#ifndef UNSUPPORTED
static void
do_stereogram(void *data, struct taskinfo *task, int r1, int r2)
{
    struct filter *f = (struct filter *) data;
    int i, y, lc;
    struct stereogramdata *s = (struct stereogramdata *) f->data;
    register cpixel_t *cs, *c, *src, *src1, *ce;
    register spixel_t *c1;
    unsigned int *pixels = f->image->palette->pixels;
    s->minc = NCOLORS;
    for (i = r1; i < r2; i++) {
	int i1;
	for (i1 = 0; i1 < 2; i1++) {
	    c1 = (spixel_t *) f->childimage->currlines[i];
	    c = cs = (cpixel_t *) f->image->currlines[2 * i + i1];
	    ce = p_add(cs, f->image->width);
	    src = src1 = c;
	    lc = 1024;
	    while (c < ce) {
		y = *c1;
		if (y == lc)
		    p_inc(src, 2);
		else {
		    lc = y;
		    if (y < s->minc && y != 0)
			s->minc = y;
		    y = table[y];
		    src = p_add(c, -y);
		}
		if (src < src1) {
		    p_set(c, pixels[(rand() & 15)]);
		    p_setp(c, 1, pixels[(rand() & 15)]);
		} else {
		    if (src <= cs) {
			p_set(c, pixels[(rand() & 15)]);
			p_setp(c, 1, pixels[(rand() & 15)]);
		    } else {
			p_copy(c, 0, src, 0);
			p_copy(c, 1, src, 1);
		    }
		    src1 = src;
		}
		p_inc(c, 2);
		c1++;
	    }
	}
    }
}
#endif
#undef do_stereogram