Moon phases - C++ Builder

 

private: // User declarations

    double __fastcall get_moon_phase(int year, int month, int day);

    void __fastcall DrawMoon(TCanvas *Canvas, int x, int y, int radius, double phase);

#include <vcl.h>

#include <System.SysUtils.hpp>

#include <time.h>

#include <math.h>

#pragma hdrstop

#include "p_Moon.h"

//---------------------------------------------------------------------------

#pragma package(smart_init)

#pragma resource "*.dfm"

TForm1 *Form1;

//---------------------------------------------------------------------------

__fastcall TForm1::TForm1(TComponent* Owner)

: TForm(Owner)

{

}

double __fastcall TForm1::get_moon_phase(int year, int month, int day)

{

if (month < 3) {

year--;

month += 12;

}

int A = year / 100;

int B = A / 4;

int C = 2 - A + B;

int E = (int)(365.25 * (year + 4716));

int F = (int)(30.6001 * (month + 1));

double jd = C + day + E + F - 1524.5;

double known_new_moon = 2451550.26;

double lunar_cycle = 29.530588853;

double days_since_new = jd - known_new_moon;

double cycles = days_since_new / lunar_cycle;

double phase = cycles - (long)cycles;

if (phase < 0) phase += 1;

return phase;

}

void __fastcall TForm1::DrawMoon(TCanvas *Canvas, int x, int y, int radius, double phase)

{

Canvas->Pen->Style = psSolid;

Canvas->Pen->Color = clGray;

Canvas->Brush->Color = clBlack;

Canvas->Brush->Style = bsSolid;

Canvas->Ellipse(x - radius, y - radius, x + radius, y + radius);

Canvas->Pen->Color = clYellow;

Canvas->Brush->Color = clYellow;

for (int i = -radius; i <= radius; i++) {

double w = sqrt((double)radius * radius - (double)i * i);

double terminatorX = w * cos(2.0 * M_PI * phase);

int xStart, xEnd;

if (phase <= 0.5) {

xStart = (int)(x + terminatorX);

xEnd   = (int)(x + w);

} else {

xStart = (int)(x - w);

xEnd   = (int)(x + terminatorX);

}

if (xStart < xEnd) {

Canvas->MoveTo(xStart, y + i);

Canvas->LineTo(xEnd, y + i);

}

}

Canvas->Brush->Style = bsClear;

Canvas->Pen->Color = clGray;

Canvas->Ellipse(x - radius, y - radius, x + radius, y + radius);

}

//---------------------------------------------------------------------------

void __fastcall TForm1::Timer1Timer(TObject *Sender)

{

  Label1->Caption=DateToStr(Date());

  Label4->Caption=TimeToStr(Time());

}

//---------------------------------------------------------------------------

void __fastcall TForm1::FormCreate(TObject *Sender)

{

 Button1->Caption="&Start";

 Button2->Caption="&Close";

}

//---------------------------------------------------------------------------

void __fastcall TForm1::Button2Click(TObject *Sender)

{

 Close();

}

//---------------------------------------------------------------------------

void __fastcall TForm1::Button1Click(TObject *Sender)

{

 int y,d,m;

 double phase, illumination;

 Word year,month,day;

 TDateTime today=Date();

 DecodeDate(today,year,month,day);

 y=(int)year;

 d=(int)day;

 m=(int)month;

 phase=get_moon_phase(y, m, d);

 illumination = (1 - cos(2 * M_PI * phase)) / 2 * 100;

 Label2->Caption="Lighting: "+FloatToStrF(illumination,ffGeneral,4,2)+"%";

 DrawMoon(Canvas, 200, 200, 100, phase);

}