Add cache

[jperelli]

Think on how to add a directory/redis/memcache cache so that this can be used as a <img src="..."> tag more efficiently. Maybe add a cache param like

• cache=directory:path
• cache=redis:url
• cache=memcache:url
  and maybe use another param like cache_force_refresh=true to refresh cache, or a timeout like cache_timeout to expire old elements saved in cache

this module looks good enough https://www.npmjs.com/package/cache-manager
and this one to build the key from the options object https://www.npmjs.com/package/json-stable-stringify

[pascalroget]

as in - caching the binary images? If so, this will probably need an expires param as well

[jperelli]

Right, caching the binary images using the params (or hash of params) as key of the cache. That way only the first time the image is generated, but the next times is requested, the library just uses the cache to get and return the image fast.

And yes, I'll add an expires or timeout param for it to be auto purged