metamask-extension/ui/lib/icon-factory.js

var iconFactory
const isValidAddress = require('ethereumjs-util').isValidAddress
const toChecksumAddress = require('ethereumjs-util').toChecksumAddress
const contractMap = require('eth-contract-metadata')

module.exports = function (jazzicon) {
  if (!iconFactory) {
    iconFactory = new IconFactory(jazzicon)
  }
  return iconFactory
}

function IconFactory (jazzicon) {
  this.jazzicon = jazzicon
  this.cache = {}
}

IconFactory.prototype.iconForAddress = function (address, diameter) {
  const addr = toChecksumAddress(address)
  if (iconExistsFor(addr)) {
    return imageElFor(addr)
  }
  return this.generateIdenticonSvg(address, diameter)
}

// returns svg dom element
IconFactory.prototype.generateIdenticonSvg = function (address, diameter) {
  var cacheId = `${address}:${diameter}`
  // check cache, lazily generate and populate cache
  var identicon = this.cache[cacheId] || (this.cache[cacheId] = this.generateNewIdenticon(address, diameter))
  // create a clean copy so you can modify it
  var cleanCopy = identicon.cloneNode(true)
  return cleanCopy
}

// creates a new identicon
IconFactory.prototype.generateNewIdenticon = function (address, diameter) {
  var numericRepresentation = jsNumberForAddress(address)
  var identicon = this.jazzicon(diameter, numericRepresentation)
  return identicon
}

// util

function iconExistsFor (address) {
  return (address in contractMap) && isValidAddress(address) && ('logo' in contractMap[address])
}

function imageElFor (address) {
  const contract = contractMap[address]
  const fileName = contract.logo
  const path = `images/contract/${fileName}`
  const img = document.createElement('img')
  img.src = path
  img.style.width = '100%'
  return img
}

function jsNumberForAddress (address) {
  var addr = address.slice(2, 10)
  var seed = parseInt(addr, 16)
  return seed
}