#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]) + 1;
	else
	    up = ((spixel_t *) f->childimage->currlines[y]) + 1;

	if (y != f->image->height - 1)
	    down = ((spixel_t *) f->childimage->currlines[y + 1]) + 1;
	else
	    down = ((spixel_t *) f->childimage->currlines[y]) + 1;

	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[0] > up[0] || input[0] > down[0]) {
		p_set(output, pixels[input[0]]);
	    } else if (input[0] != input[1]) {
		if (input[0] < input[1]) {
		    p_set(output, black);
		    p_inc(output, 1);
		    input++;
		    up++;
		    down++;
		}
		p_set(output, pixels[input[0]]);
	    } else
		p_set(output, black);
	    p_inc(output, 1);
	    input++;
	    up++;
	    down++;
	}
    }
}
#endif
#undef do_edge