HRGN cAppskin::GetBitmapRegion(HBITMAP hBMP, COLORREF cTransparentColor , COLORREF cTolerance , LPRECT lpDestRect)
{
HRGN hRgn = NULL;
RECT rcDest; // Get bitmap size
BITMAP bm;
GetObject(hBMP, sizeof(bm), &bm); if( lpDestRect != NULL )
{
CopyRect( &rcDest, lpDestRect );
}
else
{
rcDest.left = rcDest.top = 0;
rcDest.right = bm.bmWidth;
rcDest.bottom = bm.bmHeight;
} if( !hBMP )
return FALSE; // Create a memory DC inside which we will scan the bitmap content
HDC hMemDC = CreateCompatibleDC(NULL);
if (hMemDC)
{
// Create a 32 bits depth bitmap and select it into the memory DC
BITMAPINFOHEADER RGB32BITSBITMAPINFO = {
sizeof(BITMAPINFOHEADER), // biSize
RECT_WIDTH(rcDest), // biWidth;
RECT_HEIGHT(rcDest), // 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);
StretchBlt(hMemDC, 0, 0, RECT_WIDTH(rcDest), RECT_HEIGHT(rcDest), hDC, 0, 0, bm.bmWidth, bm.bmHeight, SRCCOPY); 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 < bm32.bmHeight; y++)
{
// Scan each bitmap pixel from left to right
for (int x = 0; x < bm32.bmWidth; x++)
{
// Search for a continuous range of "non transparent pixels"
int x0 = x;
LONG *p = (LONG *)p32 + x;
while (x < bm32.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;
}
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