@workshop/compare

Compares two init/draw pairs on an offscreen 200*200 canvas. The canvas is instrumented with gl-reset in order to prevent state from leaking out and minimise the risk of memory leaks.

Returns a value between 0 and 1, where 1 is a complete match and 0 is a complete failure.

Accepts the following options:

opts.threshold

The maximum difference between two pixels before they're considered to no longer be matching. This is the total difference between the red, green, and blue channels and as such can range between 0 and 765.

opts.init

Pass in a custom hook for handling the init function of each submission/solution.

init: function(gl, initFn) {
  return initFn.call(gl, gl, imgElement)
}

opts.draw

Pass in a custom hook for handling the draw function of each submission/solution.

draw: function(gl, drawFn) {
  return drawFn.call(gl, gl, Date.now())
}

Example

Pseudocode for checking an exercise at 10 random intervals over a period of 5 seconds:

var times  = [Date.now()]
var passed = true

for (var i = 0; i < 9; i++) {
  times.push(times[0] + Math.random() * 5000)
}

for (var i = 0; i < times.length; i++) {
  passed = passed && compare(submission, solution, {
      threshold: 5
    , draw: function(gl, drawFn) {
      return drawFn.call(gl, gl, times[i])
    }
  })
}

done(null, passed)