Get the width and height of a *.jpg image without using a TJPEGImage

Problem/Question/Abstract:

Is there a way to get a Jpeg's height and width without using TJPEGImage? I have over 10000 images that have to be verified each month and using TJPEGImage.LoadFromFile to get the Height and Width is too slow.

Answer:

This might not work with all sorts of *.jpg images:

function GetJpegSize(const FileName: string): TPoint;
var
  fs: TFileStream;
  SegmentPos: Integer;
  SOIcount: Integer;
  x, y: word;
  b: byte;
begin
  fs := TFileStream.Create(FileName, fmOpenRead or fmShareDenyNone);
  try
    fs.Position := 0;
    fs.Read(x, 2);
    if x <> $D8FF then
      raise Exception.Create('Not a Jpeg file');
    SOIcount := 0;
    fs.Position := 0;
    while fs.Position + 7 < fs.Size do
    begin
      fs.Read(b, 1);
      if b = $FF then
      begin
        fs.Read(b, 1);
        if b = $D8 then
          Inc(SOIcount);
        if b = $DA then
          Break;
      end;
    end;
    if b <> $DA then
      raise Exception.Create('Corrupt Jpeg file');
    SegmentPos := -1;
    fs.Position := 0;
    while fs.Position + 7 < fs.Size do
    begin
      fs.Read(b, 1);
      if b = $FF then
      begin
        fs.Read(b, 1);
        if b in [$C0, $C1, $C2] then
        begin
          SegmentPos := fs.Position;
          Dec(SOIcount);
          if SOIcount = 0 then
            Break;
        end;
      end;
    end;
    if SegmentPos = -1 then
      raise Exception.Create('Corrupt Jpeg file');
    if fs.Position + 7 > fs.Size then
      raise Exception.Create('Corrupt Jpeg file');
    fs.Position := SegmentPos + 3;
    fs.Read(y, 2);
    fs.Read(x, 2);
    Result := Point(Swap(x), Swap(y));
  finally
    fs.Free;
  end;
end;