"An Identicon is 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. The original Identicon was a 9-block graphic, and the representation has been extended to other graphic forms by third parties." – Wikipedia

NIdenticon is a library (available as NuGet package) that helps creating simple Identicons but is flexible enough to allow for tweaking the output to your heart's content.

This project was inspired by:

• Github – Identicons!
• David Hamp-Gonsalves – Generating Identicons
• Phil Haack – Identicons as Graphical Digital Fingerprints
• Jeff Atwood – Identicons for .NET

The most basic example is as follows:

var g = new IdenticonGenerator();
var mybitmap = g.Create("foo");

This will create an Identicon based on the string foo with all other options default; another example is:

var g = new IdenticonGenerator();
var mybitmap = g.Create(HttpContext.Current.Request.UserHostAddress);

This creates an Identicon based on the IP-address of a remote host. The Identicon can be created with the following options:

• Dimensions (width, height default: 400, 400)
• Number of blocks, or "pixels" (horizontal, vertical default: 6, 6)
• Hash algorithm (default: SHA512)
• Background color (default: Transparent)
• Even the default string-encoding used can be specified (default: UTF-8)

This library only contains one the IdenticonGenerator that has only one method: Create(), but which is rich in overloads. These are:

Bitmap Create(byte[] value)
Bitmap Create(byte[] value, Size size)
Bitmap Create(byte[] value, Size size, Color backgroundcolor)
Bitmap Create(byte[] value, Size size, Color backgroundcolor, Size blocks)
Bitmap Create(byte[] value, Size size, Color backgroundcolor, Size blocks, IBlockGenerator[] blockgenerators)
Bitmap Create(byte[] value, Size size, Color backgroundcolor, Size blocks, IBlockGenerator[] blockgenerators, IBrushGenerator brushgenerator)
Bitmap Create(byte[] value, Size size, Color backgroundcolor, Size blocks, IBlockGenerator[] blockgenerators, IBrushGenerator brushgenerator, string algorithm)
Bitmap Create(IPAddress ipaddress)
Bitmap Create(IPAddress ipaddress, Size size)
Bitmap Create(IPAddress ipaddress, Size size, Color backgroundcolor)
Bitmap Create(IPAddress ipaddress, Size size, Color backgroundcolor, Size blocks)
Bitmap Create(IPAddress ipaddress, Size size, Color backgroundcolor, Size blocks, IBlockGenerator[] blockgenerators)
Bitmap Create(IPAddress ipaddress, Size size, Color backgroundcolor, Size blocks, IBlockGenerator[] blockgenerators, IBrushGenerator brushgenerator)
Bitmap Create(IPAddress ipaddress, Size size, Color backgroundcolor, Size blocks, IBlockGenerator[] blockgenerators, IBrushGenerator brushgenerator, string algorithm)
Bitmap Create(string value)
Bitmap Create(string value, Size size)
Bitmap Create(string value, Size size, Color backgroundcolor)
Bitmap Create(string value, Size size, Color backgroundcolor, Size blocks)
Bitmap Create(string value, Size size, Color backgroundcolor, Size blocks, Encoding encoding)
Bitmap Create(string value, Size size, Color backgroundcolor, Size blocks, Encoding encoding, IBlockGenerator[] blockgenerators)
Bitmap Create(string value, Size size, Color backgroundcolor, Size blocks, Encoding encoding, IBlockGenerator[] blockgenerators, IBrushGenerator brushgenerator)
Bitmap Create(string value, Size size, Color backgroundcolor, Size blocks, Encoding encoding, IBlockGenerator[] blockgenerators, IBrushGenerator brushgenerator, string algorithm)

Parameters not specified will resort to the DefaultXXX-properties which can be specified when instantiating an IdenticonGenerator; the IdenticonGenerator's constructor is also rich in overloads:

public IdenticonGenerator()
public IdenticonGenerator(string algorithm)
public IdenticonGenerator(string algorithm, Size size)
public IdenticonGenerator(string algorithm, Size size, Color defaultBackgroundColor)
public IdenticonGenerator(string algorithm, Size size, Color defaultBackgroundColor, Size defaultBlocks)
public IdenticonGenerator(string algorithm, Size size, Color defaultBackgroundColor, Size defaultBlocks, Encoding encoding)
public IdenticonGenerator(string algorithm, Size size, Color defaultBackgroundColor, Size defaultBlocks, Encoding encoding, IBlockGenerator[] blockgenerators)
public IdenticonGenerator(string algorithm, Size size, Color defaultBackgroundColor, Size defaultBlocks, Encoding encoding, IBlockGenerator[] blockgenerators, IBrushGenerator brushgenerator)

_{(Ofcourse, the DefaultXXX properties can be changed after instantiating an IdenticonGenerator as well)}

This allows you to specify defaults only once (using the ctor) or for each generated Identicon (passing parameters to the Create() methods. Another approach is to use the fluent syntax to set only the desired defaults without having to specify all other parameters in the ctor:

var g = new IdenticonGenerator()
        .WithSize(96,96)
        .WithBlocks(6,6)
        .WithBlockGenerators(IdenticonGenerator.ExtendedBlockGeneratorsConfig);

Adhering to the SOLID principle, it is possible to create your own "BlockGenerators" and "BrushGenerators" by simply implementing their interfaces IBlockGenerator and IBrushGenerator. This way you can influence the shapes and colors of the Identicon. There are a few defaults provided as static members of the IdenticonGenerator class; these are:

• DefaultBlockGeneratorsConfig which only draws rectangles
• ExtendedBlockGeneratorsConfig which draws different kinds of shapes (triangles, pie-parts, rectangles and rotated rectangles)
• DefaultBrushGeneratorConfig which chooses a "random" (based on the input value to make the process deterministic) color.

Some BlockGenerators and BrushGenerators are provided; the rest is up to you. The blockgenerators are associated with a weight so that you can influence the probability of a blockgenerator to be chosen when the IdenticonGenerator is selecting a blockgenerator for a specific block in the Identicon.

#Notes

1. Do note that the Create() method and its overloads all return a Bitmap object; you have to take care of storing it, sending it to the browser or whatever you need to do. Also note that you might want to Dispose() the returned Identicon when no longer needed.

2. Also note that NIdenticon will round the image-dimensions DOWN to the nearest available size when the dimensions aren't exactly divisible by the horizontal/vertical blocks. Dimensions where width/horizontalblocks and height/verticalblocks are a multiple of oneanother work best (for example: for a width of 400 px you can use 2, 4, and 8 horizontal blocks but 6 will result in an image with a width of 396).

3. You might want to 'salt' your values (per Identicon (e.g. 'user' or 'account' for example) or per application, domain etc.) to make the Identicons even harder to 'reverse engineer'. A simple myIDGenerator.Create(user.Email + user.Salt) for example will do.

A simple Windows Forms application and sample ASP.Net MVC website is provided for you so you can explore the options and quickly see what the result will look like.

Below are some example images:

Result	Algorithm	Value	Blockgens	Background	Blocks	Brush
	MD5	Identicon	Default	White	6x6	Static
	MD5	Identicon	Extended	White	6x6	Static
	SHA256	Identicon	Extended	White	6x6	Static
	SHA512	Identicon	Extended	White	6x6	Static
	MD5	RobIII	Extended	Transparent	6x6	Random
	RipeMD160	RobIII	Extended	Transparent	6x6	Random
	SHA1	RobIII	Extended	Transparent	6x6	Random
	SHA256	RobIII	Extended	Transparent	6x6	Random
	SHA384	RobIII	Extended	Transparent	6x6	Random
	SHA512	RobIII	Extended	Transparent	6x6	Random
	SHA256	192.168.1.1	Extended	Transparent	6x6	Static
	SHA256	192.168.1.2	Extended	Transparent	6x6	Static
	SHA256	192.168.1.1	Extended	Black	6x6	Static
	SHA256	192.168.1.2	Extended	Black	6x6	Static
	SHA1	Foobar	Extended	Black	6x6	Static
	SHA1	FooBar	Extended	Black	6x6	Static
	MD5	foo_bar	Extended	Transparent	4x4	Static
	MD5	foo_bar	Extended	Transparent	6x6	Static
	MD5	foo_bar	Extended	Transparent	12x12	Static
	MD5	foo_bar	Default	Transparent	4x6	Static
	MD5	foo_bar	Default	Transparent	6x4	Static
	SHA256	Identicon	Extended	Transparent	6x6	Random
	SHA256	Identicon	Extended	Transparent	6x6	Static
	SHA384	Identicon	Custom (Triangles only)	Transparent	6x6	Random
	SHA384	Identicon	Custom (Pie-slices only)	Transparent	6x6	Random
	SHA384	Identicon	Custom (Rectangle + Pie in 4:1)	Transparent	6x6	Static

This module produces strong named assemblies when compiled. When consumers of this package require strongly named assemblies, for example when they themselves are signed, the outputs should work as-is. The key file to create the strong name is adjacent to the csproj file in the root of the source project. Please note that this does not increase security or provide tamper-proof binaries, as the key is available in the source code per Microsoft guidelines