procedure makebitmap(width,height)
   return open("bitmap", "g", "canvas=hidden",
             "size="||width||","||height)
end
procedure fillimage(w,color)
   Fg(w,color)
   FillRectangle(w)
end
procedure setpixel(w,x,y,color)
   Fg(w,color)
   DrawPixel(x,y)
end
procedure getpixel(w,x,y)
   return Pixel(w,x,y)
end