Computer-Graphic-Codes/Mid-point Ellipse.c at main · Jia2005/Computer-Graphic-Codes · GitHub

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#include <stdio.h>
#include <graphics.h>

void main() {
    long x, y, x_center, y_center;
    long a_sqr, b_sqr, fx, fy, d, a, b, tmp1, tmp2;
    int g_driver = DETECT, g_mode;

    clrscr();
    initgraph(&g_driver, &g_mode, "C:\\TURBOC3\\BGI");

    printf("\nEnter coordinate x and y = ");
    scanf("%ld%ld", &x_center, &y_center);

    printf("\nEnter the 2 radiuses = ");
    scanf("%ld%ld", &a, &b);

    x = 0;
    y = b;
    a_sqr = a * a;
    b_sqr = b * b;
    fx = 2 * b_sqr * x;
    fy = 2 * a_sqr * y;
    d = b_sqr - (a_sqr * b) + (a_sqr * 0.25);

    do {
        putpixel(x_center + x, y_center + y, 1);
        putpixel(x_center - x, y_center - y, 1);
        putpixel(x_center + x, y_center - y, 1);
        putpixel(x_center - x, y_center + y, 1);

        if (d < 0) {
            d = d + fx + b_sqr;
        } else {
            y = y - 1;
            d = d + fx - fy + b_sqr;
            fy = fy - (2 * a_sqr);
        }

        x = x + 1;
        fx = fx + (2 * b_sqr);
        delay(10);
    } while (fx < fy);

    tmp1 = (x + 0.5) * (x + 0.5);
    tmp2 = (y - 1) * (y - 1);
    d = b_sqr * tmp1 + a_sqr * tmp2 - (a_sqr * b_sqr);

    do {
        putpixel(x_center + x, y_center + y, 1);
        putpixel(x_center - x, y_center - y, 1);
        putpixel(x_center + x, y_center - y, 1);
        putpixel(x_center - x, y_center + y, 1);

        if (d >= 0) {
            d = d - fy + a_sqr;
        } else {
            x = x + 1;
            d = d + fx - fy + a_sqr;
            fx = fx + (2 * b_sqr);
        }

        y = y - 1;
        fy = fy - (2 * a_sqr);
    } while (y > 0);

    getch();
    closegraph();
}