static void walk(Chaincode *cc, int start_node, unsigned char **pixels, int dx, int dy)
{
int x, y;
int allocated = 20;
int count = 0;
Rope *rope;
char *steps;
assert(0 <= start_node && start_node < cc->node_count);
x = cc->nodes[start_node].x;
y = cc->nodes[start_node].y;
/* Check that there's indeed a road in the given direction. */
if (!pixels[y + dy][x + dx])
return;
/* Check that we haven't passed here before. */
if (passed_edge(pixels[y][x], dx, dy))
return;
cc->nodes[start_node].rope_indices[count_passed_edges(pixels[y][x])] = cc->rope_count;
steps = MALLOC(char, allocated);
mark_edge(pixels, x, y, dx, dy);
x += dx;
y += dy;
*append_step(&steps, &count, &allocated) = chaincode_char(dx, dy);
if (pixels[y][x] == 1)
{
pixels[y][x] = 0;
determine_direction_first_time(pixels, x, y, &dx, &dy);
while (1)
{
x += dx;
y += dy;
*append_step(&steps, &count, &allocated) = chaincode_char(dx, dy);
if (pixels[y][x] != 1) break;
pixels[y][x] = 0;
determine_direction(pixels, x, y, &dx, &dy);
}
}
/* We've arrived at a hot point. Mark the entrance. */
assert(!passed_edge(pixels[y][x], -dx, -dy));
mark_edge(pixels, x, y, -dx, -dy);
/* Add the rope. */
rope = chaincode_append_rope(cc);
rope->start = start_node;
rope->end = find_node(cc, x, y);
rope->steps = REALLOC(char, steps, count);
rope->length = count;
cc->nodes[rope->end].rope_indices[count_passed_edges(pixels[y][x]) - 1] = cc->rope_count - 1;
}
static pixel_outline_type
find_one_outline (edge_type original_edge,
unsigned original_row, unsigned original_col,
bitmap_type *marked)
{
pixel_outline_type outline = new_pixel_outline ();
unsigned row = original_row, col = original_col;
edge_type edge = original_edge;
do
{
/* Put this edge on to the output list, changing to Cartesian, and
taking account of the side bearings. */
append_coordinate (&outline, col,
sel_get_height() - row, edge);
mark_edge (edge, row, col, marked);
next_outline_edge (&edge, &row, &col);
}
while (row != original_row || col != original_col || edge != original_edge);
return outline;
}