* libee/conic.c:

+ ee_draw_ellipse().


git-svn-id: file:///srv/caca.zoy.org/var/lib/svn/ttyvaders/trunk@132 92316355-f0b4-4df1-b90c-862c8a59935f

libee/conic.c

@@ -47,3 +47,53 @@ void ee_draw_circle(int x, int y, int r, char c)
     }
 }
 
+static void ellipsepoints(int xo, int yo, int x, int y, char c)
+{
+    ee_putcharTO(xo + x, yo + y, c);
+    ee_putcharTO(xo - x, yo + y, c);
+    ee_putcharTO(xo + x, yo - y, c);
+    ee_putcharTO(xo - x, yo - y, c);
+}
+
+void ee_draw_ellipse(int xo, int yo, int a, int b, char c)
+{
+    int d2;
+    int x = 0;
+    int y = b;
+    int d1 = b*b - (a*a*b) + (a*a/4);
+
+    ellipsepoints(xo, yo, x, y, c);
+
+    while( a*a*y - a*a/2 > b*b*(x+1))
+    {
+        if(d1 < 0)
+        {
+            d1 += b*b*(2*x+1); /* XXX: "Computer Graphics" has + 3 here. */
+        }
+        else
+        {
+            d1 += b*b*(2*x*1) + a*a*(-2*y+2);
+            y--;
+        }
+        x++;
+        ellipsepoints(xo, yo, x, y, c);
+    }
+
+    d2 = b*b*(x+0.5)*(x+0.5) + a*a*(y-1)*(y-1) - a*a*b*b;
+    while(y > 0)
+    {
+        if(d2 < 0)
+        {
+            d2 += b*b*(2*x+2) + a*a*(-2*y+3);
+            x++;
+        }
+        else
+        {
+            d2 += a*a*(-2*y+3);
+        }
+
+        y--;
+        ellipsepoints(xo, yo, x, y, c);
+    }
+}
+

libee/ee.h

@@ -81,6 +81,7 @@ char ee_get_key(void);
 void ee_draw_line(int, int, int, int, char);
 void ee_draw_thin_line(int, int, int, int);
 void ee_draw_circle(int, int, int, char);
+void ee_draw_ellipse(int, int, int, int, char);
 void ee_fill_triangle(int, int, int, int, int, int, char);
 
 int ee_rand(int, int);