#ifndef UNSUPPORTED
static void do_edge(void *data, struct taskinfo *task, int r1, int r2)
{
    struct filter *f = (struct filter *) data;
    int y;
    unsigned int *pixels = f->image->palette->pixels;
    register unsigned int black = f->image->palette->pixels[0];
    register cpixel_t *output, *end;
    register spixel_t *up, *down, *input;
    for (y = r1; y < r2; y++) {
	output = p_add(((cpixel_t *) f->image->currlines[y]), 1);
	input = ((spixel_t *) f->childimage->currlines[y]) + 1;
	if (y != 0)
	    up = ((spixel_t *) f->childimage->currlines[y - 1]) + 2;
	else
	    up = ((spixel_t *) f->childimage->currlines[y]) + 2;
	if (y != f->image->height - 1)
	    down = ((spixel_t *) f->childimage->currlines[y + 1]) + 2;
	else
	    down = ((spixel_t *) f->childimage->currlines[y]) + 2;
	end =
	    p_add(((cpixel_t *) f->image->currlines[y]),
		  f->image->width - 1);
	p_setp(output, -1, 0);
	p_setp(output, f->image->width - 2, 0);
	while (output < end) {
	    if (input[1] != input[0] || input[0] != up[0]
		|| input[0] != down[0]) {
		if (output < end - 2) {
		    p_set(output, pixels[input[0]]);
		    p_setp(output, 1, pixels[input[1]]);
		    p_setp(output, 2, pixels[input[2]]);
		    p_inc(output, 3);
		    input += 3;
		    up += 3;
		    down += 3;
		    while (output < end - 1
			   && (input[0] != up[-1] || input[0] != down[-1]))
		    {
			p_set(output, pixels[input[0]]);
			p_setp(output, 1, pixels[input[1]]);
			p_inc(output, 2);
			input += 2;
			up += 2;
			down += 2;
		    }
		    if (output < end
			&& (input[-1] != input[0] || up[-2] != input[0]
			    || down[-2] != input[0])) {
			p_set(output, pixels[input[0]]);
			p_inc(output, 1);
			input++;
			up++;
			down++;
		    }
		} else
		    p_set(output, pixels[*input]), p_inc(output, 1),
			input++, up++, down++;
	    } else
		p_set(output, black), p_inc(output, 1), input++, up++,
		    down++;
	}
    }
}
#endif
#undef do_edge