type
  TResID = record
    ResInt: integer;
    ResString: AnsiString;
    isInteger: boolean;
end;

type
   PResID = ^TResID;

function EnumResIcon(Module: THandle; resType: PChar; HasIconGroup: PBool): bool; stdcall;
begin
  if resType = RT_GROUP_ICON then
  begin
    HasIconGroup^:= true;
    result:= false;
  end
  else
    result:= true;
end;

function EnumIconNames(Module: THandle; ResType, ResName: PChar; ResID: PResID): bool; stdcall;
begin
  if integer(resName)< $FFFF then
  begin
    ResID^.ResInt:= integer(ResName);
    ResID^.isInteger:= true;
  end
  else
  begin
    SetString(ResID^.ResString, ResName, Length(ResName));
    ResID^.isInteger:= false;
  end;
  result:= false;
end;

function HasIcoSize(IconPfad: AnsiString; IconSize: Byte): boolean;
var
  IconNr, IconAnzahl: byte;
  Next: cardinal;
  IconStream: TFileStream;
  ResStream: TResourceStream;
  Buffer: array of byte;
  FileExt: AnsiString;
  Lib: THandle;
  HasIcons: LongBool;
  ResID: TResID;
begin
  result:= false;
  if FileExists(IconPfad) then
  begin
    FileExt:= UpperCase(ExtractFileExt(IconPfad));
    if (FileExt= '.ICO') or (FileExt= '.CUR') then
    begin
      IconStream:= TFileStream.Create(IconPfad, fmOpenRead);
      try
        if IconStream.Seek(4, soFromCurrent)= 4 then
        if IconStream.Read(IconAnzahl, 1)= 1 then
        if IconStream.Seek(0, soFromBeginning)= 0 then
        begin
          Next:= 6;
          setlength(Buffer, IconAnzahl* 16);
          if IconStream.Read(Buffer[0], length(Buffer))= Length(Buffer) then
            for IconNr:= 1 to IconAnzahl do
            begin
              if (Buffer[Next]= IconSize) and (Buffer[Next+ 1]= IconSize) then
              begin
                result:= true;
                break;
              end;
              inc(Next, 16);
            end;
        end;
      finally
        IconStream.Free;
      end;
    end
    else
    begin
      Lib:= LoadLibraryEx(PChar(IconPfad), 0, LOAD_LIBRARY_AS_DATAFILE);
      if Lib<> 0 then
      try
        HasIcons:= false;
        EnumResourceTypes(Lib, @EnumResIcon, integer(@HasIcons));
        if HasIcons then
        begin
          EnumResourceNames(Lib, RT_GROUP_ICON, @EnumIconNames, integer(@ResID));
          if ResID.isInteger then
            ResStream:= TResourceStream.CreateFromID(Lib, ResID.ResInt, RT_GROUP_ICON)
          else
            ResStream:= TResourceStream.Create(Lib, ResID.ResString, RT_GROUP_ICON);
          try
            IconAnzahl:= byte(pointer(cardinal(ResStream.Memory)+ 4)^);
            Next:= 6;
            for IconNr:= 1 to IconAnzahl do
            begin
              if (byte(pointer(cardinal(ResStream.Memory)+ Next)^)= IconSize) and
                (byte(pointer(cardinal(ResStream.Memory)+ Next+ 1)^)= IconSize) then
              begin
                result:= true;
                break;
              end;
              inc(Next, 14);
            end;
          finally
            ResStream.Free;
          end;
        end;
      finally
        windows.FreeLibrary(Lib);
      end;
    end;
  end;
end;



procedure TForm1.Button1Click(Sender: TObject);
begin
  if OpenDialog1.execute then
  if HasIcoSize(OpenDialog1.FileName, 48)then
    Showmessage('Die Datei hat Icone mit mit einer Größe von 48 X 48')
  else
    Showmessage('Die Datei hat KEINE Icone mit mit einer Größe von 48 X 48')
end;