中财网www.cnmeiw.com:一段屏幕抓取的小代码
来源：百度文库 编辑：中财网 时间：2024/04/30 06:07:39
截图软件很多,那么这些软件的功能是如何来实现的呢?我找了个屏幕抓取的小函数供大家参考学习:
procedure ScreenShot(x : integer; y : integer; Width : integer; Height : integer; bm : TBitMap);
var
dc: HDC; lpPal : PLOGPALETTE;
begin
// 检测所需抓屏的区域
if ((Width = 0) OR (Height = 0)) then exit;
bm.Width := Width;
bm.Height := Height;
//获取设备上下文
dc := GetDc(0);
if (dc = 0) then exit;
{do we have a palette device?}
if (GetDeviceCaps(dc, RASTERCAPS) AND
RC_PALETTE = RC_PALETTE) then
begin
{allocate memory for a logical palette}
GetMem(lpPal, sizeof(TLOGPALETTE) + (255 * sizeof(TPALETTEENTRY)));
{zero it out to be neat}
FillChar(lpPal^, sizeof(TLOGPALETTE) + (255 * sizeof(TPALETTEENTRY)), #0);
{fill in the palette version}
lpPal^.palVersion := $300;
{grab the system palette entries}
lpPal^.palNumEntries :=
GetSystemPaletteEntries(dc,0,256,lpPal^.palPalEntry);
if (lpPal^.PalNumEntries <> 0) then
begin
{create the palette}
bm.Palette := CreatePalette(lpPal^);
end;
FreeMem(lpPal, sizeof(TLOGPALETTE) + (255 * sizeof(TPALETTEENTRY)));
end;
{copy from the screen to the bitmap}
BitBlt(bm.Canvas.Handle,0,0,Width,Height,Dc,x,y,SRCCOPY);
{release the screen dc}
ReleaseDc(0, dc);
end;
调用示例：
procedure TForm1.Button1Click(Sender: TObject);
var
tBM : TBitmap;
begin
tBM := TBitmap.Create;
ScreenShot(0,0,Screen.Width,Screen.height,tBM);
tBM.SaveToFile('c:\ScreenShot.BMP');
tBm.FreeImage;
FreeAndNil(tBM);
image1.Picture.LoadFromFile('c:\screenshot.bmp');
end;