MFC 创建不规则窗体

//准备两张位图，一张位图为彩色位图，是要作为窗体背景的图片，另一张则为黑白图，黑色是窗体最后要镂空的部分，白色为显示区域

//关键代码：根据一张黑白位图获取Rgn区域

HRGN CMyDlg::BitmapToRegion(HBITMAP hBmp, COLORREF cTransparentColor, COLORREF cTolerance)
{
HRGN hRgn = NULL;

if (hBmp)
{
HDC hMemDC = CreateCompatibleDC(NULL);
if (hMemDC)
{
BITMAP bm;
GetObject(hBmp, sizeof(bm), &bm);

//创建一个32位色的位图，并选进内存设备环境
BITMAPINFOHEADER RGB32BITSBITMAPINFO = {
sizeof(BITMAPINFOHEADER),		// biSize
bm.bmWidth,					// biWidth;
bm.bmHeight,				// biHeight;
1,							// biPlanes;
32,							// biBitCount
BI_RGB,						// biCompression;
0,							// biSizeImage;
0,							// biXPelsPerMeter;
0,							// biYPelsPerMeter;
0,							// biClrUsed;
0							// biClrImportant;
};
VOID * pbits32;
HBITMAP hbm32 = CreateDIBSection(hMemDC,(BITMAPINFO *)&RGB32BITSBITMAPINFO, DIB_RGB_COLORS, &pbits32, NULL, 0);
if (hbm32)
{
HBITMAP holdBmp = (HBITMAP)SelectObject(hMemDC, hbm32);

// Create a DC just to copy the bitmap into the memory DC
HDC hDC = CreateCompatibleDC(hMemDC);
if (hDC)
{
// Get how many bytes per row we have for the bitmap bits (rounded up to 32 bits)
BITMAP bm32;
GetObject(hbm32, sizeof(bm32), &bm32);
while (bm32.bmWidthBytes % 4)
bm32.bmWidthBytes++;

// Copy the bitmap into the memory DC
HBITMAP holdBmp = (HBITMAP)SelectObject(hDC, hBmp);
BitBlt(hMemDC, 0, 0, bm.bmWidth, bm.bmHeight, hDC, 0, 0, SRCCOPY);

// For better performances, we will use the ExtCreateRegion() function to create the
// region. This function take a RGNDATA structure on entry. We will add rectangles by
// amount of ALLOC_UNIT number in this structure.
#define ALLOC_UNIT	100
DWORD maxRects = ALLOC_UNIT;
HANDLE hData = GlobalAlloc(GMEM_MOVEABLE, sizeof(RGNDATAHEADER) + (sizeof(RECT) * maxRects));
RGNDATA *pData = (RGNDATA *)GlobalLock(hData);
pData->rdh.dwSize = sizeof(RGNDATAHEADER);
pData->rdh.iType = RDH_RECTANGLES;
pData->rdh.nCount = pData->rdh.nRgnSize = 0;
SetRect(&pData->rdh.rcBound, MAXLONG, MAXLONG, 0, 0);

// Keep on hand highest and lowest values for the "transparent" pixels
BYTE lr = GetRValue(cTransparentColor);
BYTE lg = GetGValue(cTransparentColor);
BYTE lb = GetBValue(cTransparentColor);
BYTE hr = min(0xff, lr + GetRValue(cTolerance));
BYTE hg = min(0xff, lg + GetGValue(cTolerance));
BYTE hb = min(0xff, lb + GetBValue(cTolerance));

// Scan each bitmap row from bottom to top (the bitmap is inverted vertically)
BYTE *p32 = (BYTE *)bm32.bmBits + (bm32.bmHeight - 1) * bm32.bmWidthBytes;
for (int y = 0; y < bm.bmHeight; y++)
{
// Scan each bitmap pixel from left to right
for (int x = 0; x < bm.bmWidth; x++)
{
// Search for a continuous range of "non transparent pixels"
int x0 = x;
LONG *p = (LONG *)p32 + x;
while (x < bm.bmWidth)
{
BYTE b = GetRValue(*p);
if (b >= lr && b <= hr)
{
b = GetGValue(*p);
if (b >= lg && b <= hg)
{
b = GetBValue(*p);
if (b >= lb && b <= hb)
// This pixel is "transparent"
break;
}
}
p++;
x++;
}

if (x > x0)
{
// Add the pixels (x0, y) to (x, y+1) as a new rectangle in the region
if (pData->rdh.nCount >= maxRects)
{
GlobalUnlock(hData);
maxRects += ALLOC_UNIT;
hData = GlobalReAlloc(hData, sizeof(RGNDATAHEADER) + (sizeof(RECT) * maxRects), GMEM_MOVEABLE);
pData = (RGNDATA *)GlobalLock(hData);
}
RECT *pr = (RECT *)&pData->Buffer;
SetRect(&pr[pData->rdh.nCount], x0, y, x, y+1);
if (x0 < pData->rdh.rcBound.left)
pData->rdh.rcBound.left = x0;
if (y < pData->rdh.rcBound.top)
pData->rdh.rcBound.top = y;
if (x > pData->rdh.rcBound.right)
pData->rdh.rcBound.right = x;
if (y+1 > pData->rdh.rcBound.bottom)
pData->rdh.rcBound.bottom = y+1;
pData->rdh.nCount++;

// On Windows98, ExtCreateRegion() may fail if the number of rectangles is too
// large (ie: > 4000). Therefore, we have to create the region by multiple steps.
if (pData->rdh.nCount == 2000)
{
HRGN h = ExtCreateRegion(NULL, sizeof(RGNDATAHEADER) + (sizeof(RECT) * maxRects), pData);
if (hRgn)
{
CombineRgn(hRgn, hRgn, h, RGN_OR);
DeleteObject(h);
}
else
hRgn = h;
pData->rdh.nCount = 0;
SetRect(&pData->rdh.rcBound, MAXLONG, MAXLONG, 0, 0);
}
}
}

// Go to next row (remember, the bitmap is inverted vertically)
p32 -= bm32.bmWidthBytes;
}

// Create or extend the region with the remaining rectangles
HRGN h = ExtCreateRegion(NULL, sizeof(RGNDATAHEADER) + (sizeof(RECT) * maxRects), pData);
if (hRgn)
{
CombineRgn(hRgn, hRgn, h, RGN_OR);
DeleteObject(h);
}
else
hRgn = h;

// Clean up
GlobalFree(hData);
SelectObject(hDC, holdBmp);
DeleteDC(hDC);
}
DeleteObject(SelectObject(hMemDC, holdBmp));
}
DeleteDC(hMemDC);
}
}
return hRgn;
}

//在对话框初始化或窗口创建时中添加以下代码

BOOL CMyDlg::OnInitDialog()
{

// TODO: 在此添加额外的初始化代码
CBitmap bmp;
if(bmp.LoadBitmap(IDB_BITMAP2))
{
HRGN rgn;
rgn = BitmapToRegion((HBITMAP)bmp, RGB(0,0,0));//RGB(0,0,0)纯黑色作为透明色，是需要裁剪掉的区域
//设置窗体的有效区域
SetWindowRgn(rgn, TRUE);
bmp.DeleteObject();
}
return TRUE;  // 除非将焦点设置到控件，否则返回 TRUE
}