Median is not correctly calculated about blockhash-js

[artfwo]

@dsoprea Thanks for reporting this here too :) Does the linked PR fix the problem?

[dsoprea]

Seems like it should, but I'm unable to test simply using Node.

1. Your package.json uses "devDependencies" instead of "dependencies", so the dependencies won't automatically install unless you pass "--dev" to npm-install.
2. When I adjusted this so that I could get the dependencies installed, I got an error about browser-specific functions missing (yes; I realize this might always require a URL, though I tried this with a local file first):

> b = require('blockhash')
{ hammingDistance: [Function: hammingDistance],
  blockhash: [Function: blockhash],
  blockhashData: [Function: blockhashData] }
> b.blockhash('test_assets/20170618_155330.jpg')
ReferenceError: XMLHttpRequest is not defined
    at Object.blockhash (/home/local/MAGICLEAP/doprea/development/node/testproject/node_modules/blockhash/index.js:217:15)
    at repl:1:3
    at sigintHandlersWrap (vm.js:22:35)
...

It seems like this project is singularly meant for use in webpages and not via Node. I'd remove any references to Node/NPM (including package.json; you'll have to make sure that all dependencies are represented properly in the webpage example) from the project/documentation while these issues exist, if indeed it was ever your intent for this to work in NPM, in order to mitigate confusion.

[dsoprea]

By the way, I could use some insight from you.

I had quickly translated the algorithm to Go based on your Python and C implementations (which is how I had noticed the median discrepancy). There is a subtle image-processing difference that might mean that all hashes produced using the standard Go image package will always differ from your hashes.

Send me an email, if you have a chance, to discuss.

[artfwo]

Right, the library is mostly for browsers, but it also works with node (one use case for that is running the tests outside of a browser). I am currently able to run the tests locally using:

npm install
npm install mocha (or add --dev to the above command)
./node_modules/mocha/bin/mocha

This should be probably documented. Mocha provides XMLHttpRequest, Date and other browser-specific stuff in the global namespace. The hashes currently match those from blockhash-python test data, so if you have no objections, I'd merge this change immediately. I'll send a follow-up email regarding your image processing differences ASAP.