Get icon for known file type

GetIconByFileExt.pas

uses Winapi.ShellAPI;

function GetIconByFileExt(aFileExt: string): TBytes;
var C: TIcon;
    N: SHFILEINFO;
    S: TBytesStream;
begin
  C := TIcon.Create;
  try
    Win32Check(Succeeded(
      SHGetFileInfo(
        PChar(aFileExt),
        FILE_ATTRIBUTE_NORMAL,
        N,
        SizeOf(N),
        SHGFI_ICON or SHGFI_SMALLICON or
        SHGFI_SYSICONINDEX or SHGFI_USEFILEATTRIBUTES
      )
    ));
    C.Handle := N.hIcon;
    S := TBytesStream.Create;
    try
      C.SaveToStream(S);
      Result := S.Bytes;
    finally
      S.Free;
    end;
    Win32Check(DestroyIcon(N.hIcon));
  finally
    C.Free;
  end;
end;

var S: TStream;
begin
  S := TBytesStream.Create(GetIconByFileExt('pdf'));
  try
    Image1.Picture.Icon.LoadFromStream(S);
  finally
    S.Free;
  end;
end;