OpenEuphoria

circle.e - Reply

• Posted by "BABOR, JIRI" <J.Babor at GNS.CRI.NZ> Aug 05, 1997
• 1198 views

Last night, when I saw Lucius' creation, I thought there must be a better way.
The routine below is based on a bastardized Bresenham's algorithm, but only
partially unrolled for speed.
There is not much point in adding inferior routines to our collection, but this
one, at least, has a tile option, missing from the Euphoria version.

It is adapted from my virtual screen set of routines, which includes virtual
pixels, lines and tiled rectangles, ellipses and polygons, as well as the basic
virtual screen manipulation routines. No assembly, just high level Euphoria
routines, but they compare surprisingly well with build-in routines in mode 19.
I shall release them as soon as I find some time to write a decent demo and some
docs. In the meantime, if anybody is desperate enough, just mail me. Jiri.

-- ellipse.ex ------------------------------------------------------------------

-- Jiri Babor
-- j.babor at gns.cri.nz

include graphics.e
include get.e  -- wait_key()

object junk
sequence tile

procedure v_ellipse(object c,integer f,atom xc,atom yc,atom m,atom n)
   -- c is color or 2d tile sequence, f is fill flag
   -- xc,yc are centre coordinates, and m,n are major/minor radii
   sequence s
   integer x,y,dx,dy,r,rx,ry,xx,lx,ly,mx,my
   xc=floor(xc)
   yc=floor(yc)
   m=floor(m)
   n=floor(n)
   dx=2*m*m
   dy=2*n*n
   r=m*n*n
   rx=2*r
   ry=0
   x=m   y=0
   if not f then        -- hollow ellipse
      pixel(c,{xc-m,yc})
      pixel(c,{xc+m,yc})
      while x>0 do
         if r>0 then
            y=y+1
            ry=ry+dx
            r=r-ry
         end if
         if r<=0 then
            x=x-1
            rx=rx-dy
            r=r+rx
         end if
         pixel(c,{xc-x,yc-y})
         pixel(c,{xc+x,yc-y})
         pixel(c,{xc-x,yc+y})
         pixel(c,{xc+x,yc+y})
      end while
   elsif atom(c) then   -- filled ellipse: single color
      xx=m+m+1
      s=repeat(c,m+m+1)
      pixel(s,{xc-m,yc})
      while x>0 do
         if r>0 then
            y=y+1
            ry=ry+dx
            r=r-ry
         end if
         if r<=0 then
            x=x-1
            xx=xx-2
            rx=rx-dy
            r=r+rx
         end if
         pixel(s[1..xx],{xc-x,yc-y})
         pixel(s[1..xx],{xc-x,yc+y})
      end while
   else        -- tiled ellipse
      ly=length(c)
      lx=length(c[1])
      xx=m+m
      y=0
      s=c
      for i=1 to ly do
         while length(s[i])<xx+lx do s[i]=s[i]&c[i] end while
      end for
      mx=1+remainder(xc-x,lx)
      my=1+remainder(yc-y,ly)
      pixel(s[my][mx..mx+xx],{xc-x,yc})
      while x>0 do
         if r>0 then
            y=y+1
            ry=ry+dx
            r=r-ry
         end if
         if r<=0 then
            x=x-1
            xx=xx-2
            rx=rx-dy
            r=r+rx
         end if
         mx=1+remainder(xc-x,lx)
         my=1+remainder(yc-y,ly)
         pixel(s[my][mx..mx+xx],{xc-x,yc-y})
         my=1+remainder(yc+y,ly)
         pixel(s[my][mx..mx+xx],{xc-x,yc+y})
      end while
   end if
end procedure

-- examples --------------------------------------------------------------------

junk=graphics_mode(19)

      {9,14,14,14,9,9},{9,14,14,14,9,9}}
v_ellipse(tile,1,50,100,30,50)
v_ellipse(tile,1,200,100,100,50)
junk=wait_key()
junk=graphics_mode(-1)