Nginx + Lua image resize

1_README.md

Nginx + Lua image resize

http://nginx.org/ru/docs/http/ngx_http_secure_link_module.html

2_nginx.conf

# ...
location ~ ^/image/(.*)$ {
  try_files $uri @resizer;
}

location @resizer {
  secure_link $arg_s;
  secure_link_md5 "$1 secret_word";

  if ($secure_link = "") {
    return 403;
  }

  proxy_pass http://127.0.0.1:81/$1;
  proxy_buffering on;
  proxy_store on;
  proxy_set_header Host $host;
}
# ...

3_nginx.conf

user nginx;
worker_processes auto;

error_log /dev/stderr warn;
pid /var/run/nginx.pid;

events {
    worker_connections 256;
}

http {
    access_log /dev/stdout;

    lua_code_cache on;
    lua_package_path 'conf/?.lua;;';

    init_by_lua_block {
        magick = require 'magick'
        math = require 'math'
    }

    server {
        listen 81;

        location ~ ^/(?<filter>resize|fit)/(?<width>\d+)x(?<height>\d+)/(?<path>.+)\.(?<format>jpg|png)$ {
            set $path "/var/uploads/$path";
            content_by_lua_file /srv/resizer.lua;
        }
    }
}

4_resizer.lua

ngx.req.discard_body()

local filter, path, format = ngx.var.filter, ngx.var.path, ngx.var.format
local width, height = tonumber(ngx.var.width), tonumber(ngx.var.height)

local img, error = magick.load_image(path)

if img == nil then
    ngx.log(ngx.ERR, error)
    return ngx.exit(415)
end

img:auto_orient()

if filter == 'fit' then
    img:resize_and_crop(width, height)
else
    local w, h = img:get_width(), img:get_height()
    local scale = math.min(width / w, height / h)
    img:resize(w * scale, h * scale)
end

if img:get_width() < 150 and img:get_height() < 150 then
    img:sharpen(1, 0)
end

if format == 'png' then
    img:set_format('png')
else
    img:set_format('jpeg')
end

img:set_quality(85)
img:set_interlace_scheme('PlaneInterlace')
img:strip()

ngx.print(img:get_blob())

return ngx.exit(ngx.HTTP_OK)

5_index.php

<?php
if (!function_exists('base64url_encode')) {
    function base64url_encode($data) 
    { 
        return rtrim(strtr(base64_encode($data), '+/', '-_'), '='); 
    }
}

const SECRET_WORD = 'secret_word';

function get_path_sign($path)
{
    return base64url_encode(md5($path.SECRET_WORD, true));
}

$path = 'resize/640x480/test.jpg';
printf('<img src="/image/%s?s=%s"/>', $path, get_path_sign($path)); // -> /image/resize/640x480/test.jpg?s=...