Network.Libravatar

Libravatar is a decentralized avatar delivery system. Instead of relying on a single centralized provider, it can use DNS records to detect the host of the avatar image. There is a server implementation which anyone can run and host their avatars and there are client libraries for many languages, all free-as-in-freedom software.

This module is a Haskell client library for Libravatar.

Note that this library doesn't actually fetch the image over HTTP. That part is left to the various HTTP client packages, such as http-client. What this library does is construct the image URL, possibly using DNS queries when needed for the decentralization. You can then fetch the image over HTTP or use the URL in your web app's HTML page templates, in which case the user's web brower will be downloading the image.

Now let's see how it works.

{-# LANGUAGE OverloadedStrings #-}
import Data.Default.Class (def)
import Network.Libravatar

Examples:

Email, HTTP, default fallback image (the libravatar logo), default size (80):

>>> avatarUrl (Email "[e-mail]") def
>>> { optSecure  = False
>>> , optDefault = ImgLibravatarLogo
>>> , optSize    = DefaultSize
>>> }
Just "http://cdn.libravatar.org/avatar/bc6a715808d9aae0ddeefb1e47e482a6"

Email, HTTPS, default fallback image, size 100. But now use an email with a domain which has SRV records for avatars:

>>> avatarUrl (Email "[e-mail]") def
>>> { optSecure  = True
>>> , optDefault = ImgLibravatarLogo
>>> , optSize    = Size 100
>>> }
Just "https://avatars.rel4tion.org:5679/avatar/e9e9ccabc2a166b1783bd7f4f9ceb376?s=100"

OpenID, HTTPS, specified fallback (special value "retro"), default size (80):

>>> avatarUrl (OpenID "https://examplibre.org/accounts/xyz/id") def
>>> { optSecure  = True
>>> , optDefault = ImgSpecial SpecialRetro
>>> , optSize    = DefaultSize
>>> }
Just "https://seccdn.libravatar.org/avatar/c2cbc5f5a1784fa7105380e550360d73f15c4c1f9c7ca1ac436c45a33027fcd7?d=retro"

(Note that the 2nd example uses dummy SRV records created by the author, and he isn't really running a Libravatar provider. This is just an example, the specific URL here will probably result with 404.)

Documentation

data UserAddress

User address for which to generate an avatar URL. Email or OpenID.

Constructors

Email Text

For example [e-mail]

OpenID Text

For example https://example.org/accounts/john/id

data SpecialImage

Special values available for the default image. The comments briefly explain the origin of the image/technique.

Constructors

SpecialMysteryPerson

A very simple outline of a person (constant image, does not vary by user address). Sometimes referred to as “mystery man”.

SpecialIdenticon

Geometric pattern based on a user address hash.

Origin: A visual representation of a hash value, usually of an IP address, that serves to identify a user of a computer system as a form of avatar while protecting the users' privacy.

SpecialMonsterID

A generated monster image with different colors, faces, etc.

Origin: A method to generate a unique monster image based upon a certain identifier (IP address, email address, etc.). It can be used to automatically provide personal avatar images in blog comments or other community services.

SpecialWavatar

A generated face with differing features and backgrounds.

Origin: Wavatars is a Wordpress plugin that will generate and assign icons to the visitors leaving comments at your site. The icons are based on email, so a given visitor will get the same icon each time they comment. It livens up comment threads and gives people memorable “faces” to aid in following conversation threads. It’s also fun.

SpecialRetro

A generated, 8-bit arcade-style pixelated face.

Origin: I don't know :P

data DefaultImage

What to do if the user's address isn't found in the Libravatar server's database.

Constructors

ImgLibravatarLogo

Don't specify a default image, let the server send its default image, which is the Libravatar logo (the orange butterfly).

ImgNotFound

Return HTTP 404 error (i.e. file not found) instead of an image.

ImgSpecial SpecialImage

Use one of the available special images or image generators.

ImgCustom Text

Use the given image URL as the default.

Instances

Default DefaultImage

data Size

Image size in pixels.

Constructors

Size Int

Use the given size. Acceptable values are between 1 and 512. Note that this library doesn't check the size you pass here, so make sure you pass a size within that range.

DefaultSize

Use the default size, which is 80 pixels.

Instances

Default Size

data AvatarOptions

Avatar details in addition to the user address itself. Define by starting with defOpts and override fields using record syntax.

Instances

Default AvatarOptions

optSecure :: AvatarOptions -> Bool

Whether the avatar URL should be secure (use HTTPS).

optDefault :: AvatarOptions -> DefaultImage

What to do if the user address isn't found in the Libravatar database.

optSize :: AvatarOptions -> Size

Image size in pixels.

optTryGravatar :: AvatarOptions -> Bool

If an image is not found in the Libravatar database, it can first redirect to gravatar in case the image exists there, and only then honour the optDefault parameter. This option sets whether Libravatar should try gravatar or go straight to the optDefault when an image isn't found.

avatarUrl :: UserAddress -> AvatarOptions -> IO (Maybe Text)

Return a URL to the avatar image.

If an error occurs, return Nothing. Currently, this happens only if the user address fails to be parsed.

See examples at the top of the page.