Decrypts mangarock images into webp using lua programming language

mri_to_webp.lua

local moses = require("moses")


local function parse_mri_data_to_webp_buffer (mri_data)
    local size = #mri_data
    local webp_size = size + 7
    local webp_size_as_byte = string.pack("<I", webp_size)

    local webp_buffer = {
        82,  -- R
        73,  -- I
        70,  -- F
        70,  -- F
        string.byte(webp_size_as_byte:sub(1, 1)),
        string.byte(webp_size_as_byte:sub(2, 2)),
        string.byte(webp_size_as_byte:sub(3, 3)),
        string.byte(webp_size_as_byte:sub(4, 4)),
        87,  -- W
        69,  -- E
        66,  -- B
        80,  -- P
        86,  -- V
        80,  -- P
        56,  -- 8
    }

    for i=1, size do
        table.insert(webp_buffer, 101 ~ string.byte(mri_data:sub(i, i)))
    end

    return webp_buffer
end


local function buffer_to_data (buffer)
    return table.concat(moses.map(buffer, moses.ary(string.char, 1)), '')
end


local function parse_mri_to_webp (mri_path, webp_path)
    local fsi = io.open(mri_path, "rb")
    local mri_data = fsi:read("*all")
    fsi:close()

    local webp_buffer = parse_mri_data_to_webp_buffer(mri_data)
    local fso = io.open(webp_path, "wb")
    fso:write(buffer_to_data(webp_buffer))
    fso:close()
end


local function main (path_list)
    for _, path in pairs(path_list) do
        local base_path = string.gsub(path, "(%.%w+)$", '')
        parse_mri_to_webp(path, string.format("%s.webp", base_path))
    end
end


if arg[-1] then
    main(moses.slice(arg, 1))
end