MAth-Cloud-3.0.0/www.ipsocloud.com/intimamedia.com/cpp/MAth-Plaque-Dll-1.0.0/LibPlaque/Object/drawEllipse.cpp

/*****************************************************************
    Fichier     : DrawEllipse.cpp
    Date        : 07/01/11
    Version     : 1.000
    Description : Classe de dessin des ellipses
|*****************************************************************/
#include <cstdlib>
#include "drawEllipse.h"

CDrawEllipse::CDrawEllipse()
{
  top = 0; 
  bottom = 0; 
  left = 0; 
  right = 0; 
}

CDrawEllipse::~CDrawEllipse()    
{
}

void CDrawEllipse::PutPixEllipse(void (*ptFonction) (int, int), float xc,float yc,float x,float y)
{
	ptFonction( (int) (xc + x), (int) (yc + y));
	ptFonction( (int) (xc - x), (int) (yc - y));
	ptFonction( (int) (xc + x), (int) (yc - y));
	ptFonction( (int) (xc - x), (int) (yc + y));
}

// Algorithme MidPoint de dessin d'une Ellipse
void CDrawEllipse::myDrawEllipse(void (*ptFonction) (int, int))
{
	float x = 0, y = 0;
	double p1, p2, t1, t2;
	int k;
	float rx, ry, xc, yc;

	rx = (float) (right - left) / 2;
	ry = (float) (bottom - top) / 2;

	xc = left + rx;
	yc = top + ry;

	y = ry;
	p1 = ry * ry - rx * rx * ry + 0.25 * rx * rx;
    
	PutPixEllipse(ptFonction, xc, yc, x, y);

	for (k = 0; (2 * ry * ry * x) <= (2 * rx * rx * y); k++)
	{
		t1 = 2 * ry * ry * x + 2 * ry * ry;
		t2 = 2 * rx * rx * y - 2 * rx * rx;
		
		if (p1 < 0)
		{
			p1 = p1 + t1 + ry * ry;
		}
		else
		{
			p1 = p1 + t1 - t2 + ry * ry;
			y--;
		}

		x++;
		PutPixEllipse(ptFonction, xc, yc, x, y);
	}

	p2 = ry * ry * ( x + 0.5 ) * ( x + 0.5 ) + rx * rx * (y - 1) * (y - 1) - rx * rx * ry * ry;
	
	PutPixEllipse(ptFonction, xc, yc, x, y);

	for (k = 0 ; y >= 0 ;  k++)
	{
		t1 = 2 * ry * ry * x + 2 * ry * ry;
		t2 = 2 * rx * rx * y - 2 * rx * rx;
		
		if (p2 > 0)
		{
			p2 = p2 - t2 + rx * rx;
		}
		else
		{
			p2 = p2 + t1 - t2 + rx * rx;
			x++;
		}

		y--;
		PutPixEllipse(ptFonction, xc, yc, x, y);
	}

}