The URLs of variants imgproxy renders (Storehouse.Renderer): signed, so only the presets' sizes are ever rendered, and the same every time, for a CDN in front of it to keep. The app renders nothing, and stores nothing.

config :storehouse, Storehouse.Variants,
  renderer:
    {Storehouse.Renderer.Imgproxy,
     url: "https://images.example.com",
     key: System.fetch_env!("IMGPROXY_KEY"),
     salt: System.fetch_env!("IMGPROXY_SALT"),
     source: "s3://my-bucket/"},
  presets: [photo: [widths: [640, 1280, 1920], format: [:webp, :original]]]

A preset is written as imgproxy's processing options:

• a width alone is w:<width>; a box, rs:fit:<width>:<height>, or rs:fill:<width>:<height> with fit: :cover and its gravity (g:ce, g:sm for :attention and :entropy, g:fp:<x>:<y>);
• q:<quality>, when the preset gives one;
• f:<format> for one format; none for :original, or for several, which imgproxy chooses itself by Accept (with IMGPROXY_AUTO_WEBP or IMGPROXY_AUTO_AVIF on);
• scp:0 for profile: :keep, sm:0 for metadata: :all (imgproxy strips metadata by default), a background as bg:<hex>;
• then the preset's options: [imgproxy: "…"], as they are: "sh:0.3/fq:webp:86:jpeg:90".

imgproxy never enlarges an image unless it is told to.

Options

• :url - imgproxy's address (or the CDN's in front of it). Required.
• :key and :salt - imgproxy's, in hex (IMGPROXY_KEY, IMGPROXY_SALT). Without them, URLs are unsigned (/insecure/): for development only, as anyone could ask for any size.
• :source - where imgproxy reads the original: a prefix the key is put after ("s3://my-bucket/", "local:///"), or a function of the file that gives its address. The default is the store's URL of the file (Storehouse.url/2).
• :extension - true ends the URL with the format's extension (…/<source>.webp) in place of f:. The default is false.

Its own addresses

For URLs of another shape (a CDN's Worker that signs them itself), signed_path/2 gives the path imgproxy is asked, and a renderer of the app's own builds the rest.