从内存流中读取图片给数据库的i字段.txt

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从内存流中读取图片给数据库的i字段 
procedure TForm1.Button5Click(Sender: TObject); 

//保存图像 
var 
strm: TMemoryStream; 
ext: String; 
begin 
if image1.picture.Graphic <> nil then //避免image1中无图像保存出错 
begin 
ext:=extractfileext(openpicturedialog1.FileName ); //取出文件的扩展名 
strm := tmemorystream.Create ; 
try 
image1.Picture.Graphic.SaveToStream(strm); 
adotable1.Edit ; 
strm.Position :=0; 
tblobfield(adotable1.FieldByName('i')).LoadFromStream(strm);//提示bitmap is not valid// 请问该怎么改写 谢谢 


//以下记录保存到数据库的图像格式 
if (uppercase(ext) = '.BMP') then 
adotable1.FieldByName('isbmp').Value := 1 //BMP型图像数据 
else 
if (uppercase(ext) = '.JPG') OR ( uppercase(ext) = '.JPEG') Then 
adotable1.FieldByName('isbmp').Value := 0; //JPEG型图像数据 
adotable1.Post ; 
finally 
strm.Free ; 
Application.MessageBox('保存成功'); 
end; 
end; 
end;