Good sprite rotation

spriterotate.p8

-- rspr(spritesheetX,spritesheetY, screenX,screenY, angle, tileWidth, transColor)
-- tileWidth is squared when look at sprites. So a tileWidth=2 will do a 2x2 tile size (16x16) at sx,sy
function rspr(sx,sy,x,y,a,w,trans)
  local ca,sa=cos(a),sin(a)
  local srcx,srcy,addr,pixel_pair
  local ddx0,ddy0=ca,sa
  local mask=shl(0xfff8,(w-1))
  w*=4
  ca*=w
  sa*=w
  local dx0,dy0=sa-ca+w,-ca-sa+w
  w=2*w-1
  for ix=0,w do
   srcx,srcy=dx0,dy0
   for iy=0,w do
    if band(bor(srcx,srcy),mask)==0 then
     local c=sget(sx+srcx,sy+srcy)
     if c!=trans then
      pset(x+ix,y+iy,c)
     end
    end
    srcx-=ddy0
    srcy+=ddx0
   end
   dx0+=ddx0
   dy0+=ddy0
  end
 end