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mapnik/include/mapnik/hextree.hpp

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/*****************************************************************************
*
* This file is part of Mapnik (c++ mapping toolkit)
*
* Copyright (C) 2014 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_HEXTREE_HPP
#define MAPNIK_HEXTREE_HPP
// mapnik
#include <mapnik/global.hpp>
#include <mapnik/palette.hpp>
#include <mapnik/util/noncopyable.hpp>
// stl
#include <algorithm>
#include <vector>
#include <set>
#include <cmath>
namespace mapnik {
struct RGBAPolicy
{
const static unsigned MAX_LEVELS = 6;
const static unsigned MIN_ALPHA = 5;
const static unsigned MAX_ALPHA = 250;
inline static unsigned index_from_level(unsigned level, rgba const& c)
{
unsigned shift = 7 - level;
return (((c.a >> shift) & 1) << 3)
| (((c.r >> shift) & 1) << 2)
| (((c.g >> shift) & 1) << 1)
| ((c.b >> shift) & 1);
}
};
template <typename T, typename InsertPolicy = RGBAPolicy >
class hextree : private util::noncopyable
{
struct node
{
node ()
: reds(0.0),
greens(0.0),
blues(0.0),
alphas(0.0),
count(0),
pixel_count(0),
reduce_cost(0.0),
children_count(0)
{
std::fill(children_, children_ + 16, nullptr);
}
~node ()
{
for (unsigned i = 0; i < 16; ++i)
{
if (children_[i] != 0)
{
delete children_[i];
children_[i]=0;
}
}
}
bool is_leaf() const
{
return (children_count == 0);
}
node * children_[16];
// sum of values for computing mean value using count or pixel_count
double reds;
double greens;
double blues;
double alphas;
// if count!=0, then node represents color in output palette
int count;
// number of pixels represented by this subtree
unsigned pixel_count;
// penalty of using this node as color
double reduce_cost;
// number of !=0 positions in children_ array
std::uint8_t children_count;
};
// highest reduce_cost first
struct node_rev_cmp
{
bool operator() (const node * lhs, const node* rhs) const
{
if (lhs->reduce_cost != rhs->reduce_cost)
{
return (lhs->reduce_cost > rhs->reduce_cost);
}
return (lhs > rhs);
}
};
unsigned max_colors_;
unsigned colors_;
// flag indicating existance of invisible pixels (a < InsertPolicy::MIN_ALPHA)
bool has_holes_;
const std::unique_ptr<node> root_;
// working palette for quantization, sorted on mean(r,g,b,a) for easier searching NN
std::vector<rgba> sorted_pal_;
// index remaping of sorted_pal_ indexes to indexes of returned image palette
std::vector<unsigned> pal_remap_;
// rgba hashtable for quantization
mutable rgba_hash_table color_hashmap_;
// gamma correction to prioritize dark colors (>1.0)
double gamma_;
// look up table for gamma correction
double gammaLUT_[256];
// transparency handling
enum transparency_mode_t {NO_TRANSPARENCY=0, BINARY_TRANSPARENCY=1, FULL_TRANSPARENCY=2};
unsigned trans_mode_;
inline double gamma(double b, double g) const
{
return 255 * std::pow(b/255, g);
}
public:
explicit hextree(unsigned max_colors=256, double g=2.0)
: max_colors_(max_colors),
colors_(0),
has_holes_(false),
root_(new node()),
#ifdef USE_DENSE_HASH_MAP
// TODO - test for any benefit to initializing at a larger size
color_hashmap_(),
#endif
trans_mode_(FULL_TRANSPARENCY)
{
setGamma(g);
#ifdef USE_DENSE_HASH_MAP
color_hashmap_.set_empty_key(0);
#endif
}
~hextree()
{}
void setMaxColors(unsigned max_colors)
{
max_colors_ = max_colors;
}
void setGamma(double g)
{
gamma_ = g;
for (unsigned i=0; i<256; i++)
{
gammaLUT_[i] = gamma(i, 1/gamma_);
}
}
void setTransMode(unsigned t)
{
trans_mode_ = t;
}
transparency_mode_t getTransMode() const
{
return trans_mode_;
}
// process alpha value based on trans_mode_
std::uint8_t preprocessAlpha(std::uint8_t a) const
{
switch(trans_mode_)
{
case NO_TRANSPARENCY:
return 255;
case BINARY_TRANSPARENCY:
return a<127?0:255;
default:
return a;
}
}
void insert(T const& data)
{
std::uint8_t a = preprocessAlpha(data.a);
unsigned level = 0;
node * cur_node = root_.get();
if (a < InsertPolicy::MIN_ALPHA)
{
has_holes_ = true;
return;
}
while (true)
{
cur_node->pixel_count++;
cur_node->reds += gammaLUT_[data.r];
cur_node->greens += gammaLUT_[data.g];
cur_node->blues += gammaLUT_[data.b];
cur_node->alphas += a;
if (level == InsertPolicy::MAX_LEVELS)
{
if (cur_node->pixel_count == 1)
{
++colors_;
}
break;
}
unsigned idx = InsertPolicy::index_from_level(level,data);
if (cur_node->children_[idx] == 0)
{
cur_node->children_count++;
cur_node->children_[idx] = new node();
}
cur_node = cur_node->children_[idx];
++level;
}
}
// return color index in returned earlier palette
int quantize(unsigned val) const
{
std::uint8_t a = preprocessAlpha(U2ALPHA(val));
unsigned ind=0;
if (a < InsertPolicy::MIN_ALPHA || colors_ == 0)
{
return 0;
}
if (colors_ == 1)
{
return pal_remap_[has_holes_?1:0];
}
rgba_hash_table::iterator it = color_hashmap_.find(val);
if (it == color_hashmap_.end())
{
rgba c(val);
int dr, dg, db, da;
int dist, newdist;
// find closest match based on mean of r,g,b,a
std::vector<rgba>::const_iterator pit =
std::lower_bound(sorted_pal_.begin(),sorted_pal_.end(), c, rgba::mean_sort_cmp());
ind = pit-sorted_pal_.begin();
if (ind == sorted_pal_.size())
ind--;
dr = sorted_pal_[ind].r - c.r;
dg = sorted_pal_[ind].g - c.g;
db = sorted_pal_[ind].b - c.b;
da = sorted_pal_[ind].a - a;
dist = dr*dr + dg*dg + db*db + da*da;
int poz = ind;
// search neighbour positions in both directions for better match
for (int i = poz - 1; i >= 0; i--)
{
dr = sorted_pal_[i].r - c.r;
dg = sorted_pal_[i].g - c.g;
db = sorted_pal_[i].b - c.b;
da = sorted_pal_[i].a - a;
// stop criteria based on properties of used sorting
if (((dr+db+dg+da) * (dr+db+dg+da) / 4 > dist))
{
break;
}
newdist = dr*dr + dg*dg + db*db + da*da;
if (newdist < dist)
{
ind = i;
dist = newdist;
}
}
for (unsigned i = poz + 1; i < sorted_pal_.size(); i++)
{
dr = sorted_pal_[i].r - c.r;
dg = sorted_pal_[i].g - c.g;
db = sorted_pal_[i].b - c.b;
da = sorted_pal_[i].a - a;
// stop criteria based on properties of used sorting
if ((dr+db+dg+da) * (dr+db+dg+da) / 4 > dist)
{
break;
}
newdist = dr*dr + dg*dg + db*db + da*da;
if (newdist < dist)
{
ind = i;
dist = newdist;
}
}
//put found index in hash map
color_hashmap_[val] = ind;
}
else
{
ind = it->second;
}
return pal_remap_[ind];
}
void create_palette(std::vector<rgba> & palette)
{
sorted_pal_.clear();
if (has_holes_)
{
max_colors_--;
sorted_pal_.push_back(rgba(0,0,0,0));
}
assign_node_colors();
sorted_pal_.reserve(colors_);
create_palette_rek(sorted_pal_, root_.get());
// sort palette for binary searching in quantization
std::sort(sorted_pal_.begin(), sorted_pal_.end(), rgba::mean_sort_cmp());
// returned palette is rearanged, so that colors with a<255 are at the begining
pal_remap_.resize(sorted_pal_.size());
palette.clear();
palette.reserve(sorted_pal_.size());
for (unsigned i=0; i<sorted_pal_.size(); ++i)
{
if (sorted_pal_[i].a<255)
{
pal_remap_[i] = static_cast<unsigned>(palette.size());
palette.push_back(sorted_pal_[i]);
}
}
for (unsigned i=0; i<sorted_pal_.size(); ++i)
{
if (sorted_pal_[i].a==255)
{
pal_remap_[i] = static_cast<unsigned>(palette.size());
palette.push_back(sorted_pal_[i]);
}
}
}
private:
void print_tree(node *r, int d=0, int id=0) const
{
for (int i=0; i<d; i++)
{
printf("\t");
}
if (r->count>0)
{
printf("%d: (+%d/%d/%.5f) (%d %d %d %d)\n",
id, (int)r->count, (int)r->pixel_count, r->reduce_cost,
(int)round(gamma(r->reds / r->count, gamma_)),
(int)round(gamma(r->greens / r->count, gamma_)),
(int)round(gamma(r->blues / r->count, gamma_)),
(int)(r->alphas / r->count));
}
else
{
printf("%d: (%d/%d/%.5f) (%d %d %d %d)\n", id,
(int)r->count, (int)r->pixel_count, r->reduce_cost,
(int)round(gamma(r->reds / r->pixel_count, gamma_)),
(int)round(gamma(r->greens / r->pixel_count, gamma_)),
(int)round(gamma(r->blues / r->pixel_count, gamma_)),
(int)(r->alphas / r->pixel_count));
}
for (unsigned idx=0; idx < 16; ++idx)
{
if (r->children_[idx] != 0)
{
print_tree(r->children_[idx], d+1, idx);
}
}
}
// traverse tree and search for nodes with count!=0, that represent single color.
// clip extreme alfa values
void create_palette_rek(std::vector<rgba> & palette, node * itr) const
{
if (itr->count != 0)
{
unsigned count = itr->count;
std::uint8_t a = std::uint8_t(itr->alphas/float(count));
if (a > InsertPolicy::MAX_ALPHA) a = 255;
if (a < InsertPolicy::MIN_ALPHA) a = 0;
palette.push_back(rgba((std::uint8_t)round(gamma(itr->reds / count, gamma_)),
(std::uint8_t)round(gamma(itr->greens / count, gamma_)),
(std::uint8_t)round(gamma(itr->blues / count, gamma_)), a));
}
for (unsigned idx=0; idx < 16; ++idx)
{
if (itr->children_[idx] != 0)
{
create_palette_rek(palette, itr->children_[idx]);
}
}
}
// assign value to r, representing some penalty for assigning one
// color to all pixels in this subtree
void compute_cost(node *r)
{
//initial small value, so that all nodes have >0 cost
r->reduce_cost = r->pixel_count/1000.0;
if (r->children_count==0)
{
return;
}
// mean color of all pixels in subtree
double mean_r = r->reds / r->pixel_count;
double mean_g = r->greens / r->pixel_count;
double mean_b = r->blues / r->pixel_count;
double mean_a = r->alphas / r->pixel_count;
for (unsigned idx=0; idx < 16; ++idx)
{
if (r->children_[idx] != 0)
{
double dr,dg,db,da;
compute_cost(r->children_[idx]);
// include childrens penalty
r->reduce_cost += r->children_[idx]->reduce_cost;
// difference between mean value and subtree mean value
dr = r->children_[idx]->reds / r->children_[idx]->pixel_count - mean_r;
dg = r->children_[idx]->greens / r->children_[idx]->pixel_count - mean_g;
db = r->children_[idx]->blues / r->children_[idx]->pixel_count - mean_b;
da = r->children_[idx]->alphas / r->children_[idx]->pixel_count - mean_a;
// penalty_x = d_x^2 * pixel_count * mean_alfa/255, where x=r,g,b,a
// mean_alpha/255 because more opaque color = more noticable differences
r->reduce_cost += (dr*dr + dg*dg + db*db + da*da) * r->children_[idx]->alphas / 255;
}
}
}
// starting from root_, unfold nodes with biggest penalty
// until all available colors are assigned to processed nodes
void assign_node_colors()
{
compute_cost(root_.get());
int tries = 0;
// at the begining, single color assigned to root_
colors_ = 1;
root_->count = root_->pixel_count;
std::set<node*,node_rev_cmp> colored_leaves_heap;
colored_leaves_heap.insert(root_.get());
while((!colored_leaves_heap.empty() && (colors_ < max_colors_) && (tries < 16)))
{
// select worst node to remove it from palette and replace with children
node * cur_node = *colored_leaves_heap.begin();
colored_leaves_heap.erase(colored_leaves_heap.begin());
if (((cur_node->children_count + colors_ - 1) > max_colors_))
{
tries++;
continue; // try few times, maybe next will have less children
}
tries = 0;
// ignore leaves and also nodes with small mean error and not excessive number of pixels
if (cur_node->pixel_count > 0 &&
(cur_node->children_count > 0) &&
(((cur_node->reduce_cost / cur_node->pixel_count + 1) * std::log(double(cur_node->pixel_count))) > 15)
)
{
colors_--;
cur_node->count = 0;
for (unsigned idx=0; idx < 16; ++idx)
{
if (cur_node->children_[idx] != 0)
{
node *n = cur_node->children_[idx];
n->count = n->pixel_count;
colored_leaves_heap.insert(n);
colors_++;
}
}
}
}
}
};
} // namespace mapnik
#endif // MAPNIK_HEXTREE_HPP
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