demo-04-20/demo.lua

local bitmap = require'bitmap' --used to read its content

do --open image
  local cairo = require'cairo' --used to open the file
  local image = cairo.load_png(arg[1])
  image_infos = {width = image:width(), height = image:height()}
  image_bitmap = image:bitmap()
end
local getpixel, setpixel = bitmap.pixel_interface(image_bitmap)
print(image_infos.width, image_infos.height)