This is one of my plugins for ArtEffect2/3+.

HighPass is a technical filter.
Low frequencies are filtered out. Low frequencies in pictures are areas of
the same color/not much colors/not much contrast.

 PERMSSN    UID  GID    PACKED    SIZE  RATIO     CRC       STAMP          NAME
---------- ----------- ------- ------- ------ ---------- ------------ -------------
[generic]                 2760    7027  39.3% -lh5- 36a0 Jul 23  1999 HighPass.guide
[generic]                10600   17508  60.5% -lh5- 1b6e Jul 23  1999 plugins2/HighPass.p2m
[generic]                10946   18820  58.2% -lh5- acca Jul 23  1999 plugins2/HighPass.p2n
[generic]                10593   17504  60.5% -lh5- 7a57 Jul 23  1999 plugins2/HighPass.p4s
---------- ----------- ------- ------- ------ ---------- ------------ -------------
 Total         4 files   34899   60859  57.3%            Jul 25  1999