BSD-3-Clause licensed and maintained by Mark Karpov
This version can be pinned in stack with:identicon-0.2.3@sha256:9ad2e006fc51842d2542d06ac79479f802d22ae1c32b4f7b943594bbdb30c4d5,2350

Module documentation for 0.2.3


License BSD3 Hackage Stackage Nightly Stackage LTS CI

The package implements a flexible framework for generation of identicons on top of Juicy Pixels.

Quick start

To use the package you usually need the following imports and language extensions:

{-# LANGUAGE DataKinds #-}
{-# LANGUAGE TypeOperators #-}

import Codec.Picture -- JuicyPixels
import Data.ByteString (ByteString) -- we use strict byte strings
import Data.Proxy
import Data.Word (Word8)
import Graphics.Identicon -- core definitions
import Graphics.Identicon.Primitive -- some visual primitives

You first write a type that represents the total number of bytes your identicon consumes and the number of distinct visual components it has (they are called “layers” in the terminology of the package):

type MyIcon = Identicon 12 :+ Consumer 4 :+ Consumer 4 :+ Consumer 4

Here we have an identicon that needs 12 bytes to be generated. It has three consumers that take 4 bytes each and generate layers, i.e. visual objects (circles, squares, etc.).

The second step is to write implementation of every layer. We can use the primitives available out-of-the-box, they live in the Graphics.Identicon.Primitive module:

myImpl :: Implementation MyIcon
myImpl = Identicon :+ a :+ a :+ a
    a :: Word8 -> Word8 -> Word8 -> Word8 -> Layer
    a r g b n =
      rsym $ onGrid 3 3 n $
        gradientXY (edge . mid) black (PixelRGB8 r g b)

Every byte is available to the layer-generating function as a distinct Word8 argument. The type system makes sure that:

  • you consume exactly as many bytes as you promised in the type of your identicon;

  • you have as many layers as you have described in the type of your identicon;

  • every function in your implementation has a correct signature (i.e. it takes as many Word8s as promised and produces a Layer in the end).

Mixing of layers and generation is handled by the library like this:

-- | Here is the function that generates your identicons. It's usually
-- convenient to wrap the 'renderIdenticon' function that comes with the
-- library.
genMyIdenticon ::
  -- | Identicon width
  Int ->
  -- | Identicon height
  Int ->
  -- | Input (some sort of hash or something)
  ByteString ->
  -- | Identicon, unless 'ByteString' is too short
  Maybe (Image PixelRGB8)
genMyIdenticon = renderIdenticon (Proxy :: Proxy MyIcon) myImpl

For more information head straight to the Haddocks. BTW, I have written a blog post about the package where I demonstrate some pictures generated with it.

Related packages

The following packages are designed to be used with identicon:


Issues, bugs, and questions may be reported in the GitHub issue tracker for this project.

Pull requests are also welcome.


Copyright © 2016–present Mark Karpov

Distributed under BSD 3 clause license.


Identicon 0.2.3

  • Maintenance release with newer dependencies.

Identicon 0.2.2

  • Improved documentation and metadata.

Identicon 0.2.1

  • Added Semigroup and Monoid instances for Layer.

Identicon 0.2.0

  • Added benchmarks.

  • Renamed applyWords to applyBytes (the method of type class ApplyBytes).

Identicon 0.1.0

  • Initial release.