DIRECTION_HORIZONTAL  182 libavfilter/vf_edgedetect.c         if (gy > -tanpi8gx  && gy <  tanpi8gx)  return DIRECTION_HORIZONTAL;
DIRECTION_HORIZONTAL  236 libavfilter/vf_edgedetect.c             case DIRECTION_HORIZONTAL:  COPY_MAXIMA( 0, -1,  0,  1); break;