以下程序,提取屏幕没问题,可是抓摄像头的图片就有问题,抓出来的大小是0,请各位大虾帮忙.
function TfrmServer.snapScreen():boolean;
var
  bmpscreen: Tbitmap;
  jpegscreen: Tjpegimage;
  FullscreenCanvas: TCanvas;
  dc: HDC;
  sourceRect, destRect: TRect;
begin
  result:=false;
  bmpscreen := Tbitmap.create;
  //创建储存Jpeg格式的对象
  jpegscreen := Tjpegimage.Create;
  if zxpm='show' then  begin
        //得到屏幕设备
        dc := getdc(0);
        //创建画布句柄
        fullscreencanvas := Tcanvas.Create;
        fullscreencanvas.Handle := dc;
        //创建存储位图对象
        bmpscreen.Width := screen.Width;
        bmpscreen.Height := screen.Height;
        sourcerect := rect(0, 0, screen.Width, screen.Height);
        destrect := rect(0, 0, screen.Width, screen.Height);
        //将屏幕图象抓取到bmpScreen位图中
        bmpscreen.Canvas.CopyRect(sourcerect, fullscreenCanvas, destrect);
        end
  else begin
     SampleGrabber1.GetBitmap(bmpscreen);\\将摄像头图像转成图片
  end;
  //将图象压缩成Jpeg格式，保存到JpegStream内存流中。
  jpegscreen.Assign(bmpscreen);
  jpegscreen.CompressionQuality := 40;
  jpegscreen.SaveToStream(jpegStream);
  jpegstream.Position := 0;
  LeftSize := jpegStream.Size;
  //释放创建的对象
  if zxpm='show' then  begin
     FullscreenCanvas.Free;
     ReleaseDC(0, DC);
  end;
  bmpscreen.Free;
  jpegscreen.Free;
  result:=true;
end;