My first Lua

local img2=darktable.database.duplicate(img)
img2.apply_style(darktable.styles[1],img2)
local stor=darktable.modules.storage.disk
local format=darktable.modules.format.png
format.bpp=8
    darktable.modules.format.png.write_image(format,img2,darktable.configuration.tmp_dir.."/tmp.png");