-- a box blur filter implemented in lua
--
-- seperation into two passes will greatly increase the
-- speed of this filter


edge_duplicate = 1
radius         = 4

local x,y

for y = 0, height-1 do
    for x = 0, width-1 do
       local count=0
       local rsum,gsum,bsum,asum=0,0,0,0
       for nx=x-radius, x+radius do
         for ny=y-radius, y+radius do
           local r,g,b,a= get_rgba (nx,ny)
           rsum,gsum,bsum,asum=rsum+r,gsum+g,bsum+b,asum+a
           count=count+1
         end
       end
       set_rgba (x,y, rsum/count,gsum/count,bsum/count,asum/count)
    end
    progress(y/height)
end