怎么样通过DELPHI实现摄像头拍照？

procedure Tfrm1.Button2Click(Sender: TObject);
Var
jpeg: TJPEGImage;
bmp: TBitmap;
MyStm:TMemoryStream;
strfilename,strcard:String;
begin
inherited;
strfilename:=extractfilepath(Application.ExeName);
with DBEdit12.DataSource.DataSet do
begin

if not VideoCap1.SaveAsDIB then
begin
ShowMessage('拍摄照片失败');
Abort;
end;//

bmp:= TBitmap.Create;
try
bmp.LoadFromFile(strfilename+ 'Capture.bmp' );
MyStm:=TMemoryStream.Create;
jpeg:= TJPEGImage.Create;
try
jpeg.Assign( bmp );
jpeg.compress;
jpeg.SaveTofile( strfilename+'Capture.jpg');
strfilename:=strfilename+'Capture.jpg';
jpeg.LoadFromFile(strfilename);
jpeg.SaveToStream(MyStm);
MyStm.Position:=0;
OpenQry(query1,'select count(1) as cnt from tb_photo where card_no='''+strcard+'''');//先查找是否有此卡号
OpenQry(pubqry,'select * from tb_photo where card_no='''+strcard+'''');//打开卡号数据表
{OpenQry是自定义打开数据表的函数
OpenQry(qry1:TQuery,ssql:String);
begin
with qry1 do
beign
if active then
close;
sql.clear;
sql.add(ssql);
try
open
catch
on E: Exception do ErrorDialog(E.Message, E.HelpContext);
end;//try
end;
end;
}
with query1 do
begin
if pubqry.Fields[0].AsInteger >0 then //先判断此卡号的图片是否存在，若存在，替换；否则，插入。
Edit
else
Insert;

FieldByName('card_no').AsString :=strcard;
TBlobField(FieldByName('photo')).LoadFromStream(MyStm);
Post; //统一提交
end;//with
finally
MyStm.Free;
jpeg.free;
end; //try
finally
bmp.free;
end;//try
end;//with
end;
//请首先下载TVideoCap控件