c++ libcinder mercator coordinates mapper

mercator.cpp

#include "Mercator.h"
#include "cinder/app/AppBasic.h"
#include "cinder/Vector.h"

using namespace ci;
using namespace std;
/* static method to map latitude and longitude to mercator 2d coords */
Vec2f Mercator::mapLatLon( const Vec2f lat_lon ) {
    /* mercator projection center was screen centered */
    Vec2f offset = Vec2f( app::getWindowWidth() / 2, app::getWindowHeight() / 2 );
    /* we need to place all the earth loft exactly at window area */
    float radius = app::getWindowWidth() / ( 2 * M_PI );
    /* yap, the simplest action in this method
     * lat_lon.x === latitude, lat_lon.y === longitude
     */
    float x = radius * lat_lon.y * M_PI / 180 + offset.x;
    /* here is the black magick */
    float y = offset.y - radius * ( log( tan( ( 90 + lat_lon.x ) * M_PI / 360 ) )  /  M_PI ) * 2.8f;
    
    return Vec2f( x, y );
}