Colored Terrain

#include <SFML/Graphics.hpp>
#include <noise/interp.h>
#include <noise/noise.h>
#include <algorithm>
#include <iostream>

#include "ColorScale.h"

namespace sf
{
    typedef Vector2< double > Vector2d;
}

const int SIZE = 256;
const int GRADIENT = 128;

void GetGradient( sf::Image& gradient, int height )
{
    ColorScale scale;
    scale.insert( -1.00, sf::Color(   0,   4,  64 ) ); // Deep water
    scale.insert( -0.60, sf::Color(   0,   8, 128 ) ); // Normal water
    scale.insert( -0.15, sf::Color(   0,  13, 217 ) ); // Shallow water
    scale.insert(  0.05, sf::Color( 253, 255, 209 ) ); // Shore
    scale.insert(  0.25, sf::Color(   0, 145,   7 ) ); // Grass
    scale.insert(  0.45, sf::Color(   0,  77,   4 ) ); // Trees
    scale.insert(  0.65, sf::Color( 100, 100, 100 ) ); // Stone
    scale.insert(  1.00, sf::Color( 255, 255, 255 ) ); // Snow

    gradient.Create( 1, height );
    scale.draw( gradient, sf::Vector2f( 0.f, 0.f ), sf::Vector2f( 0.f, height ), GradientStyle::Linear );
}

sf::Color GetColor( const sf::Image& gradient, double factor )
{
    unsigned int y = gradient.GetHeight() * ( ( factor + 1 ) / 2 );
    if ( y > gradient.GetHeight() - 1 )
    {
        y = gradient.GetHeight() - 1;
    }

    sf::Color col = gradient.GetPixel( 0, y );

    return col;
}

int main()
{
    noise::module::Perlin perlin;
    noise::model::Plane plane( perlin );

    sf::Vector2d pos( 2.D, 1.D );
    sf::Vector2i size( SIZE, SIZE );
    sf::Vector2d extent( 4.D, 4.D );
    sf::Vector2d end( pos.x + extent.x, pos.y + extent.y );
    sf::Vector2d delta( extent.x / size.x, extent.y / size.y );

    std::vector< std::vector< double > > values( size.x );
    for ( std::size_t ix = 0; ix < size.x; ++ix )
    {
        values[ ix ].resize( size.y );
    }

    for ( int ix = 0; ix < size.x; ++ix )
    {
        for ( int iy = 0; iy < size.y; ++iy )
        {
            sf::Vector2d current = pos;
            current.x += delta.x * ix;
            current.y += delta.y * iy;

            double value = plane.GetValue( current.x, current.y );

            values[ ix ][ iy ] = value;
        }
    }

    sf::Image gradient;
    GetGradient( gradient, GRADIENT );

    sf::Image img;
    img.Create( size.x, size.y, sf::Color::White );

    for ( int ix = 0; ix < size.x; ++ix )
    {
        for ( int iy = 0; iy < size.y; ++iy )
        {
            double value = values[ ix ][ iy ];
            value = ( value < -1.D ) ? -1.D : value;
            value = ( value >  1.D ) ?  1.D : value;

            img.SetPixel( ix, ( size.y - 1 ) - iy, GetColor( gradient, value ) );
        }
    }

    if ( !img.SaveToFile( "noise.png" ) )
    {
        std::cout << "Failed to save noise." << std::endl;
    }
    gradient.SaveToFile("gradient.png");
}