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https://github.com/tent/sigil

Identicon generator
https://github.com/tent/sigil

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Identicon generator

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README 

        
# Sigil



![Sigil's inverted Sigil](https://sigil.cupcake.io/Sigil?inverted=1)

![Sigil's Sigil](https://sigil.cupcake.io/Sigil)



Sigil is a deterministic [identicon](https://en.wikipedia.org/wiki/Identicon)

generator.



Sigil creates a recognizable* identicon for each user that can be consistently

used across many sites when a user-uploaded avatar or Gravatar is unavailable or

unwanted. Sigils can be generated by any app or service using this application

or other implementation of the Sigil protocol. Sites can also use Sigil

[generation services](https://sigil.cupcake.io).



\* see _Privacy_ below



### Using Sigil



Sigil 0.1 creates identicons to represent _users_. A future release will have

additional algorithms and representations for non-persons. This will help anyone

who encounters Sigils to determine quickly if they represent users or other

content.



Sigil generates an identicon from a source string. In most cases (see _Privacy_)

the source string will be the user's email address. Query parameters can be used

to request an SVG or PNG of any size and switch the foreground and background

colors if desired. Reversing the background and foreground colors does not

change the information represented in a Sigil, so the reversed image can be used

if the style is more compatible with the host app.



You can generate Sigils internally using this app (or your own implementation of

the protocol below) or use a [Sigil service](https://sigil.cupcake.io).



The Sigil server takes an arbitrary string from the path and uses a MD5 of it to

generate the sigil. If you already have an MD5, you can hex encode it and the

server will not hash it again.



```text

https://sigil.cupcake.io/arbitrary

```



Simply replace `arbitrary` with data (for example a username) to get a Sigil.

You may optionally append `.png` or `.svg` to explicitly request a PNG or SVG

(PNG is the default). Two URL parameters are available:



- `w=240` sets the width in pixels (must be evenly divisible by 12). The default width is

  subject to change, so you should specify the width explicitly.

- `inverted=1` inverts the colors.



#### Privacy



There exists a possibility of significant user information disclosure if used

improperly. Email addresses should *not* be used as the source string (even if

hashed first) if the user's email address is not meant to be publicly available

through your site. It is possible to discover the email address from which the

Sigil was derived. This is a serious leak if the user's address is not exposed

elsewhere on the site. In these cases, use a *different* source string composed

of information that is available such as a username or user id.



### The Protocol



This repo contains a Sigil implementation written in Go, but Sigil can be

implemented in any language. A formal specification will be included with the

1.0 release.



Sigil uses the truncated MD5 hash of a string to create 5x5 identicons. The

first three columns and the color are generated from the truncated hash, the

last two columns are a reflection of the first two (1->5, 2->4).



### Roadmap



Sigil is still a work in progress. The color scheme is still being finalized and

this implementation may be optimized further. Additional background colors will

likely also be provided. We also intend to create a separate representation for

_things_ instead of _users_ i.e. favicons for Heroku apps. The suggested use

instructions (source string, background color, inverted colors, default width)

may also change before the 1.0 release.



### Try it



Download this repo or use [sigil.cupcake.io](https://sigil.cupcake.io) to

generate a Sigil.



Use Sigils in your own apps for users who don't have avatars or use your own

Sigil as an avatar in other apps.



[Ales Nesetril](http://www.alesnesetril.com/) designed the color scheme.



### Other implementations



- [Pydenticon](https://github.com/azaghal/pydenticon) (Python)