位图快速转化成区域

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BMP2RGN

针对各种颜色的HBITMAP转化为region。

HRGN BitmapToRegion (HBITMAP hBmp, COLORREF cTransparentColor = 0, COLORREF cTolerance = 0x101010)

{

    HRGN hRgn = NULL;

    if (hBmp)

    {

        // Create a memory DC inside which we will scan the bitmap content

        HDC hMemDC = CreateCompatibleDC(NULL);

        if (hMemDC)

        {

            // Get bitmap size

            BITMAP bm;

            GetObject(hBmp, sizeof(bm), &bm);

            // Create a 32 bits depth bitmap and select it into the memory DC 

            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;

}