mapnik/src/raster_colorizer.cpp

/*****************************************************************************
 *
 * 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
 *
 *****************************************************************************/

// mapnik
#include <mapnik/debug.hpp>
#include <mapnik/value_types.hpp>
#include <mapnik/value.hpp> // for to_double
#include <mapnik/feature.hpp>
#include <mapnik/raster.hpp>
#include <mapnik/raster_colorizer.hpp>
#include <mapnik/enumeration.hpp>

// stl
#include <limits>
#include <cmath>

namespace mapnik
{

//! \brief Strings for the colorizer_mode enumeration
static const char *colorizer_mode_strings[] = {
    "inherit",
    "linear",
    "discrete",
    "exact",
    ""
};

IMPLEMENT_ENUM( colorizer_mode, colorizer_mode_strings )


colorizer_stop::colorizer_stop(float value, colorizer_mode mode,
                               color const& _color,
                               std::string const& label)
: value_(value)
    , mode_(mode)
    , color_(_color)
    , label_(label)
{

}

colorizer_stop::colorizer_stop(colorizer_stop const& stop)
    : value_(stop.value_)
    , mode_(stop.mode_)
    , color_(stop.color_)
    , label_(stop.label_)
{
}


colorizer_stop::~colorizer_stop()
{

}


bool colorizer_stop::operator==(colorizer_stop const& other) const
{
    return  (value_ == other.value_) &&
        (color_ == other.color_) &&
        (mode_ == other.mode_) &&
        (label_ == other.label_);
}


std::string colorizer_stop::to_string() const
{
    std::stringstream ss;
    ss << color_.to_string() << " " << value_ << " " << mode_.as_string();
    return ss.str();
}





raster_colorizer::raster_colorizer(colorizer_mode mode, color const& _color)
    : default_mode_(mode)
    , default_color_(_color)
    , epsilon_(std::numeric_limits<float>::epsilon())
{

}

raster_colorizer::~raster_colorizer()
{
}

bool raster_colorizer::add_stop(colorizer_stop const& stop)
{
    //make sure stops are added in order of value
    if(stops_.size())
    {
        if(stop.get_value() <= stops_.back().get_value())
        {
            return false;
        }
    }

    stops_.push_back(stop);

    return true;
}

void raster_colorizer::colorize(raster_ptr const& raster, feature_impl const& f) const
{
    unsigned *imageData = raster->data_.getData();

    int len = raster->data_.width() * raster->data_.height();
    boost::optional<double> const& nodata = raster->nodata();
    for (int i=0; i<len; ++i)
    {
        // the GDAL plugin reads single bands as floats
        float value = *reinterpret_cast<float *> (&imageData[i]);
        if (nodata && (std::fabs(value - *nodata) < epsilon_))
        {
            imageData[i] = 0;
        }
        else
        {
            imageData[i] = get_color(value);
        }
    }
}

inline unsigned interpolate(unsigned start, unsigned end, float fraction)
{
    return static_cast<unsigned>(fraction * ((float)end - (float)start) + start);
}

unsigned raster_colorizer::get_color(float value) const
{
    int stopCount = stops_.size();

    //use default color if no stops
    if(stopCount == 0)
    {
        return default_color_.rgba();
    }

    //1 - Find the stop that the value is in
    int stopIdx = -1;
    bool foundStopIdx = false;

    for(int i=0; i<stopCount; ++i)
    {
        if(value < stops_[i].get_value())
        {
            stopIdx = i-1;
            foundStopIdx = true;
            break;
        }
    }

    if(!foundStopIdx)
    {
        stopIdx = stopCount-1;
    }

    //2 - Find the next stop
    int nextStopIdx = stopIdx + 1;
    if(nextStopIdx >= stopCount)
    {
        //there is no next stop
        nextStopIdx = stopCount - 1;
    }

    //3 - Work out the mode
    colorizer_mode stopMode;
    if( stopIdx == -1 )
    {
        //before the first stop
        stopMode = default_mode_;
    }
    else
    {
        stopMode = stops_[stopIdx].get_mode();
        if(stopMode == COLORIZER_INHERIT)
        {
            stopMode = default_mode_;
        }
    }

    //4 - Calculate the colour
    color stopColor;
    color nextStopColor;
    float stopValue = 0;
    float nextStopValue = 0;
    color outputColor = get_default_color();
    if(stopIdx == -1)
    {
        stopColor = default_color_;
        nextStopColor = stops_[nextStopIdx].get_color();
        stopValue = value;
        nextStopValue = stops_[nextStopIdx].get_value();
    }
    else
    {
        stopColor = stops_[stopIdx].get_color();
        nextStopColor = stops_[nextStopIdx].get_color();
        stopValue = stops_[stopIdx].get_value();
        nextStopValue = stops_[nextStopIdx].get_value();
    }

    switch(stopMode)
    {
    case COLORIZER_LINEAR:
    {
        //deal with this separately so we don't have to worry about div0
        if(nextStopValue == stopValue)
        {
            outputColor = stopColor;
        }
        else
        {
            float fraction = (value - stopValue) / (nextStopValue - stopValue);

            unsigned r = interpolate(stopColor.red(), nextStopColor.red(),fraction);
            unsigned g = interpolate(stopColor.green(), nextStopColor.green(),fraction);
            unsigned b = interpolate(stopColor.blue(), nextStopColor.blue(),fraction);
            unsigned a = interpolate(stopColor.alpha(), nextStopColor.alpha(),fraction);

            outputColor.set_red(r);
            outputColor.set_green(g);
            outputColor.set_blue(b);
            outputColor.set_alpha(a);
        }

    }
    break;
    case COLORIZER_DISCRETE:
        outputColor = stopColor;
        break;
    case COLORIZER_EXACT:
    default:
        //approximately equal (within epsilon)
        if(std::fabs(value - stopValue) < epsilon_)
        {
            outputColor = stopColor;
        }
        else
        {
            outputColor = default_color_;
        }
        break;
    }


    /*
      MAPNIK_LOG_DEBUG(raster_colorizer) << "raster_colorizer: get_color " << value;
      MAPNIK_LOG_DEBUG(raster_colorizer) << "\tstopIdx: " << stopIdx;
      MAPNIK_LOG_DEBUG(raster_colorizer) << "\tnextStopIdx: " << nextStopIdx;
      MAPNIK_LOG_DEBUG(raster_colorizer) << "\tstopValue: " << stopValue;
      MAPNIK_LOG_DEBUG(raster_colorizer) << "\tnextStopValue: " << nextStopValue;
      MAPNIK_LOG_DEBUG(raster_colorizer) << "\tstopColor: " << stopColor.to_string();
      MAPNIK_LOG_DEBUG(raster_colorizer) << "\tnextStopColor: " << nextStopColor.to_string();
      MAPNIK_LOG_DEBUG(raster_colorizer) << "\tstopMode: " << stopMode.as_string();
      MAPNIK_LOG_DEBUG(raster_colorizer) << "\toutputColor: " << outputColor.to_string();
    */

    return outputColor.rgba();
}


}