get("#356") -- num2hex

get("#348") -- rgb functions

function hashImage(img)

  local hash = 0

  local w, h = img.width, img.height

  for y = 0, h-1 do

    for x = 0, w-1 do

      local pix = img.getInt(x, y)

      local r, g, b = rgb(pix)

      local p = r+g*33+b*71

      local scale = bit32.band(y*w+x, 0xFFFF)+1

      --hash = (hash * a + pix) % 0x100000000

      --a = (a * b) % 0x100000000

      local arg = (p+1)*scale

      hash = bit32.bxor(hash, arg)

      --[[if x < 10 then

        print("scale", scale, "pix", pix, "p", p, "arg", arg, "hash", hash)

      end]]

    end

    --print("y", y, "hash", hash)

  end

  return num2hex(hash, 8)

end