我自己也没有用过，看来是更加麻烦，
下面有一个例子，我也没有仔细读过
（Copy From SkinForm.pas(Author: Xue Huai Qing [xhq@writeme.com])）
// This function programmed by Eddie Shipman
function Bitmap2Region( hBmp: TBitmap; TransColor: TColor; Tolerance: TColor): HRGN;
const
ALLOC_UNIT = 100;
var
MemDC, DC: HDC;
BitmapInfo: TBitmapInfo;
hbm32, holdBmp, holdMemBmp: HBitmap;
pbits32 : Pointer;
bm32 : BITMAP;
maxRects: DWORD;
hData: HGLOBAL;
pData: PRgnData;
b, LR, LG, LB, HR, HG, HB: Byte;
p32: pByte;
x, x0, y: integer;
p: pLongInt;
pr: PRect;
h: HRGN;
function MinByte(B1, B2: byte): byte;
begin
if B1 < B2 then
Result := B1
else
Result := B2;
end;
begin
Result := 0;
if hBmp <> nil then
begin
{ Create a memory DC inside which we will scan the bitmap contents }
MemDC := CreateCompatibleDC(0);
if MemDC <> 0 then
begin
{ Create a 32 bits depth bitmap and select it into the memory DC }
with BitmapInfo.bmiHeader do
begin
biSize := sizeof(TBitmapInfoHeader);
biWidth := hBmp.Width;
biHeight := hBmp.Height;
biPlanes := 1;
biBitCount := 32;
biCompression := BI_RGB; { (0) uncompressed format }
biSizeImage := 0;
biXPelsPerMeter := 0;
biYPelsPerMeter := 0;
biClrUsed := 0;
biClrImportant := 0;
end;
hbm32 := CreateDIBSection(MemDC, BitmapInfo, DIB_RGB_COLORS, pbits32,0, 0);
if hbm32 <> 0 then
begin
holdMemBmp := SelectObject(MemDC, hbm32);
{
Get how many bytes per row we have for the bitmap bits
(rounded up to 32 bits)
}
GetObject(hbm32, SizeOf(bm32), @bm32);
while (bm32.bmWidthBytes mod 4) > 0 do
inc(bm32.bmWidthBytes);
DC := CreateCompatibleDC(MemDC);
{ Copy the bitmap into the memory DC }
holdBmp := SelectObject(DC, hBmp.Handle);
BitBlt(MemDC, 0, 0, hBmp.Width, hBmp.Height, DC, 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
}
maxRects := ALLOC_UNIT;
hData := GlobalAlloc(GMEM_MOVEABLE, sizeof(TRgnDataHeader) +
SizeOf(TRect) * maxRects);
pData := GlobalLock(hData);
pData^.rdh.dwSize := SizeOf(TRgnDataHeader);
pData^.rdh.iType := RDH_RECTANGLES;
pData^.rdh.nCount := 0;
pData^.rdh.nRgnSize := 0;
SetRect(pData^.rdh.rcBound, MaxInt, MaxInt, 0, 0);
{ Keep on hand highest and lowest values for the "transparent" pixel }
LR := GetRValue(ColorToRGB(TransColor));
LG := GetGValue(ColorToRGB(TransColor));
LB := GetBValue(ColorToRGB(TransColor));
{ Add the value of the tolerance to the "transparent" pixel value }
HR := MinByte($FF, LR + GetRValue(ColorToRGB(Tolerance)));
HG := MinByte($FF, LG + GetGValue(ColorToRGB(Tolerance)));
HB := MinByte($FF, LB + GetBValue(ColorToRGB(Tolerance)));
{
Scan each bitmap row from bottom to top,
the bitmap is inverted vertically
}
p32 := bm32.bmBits;
inc(PChar(p32), (bm32.bmHeight - 1) * bm32.bmWidthBytes);
for y := 0 to hBmp.Height-1 do
begin
{ Scan each bitmap pixel from left to right }
x := -1;
while x+1 < hBmp.Width do
begin
inc(x);
{ Search for a continuous range of "non transparent pixels" }
x0 := x;
p := PLongInt(p32);
inc(PChar(p), x * SizeOf(LongInt));
while x < hBmp.Width do
begin
b := GetBValue(p^); // Changed from GetRValue(p^)
if (b >= LR) and (b <= HR) then
begin
b := GetGValue(p^); // Left alone
if (b >= LG) and (b <= HG) then
begin
b := GetRValue(p^); // Changed from GetBValue(p^)
if (b >= LB) and (b <= hb) then
{ This pixel is "transparent" }
break;
end;
end;
inc(PChar(p), SizeOf(LongInt));
inc(x);
end;
if x > x0 then
begin
{
Add the pixels (x0, y) to (x, y+1) as a new rectangle in
the region
}
if pData^.rdh.nCount >= maxRects then
begin
GlobalUnlock(hData);
inc(maxRects, ALLOC_UNIT);
hData := GlobalReAlloc(hData, SizeOf(TRgnDataHeader) +
SizeOf(TRect) * maxRects, GMEM_MOVEABLE);
pData := GlobalLock(hData);
Assert(pData <> NIL);
end;
pr := @pData^.Buffer[pData^.rdh.nCount * SizeOf(TRect)];
SetRect(pr^, x0, y, x, y+1);
if x0 < pData^.rdh.rcBound.Left then
pData^.rdh.rcBound.Left := x0;
if y < pData^.rdh.rcBound.Top then
pData^.rdh.rcBound.Top := y;
if x > pData^.rdh.rcBound.Right then
pData^.rdh.rcBound.Left := x;
if y+1 > pData^.rdh.rcBound.Bottom then
pData^.rdh.rcBound.Bottom := y+1;
inc(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 then
begin
h := ExtCreateRegion(NIL, SizeOf(TRgnDataHeader) +
(SizeOf(TRect) * maxRects), pData^);
Assert(h <> 0);
if Result <> 0 then
begin
CombineRgn(Result, Result, h, RGN_OR);
DeleteObject(h);
end else
Result := h;
pData^.rdh.nCount := 0;
SetRect(pData^.rdh.rcBound, MaxInt, MaxInt, 0, 0);
end;
end;
end;
{
Go to next row (remember, the bitmap is inverted vertically)
that is why we use DEC!
}
Dec(PChar(p32), bm32.bmWidthBytes);
end;
{ Create or extend the region with the remaining rectangle }
h := ExtCreateRegion(NIL, SizeOf(TRgnDataHeader) +
(SizeOf(TRect) * maxRects), pData^);
Assert(h <> 0);
if Result <> 0 then
begin
CombineRgn(Result, Result, h, RGN_OR);
DeleteObject(h);
end else
Result := h;
{ Clean up }
GlobalFree(hData);
SelectObject(DC, holdBmp);
DeleteDC(DC);
DeleteObject(SelectObject(MemDC, holdMemBmp));
end;
end;
DeleteDC(MemDC);
end;
end;
