/usr/include/mapnik/markers_placement.hpp is in libmapnik-dev 2.2.0+ds1-6build2.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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*
* This file is part of Mapnik (c++ mapping toolkit)
*
* Copyright (C) 2011 Artem Pavlenko
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*
*****************************************************************************/
#ifndef MAPNIK_MARKERS_PLACEMENT_HPP
#define MAPNIK_MARKERS_PLACEMENT_HPP
// mapnik
#include <mapnik/ctrans.hpp>
#include <mapnik/debug.hpp>
#include <mapnik/label_collision_detector.hpp>
#include <mapnik/global.hpp> //round
#include <mapnik/box2d.hpp>
#include <mapnik/noncopyable.hpp>
// agg
#include "agg_basics.h"
#include "agg_trans_affine.h"
// stl
#include <cmath>
namespace mapnik {
template <typename Locator, typename Detector>
class markers_placement : mapnik::noncopyable
{
public:
/** Constructor for markers_placement object.
* \param locator Path along which markers are placed (type: vertex source)
* \param size Size of the marker
* \param tr Affine transform
* \param detector Collision detection
* \param spacing Distance between markers. If the value is negative it is
* converted to a positive value with similar magnitude, but
* choosen to optimize marker placement. 0 = no markers
*/
markers_placement(Locator &locator,
box2d<double> const& size,
agg::trans_affine const& tr,
Detector &detector,
double spacing,
double max_error,
bool allow_overlap)
: locator_(locator),
size_(size),
tr_(tr),
detector_(detector),
max_error_(max_error),
allow_overlap_(allow_overlap),
marker_width_((size_ * tr_).width()),
done_(false),
last_x(0.0),
last_y(0.0),
next_x(0.0),
next_y(0.0),
error_(0.0),
spacing_left_(0.0),
marker_nr_(0)
{
if (spacing >= 0)
{
spacing_ = spacing;
}
else if (spacing < 0)
{
spacing_ = find_optimal_spacing(-spacing);
}
rewind();
}
/** Start again at first marker.
* \note Returns the same list of markers only works when they were NOT added
* to the detector.
*/
void rewind()
{
locator_.rewind(0);
//Get first point
done_ = agg::is_stop(locator_.vertex(&next_x, &next_y));
last_x = next_x;
last_y = next_y; // Force request of new segment
error_ = 0.0;
marker_nr_ = 0;
}
/** Get a point where the marker should be placed.
* Each time this function is called a new point is returned.
* \param x Return value for x position
* \param y Return value for x position
* \param angle Return value for rotation angle
* \param add_to_detector Add selected position to detector
* \return True if a place is found, false if none is found.
*/
bool get_point(double & x, double & y, double & angle, bool add_to_detector = true)
{
if (done_)
{
return false;
}
unsigned cmd;
/* This functions starts at the position of the previous marker,
walks along the path, counting how far it has to go in spacing_left.
If one marker can't be placed at the position it should go to it is
moved a bit. The error is compensated for in the next call to this
function.
error > 0: Marker too near to the end of the path.
error = 0: Perfect position.
error < 0: Marker too near to the beginning of the path.
*/
if (marker_nr_ == 0)
{
//First marker
marker_nr_++;
spacing_left_ = spacing_ / 2;
}
else
{
spacing_left_ = spacing_;
}
spacing_left_ -= error_;
error_ = 0.0;
double max_err_allowed = max_error_ * spacing_;
//Loop exits when a position is found or when no more segments are available
while (true)
{
//Do not place markers too close to the beginning of a segment
if (spacing_left_ < marker_width_/2)
{
set_spacing_left(marker_width_/2); //Only moves forward
}
//Error for this marker is too large. Skip to the next position.
if (std::fabs(error_) > max_err_allowed)
{
while (error_ > spacing_)
{
error_ -= spacing_; //Avoid moving backwards
}
spacing_left_ += spacing_ - error_;
error_ = 0.0;
}
double dx = next_x - last_x;
double dy = next_y - last_y;
double segment_length = std::sqrt(dx * dx + dy * dy);
if (segment_length <= spacing_left_)
{
//Segment is too short to place marker. Find next segment
spacing_left_ -= segment_length;
last_x = next_x;
last_y = next_y;
while (agg::is_move_to(cmd = locator_.vertex(&next_x, &next_y)))
{
//Skip over "move" commands
last_x = next_x;
last_y = next_y;
}
if (agg::is_stop(cmd) || cmd == SEG_CLOSE)
{
done_ = true;
return false;
}
continue; //Try again
}
/* At this point we know the following things:
- segment_length > spacing_left
- error is small enough
- at least half a marker fits into this segment
*/
//Check if marker really fits in this segment
if (segment_length < marker_width_)
{
//Segment to short => Skip this segment
set_spacing_left(segment_length + marker_width_/2); //Only moves forward
continue;
}
else if (segment_length - spacing_left_ < marker_width_/2)
{
//Segment is long enough, but we are to close to the end
//Note: This function moves backwards. This could lead to an infinite
// loop when another function adds a positive offset. Therefore we
// only move backwards when there is no offset
if (error_ == 0)
{
set_spacing_left(segment_length - marker_width_/2, true);
}
else
{
//Skip this segment
set_spacing_left(segment_length + marker_width_/2); //Only moves forward
}
continue; //Force checking of max_error constraint
}
angle = std::atan2(dy, dx);
x = last_x + dx * (spacing_left_ / segment_length);
y = last_y + dy * (spacing_left_ / segment_length);
box2d<double> box = perform_transform(angle, x, y);
if (!allow_overlap_ && !detector_.has_placement(box))
{
//10.0 is the approxmiate number of positions tried and choosen arbitrarily
set_spacing_left(spacing_left_ + spacing_ * max_error_ / 10.0); //Only moves forward
continue;
}
if (add_to_detector) detector_.insert(box);
last_x = x;
last_y = y;
return true;
}
}
private:
Locator &locator_;
box2d<double> size_;
agg::trans_affine tr_;
Detector &detector_;
double spacing_;
double max_error_;
bool allow_overlap_;
double marker_width_;
bool done_;
double last_x;
double last_y;
double next_x;
double next_y;
/** If a marker could not be placed at the exact point where it should
* go the next marker's distance will be a bit lower. */
double error_;
double spacing_left_;
unsigned marker_nr_;
/** Rotates the size_ box and translates the position. */
box2d<double> perform_transform(double angle, double dx, double dy)
{
double x1 = size_.minx();
double x2 = size_.maxx();
double y1 = size_.miny();
double y2 = size_.maxy();
agg::trans_affine tr = tr_ * agg::trans_affine_rotation(angle).translate(dx, dy);
double xA = x1, yA = y1, xB = x2, yB = y1, xC = x2, yC = y2, xD = x1, yD = y2;
tr.transform(&xA, &yA);
tr.transform(&xB, &yB);
tr.transform(&xC, &yC);
tr.transform(&xD, &yD);
box2d<double> result(xA, yA, xC, yC);
result.expand_to_include(xB, yB);
result.expand_to_include(xD, yD);
return result;
}
/** Automatically chooses spacing. */
double find_optimal_spacing(double s)
{
rewind();
//Calculate total path length
unsigned cmd = agg::path_cmd_move_to;
double length = 0;
while (!agg::is_stop(cmd))
{
double dx = next_x - last_x;
double dy = next_y - last_y;
length += std::sqrt(dx * dx + dy * dy);
last_x = next_x;
last_y = next_y;
while (agg::is_move_to(cmd = locator_.vertex(&next_x, &next_y)))
{
//Skip over "move" commands
last_x = next_x;
last_y = next_y;
}
}
unsigned points = static_cast<unsigned>(round(length / s));
if (points == 0) return 0.0; //Path to short
return length / points;
}
/** Set spacing_left_, adjusts error_ and performs sanity checks. */
void set_spacing_left(double sl, bool allow_negative=false)
{
double delta_error = sl - spacing_left_;
if (!allow_negative && delta_error < 0)
{
MAPNIK_LOG_WARN(markers_placement) << "Unexpected negative error in markers_placement. Please file a bug report.";
return;
}
#ifdef MAPNIK_DEBUG
if (delta_error == 0.0)
{
MAPNIK_LOG_WARN(markers_placement) << "Not moving at all in set_spacing_left()! Please file a bug report.";
}
#endif
error_ += delta_error;
spacing_left_ = sl;
}
};
}
#endif // MAPNIK_MARKERS_PLACEMENT_HPP
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