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Mikubot/plugins/glitch.lua

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2015-07-28 20:37:10 +02:00
-- JPEG Glitcher v1.1
-- Contributed by Francesco <https://github.com/Francesco149>
do
local KILOBYTE = 1000
local MEGABYTE = KILOBYTE * 1000
function handle_http_response(code, status)
if code ~= 200 then
if status then
print(status)
else
print("http.request failed! (invalid url?)")
end
return false
end
return true
end
function get_jpg_header_size(data)
local res = 417
for i, byte in ipairs(data) do
if byte == 255 and data[i + 1] == 218 then
res = i + 2
break
end
end
return res
end
function simple_file_size(bytes)
local simplesize = bytes
local unit = "B"
if bytes >= MEGABYTE then
simplesize = simplesize / MEGABYTE
unit = "MB"
elseif bytes >= KILOBYTE then
simplesize = simplesize / KILOBYTE
unit = "KB"
end
return simplesize, unit
end
local GLITCH_MAX_FILE = MEGABYTE
function run(msg, matches)
http = require("socket.http")
local stamp = os.time()
-- try checking file size from a HEAD request
local default_timeout = http.TIMEOUT
http.TIMEOUT = 5
local _, code, headers, status = http.request {
url = matches[1],
method = "HEAD"
}
if not handle_http_response(code, status) then
return "HTTP request failed or file not found"
end
if not string.find(headers["content-type"], "jpeg") then
-- TODO: convert to jpg?
return "Not a JPEG file!"
end
local filesize = tonumber(headers["content-length"])
local response = nil
-- if the HEAD request doesn't contain content-length,
-- send a full GET request. the timeout will abort the request
-- after 5 seconds if the file is too large or takes too long
-- to download
if not filesize then
print("No content-length, performing a full request...")
response = http.request(matches[1])
filesize = #response
end
-- show user-friendly filesize
simplesize, unit = simple_file_size(filesize)
print("File Size: " .. simplesize .. unit .. " (" .. filesize .. " bytes)")
-- check filesize limit
if filesize > GLITCH_MAX_FILE then
return "Sorry, maximum filesize is " .. GLITCH_MAX_FILE / MEGABYTE .. "MB!"
end
-- if we previously got the file size through a HEAD request,
-- retrieve the actual data with a full request
if not response then
response, code, _, status = http.request(matches[1])
if not handle_http_response(code, status) then
return "HTTP request failed or file not found"
end
end
-- convert to byte array for manipulation
local arr = {}
response:gsub(".", function(c) table.insert(arr, string.byte(c)) end)
response = nil
-- skip jpeg header
local header_size = get_jpg_header_size(arr)
print("JPEG header size: " .. header_size .. " bytes")
-- corrupt a set amount of bytes
local data_end = #arr - 4
local corrupt_count = matches[2]
if not corrupt_count then
corrupt_count = 20
end
for i=1, corrupt_count do
local index = math.random(header_size, data_end)
print("Corrupting byte " .. index)
arr[index] = math.floor(math.random() * 255)
end
-- write glitched jpg
print("Writing glitched.jpg")
local out = assert(io.open("tmp/"..stamp..".jpg", "wb"))
local glitched = ""
for i=1, #arr do
out:write(string.char(arr[i]))
end
arr = nil
assert(out:close())
-- send glitched jpg
local receiver = get_receiver(msg)
send_photo(receiver, "tmp/"..stamp..".jpg", function() end, function() end)
http.TIMEOUT = default_timeout
end
return {
description = "Randomly glitches a JPEG image",
usage = "#glitch [url] [amount]: glitches the JPEG image retrieved from _url_ " ..
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"by corrupting _amount_ bytes. Amount is optional and defaults to 20 bytes.",
patterns = {
"^#glitch ([^ ]*) ([0-9]*)$",
"^#glitch ([^ ]*)$"
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},
run = run
}
end