如何判断文件的类型 ( 积分: 50 )

[blue]<br>请问我怎么能判断出来一个文件是BMP还是JPG文件呀<br>最好不要用后缀名判断<br>[/blue]

[blue]<br>请问我怎么能判断出来一个文件是BMP还是JPG文件呀<br>最好不要用后缀名判断<br>[/blue]

取文件的前几个字节<br>Bmp : 42 4d<br>Jpg : FF D8<br>Gif : 47 49 46<br><br><br>procedure TForm1.Button1Click(Sender: TObject);<br>Var<br> &nbsp;s : String;<br> &nbsp;b : Array[0..2] Of Byte;<br> &nbsp;fs : TFileStream;<br>begin<br> &nbsp;If Not OpenDialog1.Execute Then Exit;<br> &nbsp;s := OpenDialog1.FileName;<br> &nbsp;fs := TFileStream.Create(s, fmOpenRead);<br> &nbsp;Try<br> &nbsp; &nbsp;fs.Read(b, 3);<br> &nbsp; &nbsp;Edit1.Text := IntToHex(b[0], 2) + ' ' + IntToHex(b[1], 2) + ' ' + IntToHex(b[2], 2);<br> &nbsp;Finally<br> &nbsp; &nbsp;FreeAndNil(fs);<br> &nbsp;End;<br>end;

接受答案了.