Оформил: DeeCo
Автор: http://www.swissdelphicenter.ch

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' + #0$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);
       FileStream.Read(VertRes, 2); // y axis 
      VertRes := Swap(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' + #0$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;