怎么获得这样的信息？

Question

怎么获得这样的信息？谢谢

Answer 1

procedure TForm1.Button1Click(Sender: TObject);
  procedure GetResJpg(JPGFile: string);
  const
    BufferSize = 50;
  var
    Buffer: string;
    Index: integer;
    FileStream: TFileStream;
    HorzRes, VertRes: Word;
    DP: Byte;
    Measure: string;
  begin
    FileStream := TFileStream.Create(JPGFile,
      fmOpenReadWrite);
    try
      SetLength(Buffer, BufferSize);
      FileStream.Read(buffer[1], BufferSize);
      Index := Pos('JFIF' + #$00, buffer);
      if Index > 0 then
      begin
        FileStream.Seek(Index + 6, soFromBeginning);
        FileStream.Read(DP, 1);
        case DP of
          1: Measure := 'DPI'; //Dots Per Inch
          2: Measure := 'DPC'; //Dots Per Cm.
        end;
        FileStream.Read(HorzRes, 2); // x axis
        HorzRes := Swap(HorzRes);
        showmessage( inttostr(HorzRes) ) ;
        FileStream.Read(VertRes, 2); // y axis
        VertRes := Swap(VertRes);
        showmessage( inttostr(VertRes) ) ;
      end
    finally
      FileStream.Free;
    end;
  end;
  procedure SetResJpg(name: string; dpix, dpiy: Integer);
  const
    BufferSize = 50;
    DPI = 1; //inch
    DPC = 2; //cm
  var
    Buffer: string;
    index: INTEGER;
    FileStream: TFileStream;
    xResolution: WORD;
    yResolution: WORD;
    _type: Byte;
  begin
    FileStream := TFileStream.Create(name,
      fmOpenReadWrite);
    try
      SetLength(Buffer, BufferSize);
      FileStream.Read(buffer[1], BufferSize);
      index := POS('JFIF' + #$00, buffer);
      if index > 0
        then begin
        FileStream.Seek(index + 6, soFromBeginning);
        _type := DPI;
        FileStream.write(_type, 1);
        xresolution := swap(dpix);
        FileStream.write(xresolution, 2);
        yresolution := swap(dpiy);
        FileStream.write(yresolution, 2);
      end
    finally
      FileStream.Free;
    end;
  end;
begin
SetResJpg( 'C:\123.jpg',96,96 );
GetResJpg( 'c:\123.jpg' );
end;