C++ PathType::rewind方法代码示例

bool middle_point(PathType & path, double & x, double & y)
{
    double x0 = 0;
    double y0 = 0;
    double x1 = 0;
    double y1 = 0;
    double mid_length = 0.5 * path_length(path);
    path.rewind(0);
    unsigned command = path.vertex(&x0,&y0);
    if (command == SEG_END) return false;
    double dist = 0.0;
    while (SEG_END != (command = path.vertex(&x1, &y1)))
    {
        double seg_length = distance(x0, y0, x1, y1);

        if ( dist + seg_length >= mid_length)
        {
            double r = (mid_length - dist)/seg_length;
            x = x0 + (x1 - x0) * r;
            y = y0 + (y1 - y0) * r;
            break;
        }
        dist += seg_length;
        x0 = x1;
        y0 = y1;
    }
    return true;
}

bool hit_test(PathType & path, double x, double y, double tol)
{
    bool inside=false;
    double x0 = 0;
    double y0 = 0;
    double x1 = 0;
    double y1 = 0;
    path.rewind(0);
    unsigned command = path.vertex(&x0, &y0);
    if (command == SEG_END) return false;
    unsigned count = 0;
    while (SEG_END != (command = path.vertex(&x1, &y1)))
    {
        ++count;
        if (command == SEG_MOVETO)
        {
            x0 = x1;
            y0 = y1;
            continue;
        }
        if ((((y1 <= y) && (y < y0)) ||
             ((y0 <= y) && (y < y1))) &&
            (x < (x0 - x1) * (y - y1)/ (y0 - y1) + x1))
            inside=!inside;

        x0 = x1;
        y0 = y1;
    }

    if (count == 0) // one vertex
    {
        return distance(x, y, x0, y0) <= std::fabs(tol);
    }
    return inside;
}

bool hit_test(PathType & path, double x, double y, double tol)
{
    bool inside=false;
    double x0 = 0;
    double y0 = 0;
    double x1 = 0;
    double y1 = 0;
    path.rewind(0);
    unsigned command = path.vertex(&x0, &y0);
    if (command == SEG_END)
    {
        return false;
    }
    unsigned count = 0;
    mapnik::geometry_type::types geom_type = static_cast<mapnik::geometry_type::types>(path.type());
    while (SEG_END != (command = path.vertex(&x1, &y1)))
    {
        if (command == SEG_CLOSE)
        {
            continue;
        }
        ++count;
        if (command == SEG_MOVETO)
        {
            x0 = x1;
            y0 = y1;
            continue;
        }
        switch(geom_type)
        {
        case mapnik::geometry_type::types::Polygon:
        {
            if ((((y1 <= y) && (y < y0)) ||
                 ((y0 <= y) && (y < y1))) &&
                (x < (x0 - x1) * (y - y1)/ (y0 - y1) + x1))
                inside=!inside;
            break;
        }
        case mapnik::geometry_type::types::LineString:
        {
            double distance = point_to_segment_distance(x,y,x0,y0,x1,y1);
            if (distance < tol)
                return true;
            break;
        }
        default:
            break;
        }
        x0 = x1;
        y0 = y1;
    }

    // TODO - handle multi-point?
    if (count == 0) // one vertex
    {
        return distance(x, y, x0, y0) <= tol;
    }
    return inside;
}

bool centroid(PathType & path, double & x, double & y)
{
    double x0 = 0.0;
    double y0 = 0.0;
    double x1 = 0.0;
    double y1 = 0.0;
    double start_x;
    double start_y;

    path.rewind(0);
    unsigned command = path.vertex(&x0, &y0);
    if (command == SEG_END) return false;

    start_x = x0;
    start_y = y0;

    double atmp = 0.0;
    double xtmp = 0.0;
    double ytmp = 0.0;
    unsigned count = 1;
    while (SEG_END != (command = path.vertex(&x1, &y1)))
    {
        if (command == SEG_CLOSE) continue;
        double dx0 = x0 - start_x;
        double dy0 = y0 - start_y;
        double dx1 = x1 - start_x;
        double dy1 = y1 - start_y;

        double ai = dx0 * dy1 - dx1 * dy0;
        atmp += ai;
        xtmp += (dx1 + dx0) * ai;
        ytmp += (dy1 + dy0) * ai;
        x0 = x1;
        y0 = y1;
        ++count;
    }

    if (count <= 2) {
        x = (start_x + x0) * 0.5;
        y = (start_y + y0) * 0.5;
        return true;
    }

    if (atmp != 0)
    {
        x = (xtmp/(3*atmp)) + start_x;
        y = (ytmp/(3*atmp)) + start_y;
    }
    else
    {
        x = x0;
        y = y0;
    }
    return true;
}

double path_length(PathType & path)
{
    double x0 = 0;
    double y0 = 0;
    double x1 = 0;
    double y1 = 0;
    path.rewind(0);
    unsigned command = path.vertex(&x0,&y0);
    if (command == SEG_END) return 0;
    double length = 0;
    while (SEG_END != (command = path.vertex(&x1, &y1)))
    {
        length += distance(x0,y0,x1,y1);
        x0 = x1;
        y0 = y1;
    }
    return length;
}

bool hit_test_first(PathType & path, double x, double y)
{
    bool inside=false;
    double x0 = 0;
    double y0 = 0;
    double x1 = 0;
    double y1 = 0;
    path.rewind(0);
    unsigned command = path.vertex(&x0, &y0);
    if (command == SEG_END)
    {
        return false;
    }
    unsigned count = 0;
    while (SEG_END != (command = path.vertex(&x1, &y1)))
    {
        if (command == SEG_CLOSE)
        {
            break;
        }
        ++count;
        if (command == SEG_MOVETO)
        {
            x0 = x1;
            y0 = y1;
            continue;
        }

        if ((((y1 <= y) && (y < y0)) ||
             ((y0 <= y) && (y < y1))) &&
            (x < (x0 - x1) * (y - y1)/ (y0 - y1) + x1))
            inside=!inside;

        x0 = x1;
        y0 = y1;
    }
    return inside;
}

bool interior_position(PathType & path, double & x, double & y)
{
    // start with the centroid
    if (!label::centroid(path, x,y))
        return false;

    // if we are not a polygon, or the default is within the polygon we are done
    if (hit_test(path,x,y,0.001))
        return true;

    // otherwise we find a horizontal line across the polygon and then return the
    // center of the widest intersection between the polygon and the line.

    std::vector<double> intersections; // only need to store the X as we know the y

    double x0 = 0;
    double y0 = 0;
    path.rewind(0);
    unsigned command = path.vertex(&x0, &y0);
    double x1 = 0;
    double y1 = 0;
    while (SEG_END != (command = path.vertex(&x1, &y1)))
    {
        if (command != SEG_MOVETO)
        {
            // if the segments overlap
            if (y0==y1)
            {
                if (y0==y)
                {
                    double xi = (x0+x1)/2.0;
                    intersections.push_back(xi);
                }
            }
            // if the path segment crosses the bisector
            else if ((y0 <= y && y1 >= y) ||
                     (y0 >= y && y1 <= y))
            {
                // then calculate the intersection
                double xi = x0;
                if (x0 != x1)
                {
                    double m = (y1-y0)/(x1-x0);
                    double c = y0 - m*x0;
                    xi = (y-c)/m;
                }

                intersections.push_back(xi);
            }
        }
        x0 = x1;
        y0 = y1;
    }
    // no intersections we just return the default
    if (intersections.empty())
        return true;
    x0=intersections[0];
    double max_width = 0;
    for (unsigned ii = 1; ii < intersections.size(); ++ii)
    {
        double xi=intersections[ii];
        double xc=(x0+xi)/2.0;
        double width = std::fabs(xi-x0);
        if (width > max_width && hit_test(path,xc,y,0))
        {
            x=xc;
            max_width = width;
            break;
        }
    }
    return true;
}

bool interior_position(PathType & path, double & x, double & y)
{
    // start with the centroid
    if (!label::centroid(path, x,y))
        return false;

    // otherwise we find a horizontal line across the polygon and then return the
    // center of the widest intersection between the polygon and the line.

    std::vector<double> intersections; // only need to store the X as we know the y

    double x0 = 0;
    double y0 = 0;
    path.rewind(0);
    unsigned command = path.vertex(&x0, &y0);
    double x1 = 0;
    double y1 = 0;
    while (SEG_END != (command = path.vertex(&x1, &y1)))
    {
        if (command == SEG_CLOSE)
            continue;
        if (command != SEG_MOVETO)
        {
            // if the segments overlap
            if (y0==y1)
            {
                if (y0==y)
                {
                    double xi = (x0+x1)/2.0;
                    intersections.push_back(xi);
                }
            }
            // if the path segment crosses the bisector
            else if ((y0 <= y && y1 >= y) ||
                     (y0 >= y && y1 <= y))
            {
                // then calculate the intersection
                double xi = x0;
                if (x0 != x1)
                {
                    double m = (y1-y0)/(x1-x0);
                    double c = y0 - m*x0;
                    xi = (y-c)/m;
                }

                intersections.push_back(xi);
            }
        }
        x0 = x1;
        y0 = y1;
    }
    // no intersections we just return the default
    if (intersections.empty())
        return true;
    std::sort(intersections.begin(), intersections.end());
    double max_width = 0;
    for (unsigned ii = 1; ii < intersections.size(); ii += 2)
    {
        double xlow = intersections[ii-1];
        double xhigh = intersections[ii];
        double width = xhigh - xlow;
        if (width > max_width)
        {
            x = (xlow + xhigh) / 2.0;
            max_width = width;
        }
    }
    return true;
}