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;
}
/* Same, but we might have a black pixel where we came from. */
static void determine_direction_first_time(unsigned char **pixels, int x, int y, int *pdx, int *pdy)
{
unsigned char save_pixel = pixels[y - *pdy][x - *pdx];
int new_dx, new_dy;
pixels[y - *pdy][x - *pdx] = 0; /* reduce the task to previous */
determine_direction(pixels, x, y, &new_dx, &new_dy);
pixels[y - *pdy][x - *pdx] = save_pixel;
*pdx = new_dx;
*pdy = new_dy;
}
int main(int argc, char **argv) {
int column = 1;
int row = 1;
int direction = 66;
printf("Begining tests of determine_direction\n");
direction = determine_direction(column,row,column+1,row);
assert(direction == right);
direction = determine_direction(column,row,column-1,row);
assert(direction == left);
direction = determine_direction(column,row,column,row-1);
assert(direction == up);
direction = determine_direction(column,row,column,row+1);
assert(direction == down);
direction = determine_direction(column,row,column+2,row);
assert(direction == invalid);
printf("All tests done\n");
}
Vector::Vector(double x1, double y1, double x2, double y2)
{
x_component_ = std::abs(x2 - x1);
y_component_ = std::abs(y2 - y1);
int quadrant = determine_quadrant(x1, y1, x2, y2);
magnitude_ = sqrt(pow(x_component_, 2) + pow(y_component_, 2));
double theta = radians_to_degrees(acos(x_component_ / magnitude_));
direction_ = determine_direction(quadrant, theta);
set_component_signs(direction_);
Logger::write(Logger::string_stream << "creating vector:");
Logger::write(Logger::string_stream << "\t\tmagnitude: " << magnitude_);
Logger::write(Logger::string_stream << "\t\tdirection: " << direction_);
Logger::write(Logger::string_stream << "\t\tx_component: " << x_component_);
Logger::write(Logger::string_stream << "\t\ty_component: " << y_component_);
Logger::write(Logger::string_stream << "\t\tquadrant: " << quadrant);
Logger::write(Logger::string_stream << "\t\t(" << x1 << "," << y1 << ") & (" << x2 << "," << y2 << ")");
}