500 lines
16 KiB
C++
500 lines
16 KiB
C++
/*****************************************************************************
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*
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* This file is part of Mapnik (c++ mapping toolkit)
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*
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* Copyright (C) 2011 Artem Pavlenko
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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*
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*****************************************************************************/
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#ifndef MAPNIK_HEXTREE_HPP
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#define MAPNIK_HEXTREE_HPP
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// mapnik
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#include <mapnik/global.hpp>
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#include <mapnik/palette.hpp>
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// boost
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#include <boost/utility.hpp>
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#include <boost/unordered_map.hpp>
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// stl
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#include <vector>
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#include <iostream>
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#include <set>
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#include <algorithm>
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#include <cmath>
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namespace mapnik {
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struct RGBAPolicy
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{
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const static unsigned MAX_LEVELS = 6;
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const static unsigned MIN_ALPHA = 5;
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const static unsigned MAX_ALPHA = 250;
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inline static unsigned index_from_level(unsigned level, rgba const& c)
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{
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unsigned shift = 7 - level;
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return (((c.a >> shift) & 1) << 3)
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| (((c.r >> shift) & 1) << 2)
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| (((c.g >> shift) & 1) << 1)
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| ((c.b >> shift) & 1);
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}
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};
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template <typename T, typename InsertPolicy = RGBAPolicy >
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class hextree : private boost::noncopyable
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{
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struct node
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{
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node ()
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: reds(0),
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greens(0),
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blues(0),
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alphas(0),
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count(0),
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pixel_count(0),
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children_count(0)
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{
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memset(&children_[0],0,sizeof(children_));
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}
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~node ()
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{
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for (unsigned i = 0; i < 16; ++i)
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{
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if (children_[i] != 0)
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{
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delete children_[i];
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children_[i]=0;
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}
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}
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}
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bool is_leaf() const
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{
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return (children_count == 0);
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}
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node * children_[16];
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// sum of values for computing mean value using count or pixel_count
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double reds;
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double greens;
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double blues;
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double alphas;
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// if count!=0, then node represents color in output palette
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int count;
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// number of pixels represented by this subtree
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unsigned pixel_count;
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// penalty of using this node as color
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double reduce_cost;
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// number of !=0 positions in children_ array
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byte children_count;
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};
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// highest reduce_cost first
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struct node_rev_cmp
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{
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bool operator() (const node * lhs, const node* rhs) const
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{
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if (lhs->reduce_cost != rhs->reduce_cost)
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{
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return (lhs->reduce_cost > rhs->reduce_cost);
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}
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return (lhs > rhs);
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}
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};
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unsigned max_colors_;
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unsigned colors_;
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// flag indicating existance of invisible pixels (a < InsertPolicy::MIN_ALPHA)
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bool has_holes_;
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node * root_;
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// working palette for quantization, sorted on mean(r,g,b,a) for easier searching NN
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std::vector<rgba> sorted_pal_;
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// index remaping of sorted_pal_ indexes to indexes of returned image palette
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std::vector<unsigned> pal_remap_;
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// rgba hashtable for quantization
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typedef boost::unordered_map<rgba, int, rgba::hash_func> rgba_hash_table;
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mutable rgba_hash_table color_hashmap_;
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// gamma correction to prioritize dark colors (>1.0)
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double gamma_;
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// look up table for gamma correction
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double gammaLUT_[256];
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// transparency handling
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enum transparency_mode_t {NO_TRANSPARENCY=0, BINARY_TRANSPARENCY=1, FULL_TRANSPARENCY=2};
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unsigned trans_mode_;
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inline double gamma(double b, double g) const
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{
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return 255 * std::pow(b/255, g);
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}
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public:
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explicit hextree(unsigned max_colors=256, double g=2.0)
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: max_colors_(max_colors),
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colors_(0),
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has_holes_(false),
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root_(new node()),
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trans_mode_(FULL_TRANSPARENCY)
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{
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setGamma(g);
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}
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~hextree()
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{
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delete root_;
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}
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void setMaxColors(unsigned max_colors)
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{
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max_colors_ = max_colors;
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}
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void setGamma(double g)
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{
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gamma_ = g;
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for (unsigned i=0; i<256; i++)
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{
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gammaLUT_[i] = gamma(i, 1/gamma_);
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}
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}
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void setTransMode(unsigned t)
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{
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trans_mode_ = t;
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}
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transparency_mode_t getTransMode() const
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{
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return trans_mode_;
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}
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// process alpha value based on trans_mode_
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byte preprocessAlpha(byte a) const
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{
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switch(trans_mode_)
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{
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case NO_TRANSPARENCY:
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return 255;
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case BINARY_TRANSPARENCY:
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return a<127?0:255;
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default:
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return a;
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}
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}
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void insert(T const& data)
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{
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byte a = preprocessAlpha(data.a);
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unsigned level = 0;
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node * cur_node = root_;
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if (a < InsertPolicy::MIN_ALPHA)
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{
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has_holes_ = true;
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return;
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}
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while (true)
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{
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cur_node->pixel_count++;
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cur_node->reds += gammaLUT_[data.r];
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cur_node->greens += gammaLUT_[data.g];
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cur_node->blues += gammaLUT_[data.b];
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cur_node->alphas += a;
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if (level == InsertPolicy::MAX_LEVELS)
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{
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if (cur_node->pixel_count == 1)
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{
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++colors_;
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}
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break;
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}
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unsigned idx = InsertPolicy::index_from_level(level,data);
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if (cur_node->children_[idx] == 0)
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{
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cur_node->children_count++;
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cur_node->children_[idx] = new node();
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}
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cur_node = cur_node->children_[idx];
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++level;
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}
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}
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// return color index in returned earlier palette
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int quantize(rgba const& c) const
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{
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byte a = preprocessAlpha(c.a);
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unsigned ind=0;
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if (a < InsertPolicy::MIN_ALPHA || colors_ == 0)
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{
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return 0;
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}
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if (colors_ == 1)
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{
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return pal_remap_[has_holes_?1:0];
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}
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rgba_hash_table::iterator it = color_hashmap_.find(c);
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if (it == color_hashmap_.end())
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{
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int dr, dg, db, da;
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int dist, newdist;
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// find closest match based on mean of r,g,b,a
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std::vector<rgba>::const_iterator pit =
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std::lower_bound(sorted_pal_.begin(), sorted_pal_.end(), c, rgba::mean_sort_cmp());
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ind = pit-sorted_pal_.begin();
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if (ind == sorted_pal_.size())
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ind--;
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dr = sorted_pal_[ind].r - c.r;
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dg = sorted_pal_[ind].g - c.g;
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db = sorted_pal_[ind].b - c.b;
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da = sorted_pal_[ind].a - a;
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dist = dr*dr + dg*dg + db*db + da*da;
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int poz = ind;
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// search neighbour positions in both directions for better match
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for (int i = poz - 1; i >= 0; i--)
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{
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dr = sorted_pal_[i].r - c.r;
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dg = sorted_pal_[i].g - c.g;
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db = sorted_pal_[i].b - c.b;
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da = sorted_pal_[i].a - a;
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// stop criteria based on properties of used sorting
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if (((dr+db+dg+da) * (dr+db+dg+da) / 4 > dist))
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{
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break;
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}
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newdist = dr*dr + dg*dg + db*db + da*da;
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if (newdist < dist)
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{
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ind = i;
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dist = newdist;
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}
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}
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for (unsigned i = poz + 1; i < sorted_pal_.size(); i++)
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{
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dr = sorted_pal_[i].r - c.r;
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dg = sorted_pal_[i].g - c.g;
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db = sorted_pal_[i].b - c.b;
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da = sorted_pal_[i].a - a;
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// stop criteria based on properties of used sorting
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if ((dr+db+dg+da) * (dr+db+dg+da) / 4 > dist)
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{
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break;
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}
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newdist = dr*dr + dg*dg + db*db + da*da;
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if (newdist < dist)
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{
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ind = i;
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dist = newdist;
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}
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}
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//put found index in hash map
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color_hashmap_[c] = ind;
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}
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else
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{
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ind = it->second;
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}
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return pal_remap_[ind];
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}
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void create_palette(std::vector<rgba> & palette)
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{
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sorted_pal_.clear();
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if (has_holes_)
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{
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max_colors_--;
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sorted_pal_.push_back(rgba(0,0,0,0));
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}
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assign_node_colors();
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sorted_pal_.reserve(colors_);
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create_palette_rek(sorted_pal_, root_);
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delete root_;
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root_ = new node();
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// sort palette for binary searching in quantization
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std::sort(sorted_pal_.begin(), sorted_pal_.end(), rgba::mean_sort_cmp());
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// returned palette is rearanged, so that colors with a<255 are at the begining
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pal_remap_.resize(sorted_pal_.size());
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palette.clear();
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palette.reserve(sorted_pal_.size());
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for (unsigned i=0; i<sorted_pal_.size(); i++)
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{
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if (sorted_pal_[i].a<255)
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{
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pal_remap_[i] = palette.size();
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palette.push_back(sorted_pal_[i]);
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}
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}
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for (unsigned i=0; i<sorted_pal_.size(); i++)
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{
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if (sorted_pal_[i].a==255)
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{
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pal_remap_[i] = palette.size();
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palette.push_back(sorted_pal_[i]);
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}
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}
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}
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private:
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void print_tree(node *r, int d=0, int id=0) const
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{
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for (int i=0; i<d; i++)
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{
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printf("\t");
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}
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if (r->count>0)
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{
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printf("%d: (+%d/%d/%.5f) (%d %d %d %d)\n",
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id, (int)r->count, (int)r->pixel_count, r->reduce_cost,
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(int)round(gamma(r->reds / r->count, gamma_)),
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(int)round(gamma(r->greens / r->count, gamma_)),
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(int)round(gamma(r->blues / r->count, gamma_)),
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(int)(r->alphas / r->count));
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}
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else
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{
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printf("%d: (%d/%d/%.5f) (%d %d %d %d)\n", id,
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(int)r->count, (int)r->pixel_count, r->reduce_cost,
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(int)round(gamma(r->reds / r->pixel_count, gamma_)),
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(int)round(gamma(r->greens / r->pixel_count, gamma_)),
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(int)round(gamma(r->blues / r->pixel_count, gamma_)),
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(int)(r->alphas / r->pixel_count));
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}
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for (unsigned idx=0; idx < 16; ++idx)
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{
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if (r->children_[idx] != 0)
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{
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print_tree(r->children_[idx], d+1, idx);
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}
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}
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}
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// traverse tree and search for nodes with count!=0, that represent single color.
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// clip extreme alfa values
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void create_palette_rek(std::vector<rgba> & palette, node * itr) const
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{
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if (itr->count >= 3)
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{
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unsigned count = itr->count;
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byte a = byte(itr->alphas/float(count));
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if (a > InsertPolicy::MAX_ALPHA) a = 255;
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if (a < InsertPolicy::MIN_ALPHA) a = 0;
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palette.push_back(rgba((byte)round(gamma(itr->reds / count, gamma_)),
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(byte)round(gamma(itr->greens / count, gamma_)),
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(byte)round(gamma(itr->blues / count, gamma_)), a));
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}
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for (unsigned idx=0; idx < 16; ++idx)
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{
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if (itr->children_[idx] != 0)
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{
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create_palette_rek(palette, itr->children_[idx]);
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}
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}
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}
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// assign value to r, representing some penalty for assigning one
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// color to all pixels in this subtree
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void compute_cost(node *r)
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{
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//initial small value, so that all nodes have >0 cost
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r->reduce_cost = r->pixel_count/1000.0;
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if (r->children_count==0)
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{
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return;
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}
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// mean color of all pixels in subtree
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double mean_r = r->reds / r->pixel_count;
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double mean_g = r->greens / r->pixel_count;
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double mean_b = r->blues / r->pixel_count;
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double mean_a = r->alphas / r->pixel_count;
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for (unsigned idx=0; idx < 16; ++idx)
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{
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if (r->children_[idx] != 0)
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{
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double dr,dg,db,da;
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compute_cost(r->children_[idx]);
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// include childrens penalty
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r->reduce_cost += r->children_[idx]->reduce_cost;
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// difference between mean value and subtree mean value
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dr = r->children_[idx]->reds / r->children_[idx]->pixel_count - mean_r;
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dg = r->children_[idx]->greens / r->children_[idx]->pixel_count - mean_g;
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db = r->children_[idx]->blues / r->children_[idx]->pixel_count - mean_b;
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da = r->children_[idx]->alphas / r->children_[idx]->pixel_count - mean_a;
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// penalty_x = d_x^2 * pixel_count * mean_alfa/255, where x=r,g,b,a
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// mean_alpha/255 because more opaque color = more noticable differences
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r->reduce_cost += (dr*dr + dg*dg + db*db + da*da) * r->children_[idx]->alphas / 255;
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}
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}
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}
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// starting from root_, unfold nodes with biggest penalty
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// until all available colors are assigned to processed nodes
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void assign_node_colors()
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{
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compute_cost(root_);
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int tries = 0;
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// at the begining, single color assigned to root_
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colors_ = 1;
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root_->count = root_->pixel_count;
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std::set<node*,node_rev_cmp> colored_leaves_heap;
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colored_leaves_heap.insert(root_);
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while((!colored_leaves_heap.empty() && (colors_ < max_colors_) && (tries < 16)))
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{
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// select worst node to remove it from palette and replace with children
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node * cur_node = *colored_leaves_heap.begin();
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colored_leaves_heap.erase(colored_leaves_heap.begin());
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if (((cur_node->children_count + colors_ - 1) > max_colors_))
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{
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tries++;
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continue; // try few times, maybe next will have less children
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}
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tries = 0;
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// ignore leaves and also nodes with small mean error and not excessive number of pixels
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if (cur_node->pixel_count > 0 &&
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(cur_node->children_count > 0) &&
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(((cur_node->reduce_cost / cur_node->pixel_count + 1) * std::log(double(cur_node->pixel_count))) > 15)
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)
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{
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colors_--;
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cur_node->count = 0;
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for (unsigned idx=0; idx < 16; ++idx)
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{
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if (cur_node->children_[idx] != 0)
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{
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node *n = cur_node->children_[idx];
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n->count = n->pixel_count;
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colored_leaves_heap.insert(n);
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colors_++;
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}
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}
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}
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}
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}
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};
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} // namespace mapnik
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#endif // MAPNIK_HEXTREE_HPP
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