判断头几个字节：
function IsJpegFile(FileName: string): Boolean;
const
RightBuf : array[0..3] of Byte = ($FF,$D8,$FF,$D9);
var
Buf: array[0..3] of Byte;
begin
FillChar(Buf, 4, 0);
with TFileStream.Create(FileName, 0) do begin
Position := 0;
ReadBuffer(Buf[0], 2);
Position := Size-2;
ReadBuffer(Buf[2], 2);
Free;
end;
Result := CompareMem(@RightBuf[0], @Buf[0], 4);
end;
procedure TForm1.Button1Click(Sender: TObject);//测试
begin
if Self.OpenDialog1.Execute then
if IsJpegFile(Self.OpenDialog1.FileName) then
Showmessage(‘Is Jpg File‘);
end;
Delphi判断一个文件是不是JPG图片
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