EllipseFill

[SMcNeill]

Code: (Select All)

SUB EllipseFill (cx AS INTEGER, cy AS INTEGER, rx AS INTEGER, ry AS INTEGER, c AS LONG)
   DIM a AS LONG, b AS LONG
   DIM x AS LONG, y AS LONG
   DIM xx AS LONG, yy AS LONG
   DIM sx AS LONG, sy AS LONG
   DIM e AS LONG

   a = 2 * rx * rx
   b = 2 * ry * ry
   x = rx
   xx = ry * ry * (1 - rx - rx)
   yy = rx * rx
   sx = b * rx

   DO WHILE sx >= sy
       LINE (cx - x, cy - y)-(cx + x, cy - y), c, BF
       IF y <> 0 THEN LINE (cx - x, cy + y)-(cx + x, cy + y), c, BF

       y = y + 1
       sy = sy + a
       e = e + yy
       yy = yy + a

       IF (e + e + xx) > 0 THEN
           x = x - 1
           sx = sx - b
           e = e + xx
           xx = xx + b
       END IF
   LOOP

   x = 0
   y = ry
   xx = rx * ry
   yy = rx * rx * (1 - ry - ry)
   e = 0
   sx = 0
   sy = a * ry

   DO WHILE sx <= sy
       LINE (cx - x, cy - y)-(cx + x, cy - y), c, BF
       LINE (cx - x, cy + y)-(cx + x, cy + y), c, BF

       DO
           x = x + 1
           sx = sx + b
           e = e + xx
           xx = xx + b
       LOOP UNTIL (e + e + yy) > 0

       y = y - 1
       sy = sy - a
       e = e + yy
       yy = yy + a

   LOOP

END SUB