectObject(&m_bmpLogo);

TransparentBlt2(dc.m_hDC,110,30,nWidth,nHeight,ImageDC.m_hDC,0,0,nWidth,nHeight,crMask);

ImageDC.SelectObject(pOldImageBMP);

// Do not call CDialog::OnPaint() for painting messages

}

3

void CAboutDlg::TransparentBlt2( HDC hdcDest, // 目标DC

int nXOriginDest, // 目标X偏移

int nYOriginDest, // 目标Y偏移

int nWidthDest, // 目标宽度

int nHeightDest, // 目标高度

HDC hdcSrc, // 源DC

int nXOriginSrc, // 源X起点

int nYOriginSrc, // 源Y起点

int nWidthSrc, // 源宽度

int nHeightSrc, // 源高度

UINT crTransparent // 透明色,COLORREF类型

)

{

HBITMAP hOldImageBMP, hImageBMP = CreateCompatibleBitmap(hdcDest, nWidthDest, nHeightDest); // 创建兼容位图

HBITMAP hOldMaskBMP, hMaskBMP = CreateBitmap(nWidthDest, nHeightDest, 1, 1, NULL); // 创建单色掩码位图

HDC hImageDC = CreateCompatibleDC(hdcDest);

HDC hMaskDC = CreateCompatibleDC(hdcDest);

hOldImageBMP = (HBITMAP)SelectObject(hImageDC, hImageBMP);

hOldMaskBMP = (HBITMAP)SelectObject(hMaskDC, hMaskBMP);

// 将源DC中的位图拷贝到临时DC中

if (nWidthDest == nWidthSrc && nHeightDest == nHeightSrc)

BitBlt(hImageDC, 0, 0, nWidthDest, nHeightDest, hdcSrc, nXOriginSrc, nYOriginSrc, SRCCOPY);

else

StretchBlt(hImageDC, 0, 0, nWidthDest, nHeightDest,

hdcSrc, nXOriginSrc, nYOriginSrc, nWidthSrc, nHeightSrc, SRCCOPY);

// 设置透明色

SetBkColor(hImageDC, crTransparent);

// 生成透明区域为白色，其它区域为黑色的掩码位图

BitBlt(hMaskDC, 0, 0, nWidthDest, nHeightDest, hImageDC, 0, 0, SRCCOPY);

// 生成透明区域为黑色，其它区域保持不变的位图

SetBkColor(hImageDC, RGB(0,0,0));

SetTextColor(hImageDC, RGB(255,255,255));

BitBlt(hImageDC, 0, 0, nWidthDest, nHeightDest, hMaskDC, 0, 0, SRCAND);

// 透明部分保持屏幕不变，其它部分变成黑色

SetBkColor(hdcDest,RGB(255,255,255));

SetTextColor(hdcDest,RGB(0,0,0));

BitBlt(hdcDest, nXOriginDest, nYOriginDest, nWidthDest, nHeightDest, hMaskDC, 0, 0, SRCAND);

// "或"运算,生成最终效果

BitBlt(hdcDest, nXOriginDest, nYOriginDest, nWidthDest, nHeightDest, hImageDC, 0, 0, SRCPAINT);

// 清理、恢复

SelectObject(hImageDC, hOldImageBMP);

DeleteDC(hImageDC);

SelectObject(hMaskDC, hOldMaskBMP);

DeleteDC(hMaskDC);

DeleteObject(hImageBMP);

DeleteObject(hMaskBMP);

}