Code viewer for World: Character recognition neur...

// Cloned by Luke Scales on 30 Nov 2019 from World "Character recognition neural network" by "Coding Train" project 
// Please leave this clone trail here.
 

// Port of Character recognition neural network from here:
// https://github.com/CodingTrain/Toy-Neural-Network-JS/tree/master/examples/mnist
// with many modifications 

// TODO: classifier working, pre-train model using mnist database or figure out how to train live in browser
// 

// --- defined by MNIST - do not change these ---------------------------------------

const PIXELS        = 28;                       // images in data set are tiny 
const PIXELSSQUARED = PIXELS * PIXELS;

// number of training and test exemplars in the data set:
const NOTRAIN = 60000;
const NOTEST  = 10000;



//--- can modify all these --------------------------------------------------

// no of nodes in network 
const noinput  = PIXELSSQUARED;
const nohidden = 64;
const nooutput = 10;

const learningrate = 0.1;   // default 0.1  

// should we train every timestep or not 
let do_training = true;

// how many to train and test per timestep 
const TRAINPERSTEP = 30;
const TESTPERSTEP  = 5;

// multiply it by this to magnify for display 
const ZOOMFACTOR    = 7;                        
const ZOOMPIXELS    = ZOOMFACTOR * PIXELS; 

// 3 rows of
// large image + 50 gap + small image    
// 50 gap between rows 

const canvaswidth = ( PIXELS + ZOOMPIXELS ) + 50;
const canvasheight = ( ZOOMPIXELS * 3 ) + 100;


const DOODLE_THICK = 18;    // thickness of doodle lines 
const DOODLE_BLUR = 3;      // blur factor applied to doodles 


let mnist;      
// all data is loaded into this 
// mnist.train_images
// mnist.train_labels
// mnist.test_images
// mnist.test_labels

let classifier;


let nn;

let trainrun = 1;
let train_index = 0;

let testrun = 1;
let test_index = 0;
let total_tests = 0;
let total_correct = 0;

// images in LHS:
let doodle, demo;
let doodle_exists = false;
let demo_exists = false;

let mousedrag = false;      // are we in the middle of a mouse drag drawing?  


// save inputs to global var to inspect
// type these names in console 
var train_inputs, test_inputs, demo_inputs, doodle_inputs;


// Matrix.randomize() is changed to point to this. Must be defined by user of Matrix. 

function randomWeight()
{
    return ( AB.randomFloatAtoB ( -0.5, 0.5 ) );
            // Coding Train default is -1 to 1
}    



// CSS trick 
// make run header bigger 
 $("#runheaderbox").css ( { "max-height": "95vh" } );


//--- start of AB.msgs structure: ---------------------------------------------------------
// We output a serious of AB.msgs to put data at various places in the run header 
var thehtml;

  // 1 Doodle header 
  thehtml = "<hr> <h1> 1. Doodle </h1> Top row: Doodle (left) and shrunk (right). <br> " +
        " Draw your doodle in top LHS. <button onclick='wipeDoodle();' class='normbutton' >Clear doodle</button> <br> ";
   AB.msg ( thehtml, 1 );

  // 2 Doodle variable data (guess)
  
  // 3 Training header
  thehtml = "<hr> <h1> 2. Training </h1> Middle row: Training image magnified (left) and original (right). <br>  " +
        " <button onclick='do_training = false;' class='normbutton' >Stop training</button> <br> ";
  AB.msg ( thehtml, 3 );
     
  // 4 variable training data 
  
  // 5 Testing header
  thehtml = "<h3> Hidden tests </h3> " ;
  AB.msg ( thehtml, 5 );
           
  // 6 variable testing data 
  
  // 7 Demo header 
  thehtml = "<hr> <h1> 3. Demo </h1> Bottom row: Test image magnified (left) and  original (right). <br>" +
        " The network is <i>not</i> trained on any of these images. <br> " +
        " <button onclick='makeDemo();' class='normbutton' >Demo test image</button> <br> ";
   AB.msg ( thehtml, 7 );
   
  // 8 Demo variable data (random demo ID)
  // 9 Demo variable data (changing guess)
  
const greenspan = "<span style='font-weight:bold; font-size:x-large; color:darkgreen'> "  ;

//--- end of AB.msgs structure: ---------------------------------------------------------




function setup() 
{
  createCanvas ( canvaswidth, canvasheight );

  doodle = createGraphics ( ZOOMPIXELS, ZOOMPIXELS );       // doodle on larger canvas 
  doodle.pixelDensity(1);
  
// JS load other JS 
// maybe have a loading screen while loading the JS and the data set 

      AB.loadingScreen();
      
var TFurl = 'https://unpkg.com/@tensorflow/tfjs';
// var MNurl = 'https://unpkg.com/@tensorflow-models/mobilenet';
// var ml5url = 'https://unpkg.com/ml5@0.4.3/dist/ml5.min.js'
$.getScript( TFurl, function() {
    console.log('tensorflow.js loaded');
});

var head = document.getElementsByTagName('head')[0];
var script = document.createElement('script');
script.type = 'text/javascript';
script.onload = function() {
    console.log('tf inserted');
}
script.src = TFurl;
head.appendChild(script);

var tfVisUrl = "https://cdn.jsdelivr.net/npm/@tensorflow/tfjs-vis@1.0.2/dist/tfjs-vis.umd.min.js";
// "https://cdn.jsdelivr.net/npm/@tensorflow/tfjs-vis@1.0.2/dist/tfjs-vis.umd.min.js"
// const dataFileUrl = "uploads/lukescales/data.js";
$.getScript( tfVisUrl, function() {
    console.log('tfvis loaded');
    run();
});
// import {MnistData} from "uploads/lukescales/model.jsons"; 

// import('uploads/lukescales/model.jsons')
//       .then(module => {
//         console.log(module.nistData());
//       })
//       .catch(err => {
//         console.log('nope', err);
//       });

// var head = document.getElementsByTagName('head')[0];
// var newScript = document.createElement('script');
// script.type = 'text/javascript';
// script.onload = function() {
//     console.log('tf inserted');
    
// }
// script.src = TFurl;
// head.appendChild(script);

// const canvasEl = '<div id="result_box"><canvas id="chart_box" width="100" height="100"></canvas></div>'
// const insertPoint = document.getElementById('wrapper');
// insertPoint.innerHTML += canvasEl;

// $.getScript( MNurl, function() {
//     console.log('mobilenet script loaded');
// });

// $.getScript( ml5url, function() {
//     console.log('ml5 script loaded');
//     classifier = ml5.imageClassifier('uploads/lukescales/model.json');
// });
const chartjsurl = "https://cdnjs.cloudflare.com/ajax/libs/Chart.js/2.4.0/Chart.min.js";
$.getScript ( chartjsurl, function() {
    console.log('chartjs loaded');
});
 
 $.getScript ( "/uploads/codingtrain/matrix.js", function()
 {
   $.getScript ( "/uploads/codingtrain/nn.js", function()
   {
        $.getScript ( "/uploads/codingtrain/mnist.js", function()
        {
            console.log ("All JS loaded");
            nn = new NeuralNetwork(  noinput, nohidden, nooutput );
            nn.setLearningRate ( learningrate );
            loadData();
            console.log(MnistData);
        });
   });
 });
}



// load data set from local file (on this server)

function loadData()    
{
  loadMNIST ( function(data)    
  {
    mnist = data;
    console.log ("All data loaded into mnist object:")
    console.log(mnist);
    AB.removeLoading();     // if no loading screen exists, this does nothing 
  });
}



function getImage ( img )      // make a P5 image object from a raw data array   
{
    let theimage  = createImage (PIXELS, PIXELS);    // make blank image, then populate it 
    theimage.loadPixels();        
    
    for (let i = 0; i < PIXELSSQUARED ; i++) 
    {
        let bright = img[i];
        let index = i * 4;
        theimage.pixels[index + 0] = bright;
        theimage.pixels[index + 1] = bright;
        theimage.pixels[index + 2] = bright;
        theimage.pixels[index + 3] = 255;
    }
    
    theimage.updatePixels();
    return theimage;
}


function getInputs ( img )      // convert img array into normalised input array 
{
    let inputs = [];
    for (let i = 0; i < PIXELSSQUARED ; i++)          
    {
        let bright = img[i];
        inputs[i] = bright / 255;       // normalise to 0 to 1
    } 
    return ( inputs );
}

 

function trainit (show)        // train the network with a single exemplar, from global var "train_index", show visual on or off 
{
  let img   = mnist.train_images[train_index];
  let label = mnist.train_labels[train_index];
  
  // optional - show visual of the image 
  if (show)                
  {
    var theimage = getImage ( img );    // get image from data array 
    image ( theimage,   0,                ZOOMPIXELS+50,    ZOOMPIXELS,     ZOOMPIXELS  );      // magnified 
    image ( theimage,   ZOOMPIXELS+50,    ZOOMPIXELS+50,    PIXELS,         PIXELS      );      // original
  }

  // set up the inputs
  let inputs = getInputs ( img );       // get inputs from data array 

  // set up the outputs
  let targets = [0, 0, 0, 0, 0, 0, 0, 0, 0, 0];
  targets[label] = 1;       // change one output location to 1, the rest stay at 0 

  // console.log(train_index);
  // console.log(inputs);
  // console.log(targets);

  train_inputs = inputs;        // can inspect in console 
  nn.train ( inputs, targets );

  thehtml = " trainrun: " + trainrun + "<br> no: " + train_index ;
  AB.msg ( thehtml, 4 );

  train_index++;
  if ( train_index == NOTRAIN ) 
  {
    train_index = 0;
    console.log( "finished trainrun: " + trainrun );
    trainrun++;
  }
}


function testit()    // test the network with a single exemplar, from global var "test_index"
{ 
  let img   = mnist.test_images[test_index];
  let label = mnist.test_labels[test_index];

  // set up the inputs
  let inputs = getInputs ( img ); 
  
  test_inputs = inputs;        // can inspect in console 
  let prediction    = nn.predict(inputs);       // array of outputs 
  let guess         = findMax(prediction);      // the top output 

  total_tests++;
  if (guess == label)  total_correct++;

  let percent = (total_correct / total_tests) * 100 ;
  
  thehtml =  " testrun: " + testrun + "<br> no: " + total_tests + " <br> " +
        " correct: " + total_correct + "<br>" +
        "  score: " + greenspan + percent.toFixed(2) + "</span>";
  AB.msg ( thehtml, 6 );

  test_index++;
  if ( test_index == NOTEST ) 
  {
    console.log( "finished testrun: " + testrun + " score: " + percent.toFixed(2) );
    testrun++;
    test_index = 0;
    total_tests = 0;
    total_correct = 0;
  }
}




//--- find no.1 (and maybe no.2) output nodes ---------------------------------------
// (restriction) assumes array values start at 0 (which is true for output nodes) 


function find12 (a)         // return array showing indexes of no.1 and no.2 values in array 
{
  let no1 = 0;
  let no2 = 0;
  let no1value = 0;     
  let no2value = 0;
  
  for (let i = 0; i < a.length; i++) 
  {
    if (a[i] > no1value) 
    {
      no1 = i;
      no1value = a[i];
    }
    else if (a[i] > no2value) 
    {
      no2 = i;
      no2value = a[i];
    }
  }
  
  var b = [ no1, no2 ];
  return b;
}


// just get the maximum - separate function for speed - done many times 
// find our guess - the max of the output nodes array

function findMax (a)        
{
  let no1 = 0;
  let no1value = 0;     
  
  for (let i = 0; i < a.length; i++) 
  {
    if (a[i] > no1value) 
    {
      no1 = i;
      no1value = a[i];
    }
  }
  
  return no1;
}




// --- the draw function -------------------------------------------------------------
// every step:
var clickX = new Array();
var clickY = new Array();
var clickD = new Array();
 
function draw() 
{
  // check if libraries and data loaded yet:
  if ( typeof mnist == 'undefined' ) return;


// how can we get white doodle on black background on yellow canvas?
//        background('#ffffcc');    doodle.background('black');

      background ('black');
    
if ( do_training )    
{
  // do some training per step 
    for (let i = 0; i < TRAINPERSTEP; i++) 
    {
      if (i == 0)    trainit(true);    // show only one per step - still flashes by  
      else           trainit(false);
    }
    
  // do some testing per step 
    for (let i = 0; i < TESTPERSTEP; i++) 
      testit();
}

  // keep drawing demo and doodle images 
  // and keep guessing - we will update our guess as time goes on 
  
  if ( demo_exists )
  {
    drawDemo();
    guessDemo();
  }
  if ( doodle_exists ) 
  {
    drawDoodle();
    // guessDoodle();
  }


// detect doodle drawing 
// (restriction) the following assumes doodle starts at 0,0 

  if ( mouseIsPressed )         // gets called when we click buttons, as well as if in doodle corner  
  {
     // console.log ( mouseX + " " + mouseY + " " + pmouseX + " " + pmouseY );
     var MAX = ZOOMPIXELS + 20;     // can draw up to this pixels in corner 
     if ( (mouseX < MAX) && (mouseY < MAX) && (pmouseX < MAX) && (pmouseY < MAX) )
     {
        mousedrag = true;       // start a mouse drag 
        doodle_exists = true;
        doodle.stroke('white');
        doodle.strokeWeight( DOODLE_THICK );
        doodle.line(mouseX, mouseY, pmouseX, pmouseY);
        clickX.push(mouseX);
        clickY.push(mouseY);
     }
  }
  else 
  {
      // are we exiting a drawing
      if ( mousedrag )
      {
            mousedrag = false;
            // console.log ("Exiting draw. Now blurring.");
            doodle.filter (BLUR, DOODLE_BLUR);    // just blur once 
            //   console.log (doodle);
      }
  }
}

function boundingBox() {
  var minX = Math.min.apply(Math, clickX) - 20;
  var maxX = Math.max.apply(Math, clickX) + 20;
  
  var minY = Math.min.apply(Math, clickY) - 20;
  var maxY = Math.max.apply(Math, clickY) + 20;

  var tempCanvas = document.createElement("canvas"),
  tCtx = tempCanvas.getContext("2d");

  tempCanvas.width  = maxX - minX;
  tempCanvas.height = maxY - minY;

  tCtx.drawImage(canvas, minX, minY, maxX - minX, maxY - minY, 0, 0, maxX - minX, maxY - minY);

  var imgBox = document.getElementById("chart_box");
  imgBox.src = tempCanvas.toDataURL();

  return tempCanvas;
}



//--- demo -------------------------------------------------------------
// demo some test image and predict it
// get it from test set so have not used it in training


function makeDemo()
{
    demo_exists = true;
    var  i = AB.randomIntAtoB ( 0, NOTEST - 1 );  
    
    demo        = mnist.test_images[i];     
    var label   = mnist.test_labels[i];
    
   thehtml =  "Test image no: " + i + "<br>" + 
            "Classification: " + label + "<br>" ;
   AB.msg ( thehtml, 8 );
   
   // type "demo" in console to see raw data 
}


function drawDemo()
{
    var theimage = getImage ( demo );
     //  console.log (theimage);
     
    image ( theimage,   0,                canvasheight - ZOOMPIXELS,    ZOOMPIXELS,     ZOOMPIXELS  );      // magnified 
    image ( theimage,   ZOOMPIXELS+50,    canvasheight - ZOOMPIXELS,    PIXELS,         PIXELS      );      // original
}


function guessDemo()
{
   let inputs = getInputs ( demo ); 
   
  demo_inputs = inputs;  // can inspect in console 
  
  let prediction    = nn.predict(inputs);       // array of outputs 
  let guess         = findMax(prediction);      // the top output 

   thehtml =   " We classify it as: " + greenspan + guess + "</span>" ;
   AB.msg ( thehtml, 9 );
}




//--- doodle -------------------------------------------------------------

function drawDoodle()
{
    // doodle is createGraphics not createImage
    let theimage = doodle.get();
    // console.log (theimage);
    
    image ( theimage,   0,                0,    ZOOMPIXELS,     ZOOMPIXELS  );      // original 
    image ( theimage,   ZOOMPIXELS+50,    0,    PIXELS,         PIXELS      );      // shrunk
}


function preprocessCanvas(image, modelName) {

  // if model is not available, send the tensor with expanded dimensions
  if (modelName === undefined) {
    alert("No model defined..")
  } 

  // if model is digitrecognizermlp, perform all the preprocessing
  else if (modelName === "a") {
    
    // resize the input image to digitrecognizermlp's target size of (784, )
    let tensor = tf.browser.fromPixels(image)
        .resizeNearestNeighbor([28, 28])
        .mean(2)
        .toFloat()
        .reshape([1 , 784]);
    return tensor.div(255.0);
  }

  // if model is digitrecognizercnn, perform all the preprocessing
  else if (modelName === "b") {
    // resize the input image to digitrecognizermlp's target size of (1, 28, 28, 1)
    let tensor = tf.browser.fromPixels(image)
        .resizeNearestNeighbor([28, 28])
        .mean(2)
        .expandDims(2)
        .expandDims()
        .toFloat();
    console.log(tensor.shape);
    return tensor.div(255.0);
  }

  // else throw an error
  else {
    alert("Unknown model name..")
  }
}


//------------------------------
// Chart to display predictions
//------------------------------
var chart = "";
var firstTime = 0;
function loadChart(label, data, modelSelected) {
  var context = document.getElementById('chart_box').getContext('2d');
  chart = new Chart(context, {
      // we are in need of a bar chart
      type: 'bar',

      // we feed in data dynamically using data variable
      // that is passed as an argument to this function
      data: {
          labels: label,
          datasets: [{
              label: modelSelected + " prediction",
              backgroundColor: '#f50057',
              borderColor: 'rgb(255, 99, 132)',
              data: data,
          }]
      },

      // you can also play around with options for the 
      // chart if you find time!
      options: {}
  });
}

//----------------------------
// display chart with updated
// drawing from canvas
//----------------------------
function displayChart(data) {
  var select_model  = document.getElementById("select_model");
//   var select_option = select_model.options[select_model.selectedIndex].value;
    var select_option = 'a';
  
  label = ["0", "1", "2", "3", "4", "5", "6", "7", "8", "9"];
  if (firstTime == 0) {
    loadChart(label, data, select_option);
    firstTime = 1;
  } else {
    chart.destroy();
    loadChart(label, data, select_option);
  }
  document.getElementById('chart_box').style.display = "block";
}

async function classify() {
//     let net;
//   console.log('Loading mobilenet..');

  // Load the model.
//   net = await mobilenet.load();
//   console.log('Successfully loaded model');

    classifier = await tf.loadLayersModel('uploads/lukescales/processed_model_v2.2_update.json');
    console.log(classifier);

    // const imgEl = document.getElementById('defaultCanvas0');
    // const doodle = tf.browser.fromPixels(imgEl);
    
    // const img = doodle.get();
    // img.resize ( PIXELS, PIXELS );     
    // img.loadPixels();

  // set up inputs   
//   let inputs = [];
//   for (let i = 0; i < PIXELSSQUARED ; i++) 
//   {
//      inputs[i] = img.pixels[i] / 255;
//   }
  
//   const canvas = document.getElementById('defaultCanvas0');
// const ctx = canvas.getContext('2d');
// const imageData = ctx.createImageData(28, 28);

// // Iterate through every pixel
// for (let i = 0; i < imageData.data.length; i += 4) {
//   // Modify pixel data
//   imageData.data[i + 0] = 190;  // R value
//   imageData.data[i + 1] = 0;    // G value
//   imageData.data[i + 2] = 210;  // B value
//   imageData.data[i + 3] = 255;  // A value
// }

// // Draw image data to the canvas
// ctx.putImageData(imageData, 28, 28);
  
//   doodle_inputs = inputs;
    // const imgEl = doodle.get();
//   const result = await net.classify(imgEl);
    // tfimg = createImage(28, 28);
    // tfimg.loadPixels();
    // for (let x = 0; x < tfimg.width; x++) {
    //   for (let y = 0; y < tfimg.height; y++) {
    //     let a = map(y, 0, tfimg.height, 255, 0);
    //     tfimg.set(x, y, [0, 153, 204, a]);
    //   }
    // }
    // tfimg.updatePixels();
    // 
// image.data[0] = 100;
// image.data[1] = 150;
// image.data[2] = 200;
// image.data[3] = 255;

// tf.browser.fromPixels(image)
    // const uint8arr = Uint8ClampedArray.from(inputs);
    // const image = new ImageData(uint8arr, 28, 28);
    
    const img = doodle.get();
    img.resize ( PIXELS, PIXELS );     
    img.loadPixels();
    // img.pixels = img.pixels / 255.0;
    img.pixels = img.pixels;
    // const image = new ImageData(img.pixels, 28, 28);
    // let inputs = getInputs ( demo );
    const uint8arr = Uint8ClampedArray.from(img.pixels);
    const image = new ImageData(uint8arr, 28, 28);
    
    // get the user drawn region alone cropped
//   croppedCanvas = boundingBox();

  // show the cropped image 
//   document.getElementById("canvas_output").style.display = "block"

    // const tensor = tf.browser.fromPixels(image);
    // const tensor =  preprocessCanvas(croppedCanvas, 'b');
    let tensor = tf.browser.fromPixels(image)
        .resizeNearestNeighbor([28, 28])
        .mean(2)
        .expandDims(2)
        .expandDims();
        // .toFloat();
    console.log(tensor);
    console.log(tensor.shape);
    tensor.div(255.0);
    console.log(tensor);
    console.log(tensor.shape);
    // const prediction = await classifier.predict(tensor).bytes();
     let prediction = await classifier.predict(tensor).data();

//   // get the model's prediction results
  let results = Array.from(prediction)

//   // display the predictions in chart
  displayChart(results)

  console.log(results);
    console.log(prediction);
}

      
function guessDoodle() 
{
   // doodle is createGraphics not createImage
   let img = doodle.get();
  
  img.resize ( PIXELS, PIXELS );     
  img.loadPixels();

  // set up inputs   
  let inputs = [];
  for (let i = 0; i < PIXELSSQUARED ; i++) 
  {
     inputs[i] = img.pixels[i * 4] / 255;
  }
  
  doodle_inputs = inputs;     // can inspect in console 

  // feed forward to make prediction 
  let prediction    = nn.predict(inputs);       // array of outputs 
  let b             = find12(prediction);       // get no.1 and no.2 guesses  

  thehtml =   " We classify it as: " + greenspan + b[0] + "</span> <br>" +
            " No.2 guess is: " + greenspan + b[1] + "</span>";
  AB.msg ( thehtml, 2 );
}

function gotResult(error, results) {
  // Display error in the console
  if (error) {
    console.error(error);
  }
  // The results are in an array ordered by confidence.
  console.log(results);
  // Show the first label and confidence
//   label.html('Label: ' + results[0].label);
//   confidence.html('Confidence: ' + nf(results[0].confidence, 0, 2)); // Round the confidence to 0.01
    thehtml =   'Label: ' + results[0].label +
            'Confidence: ' + nf(results[0].confidence, 0, 2);
  AB.msg ( thehtml, 2 );
}


function wipeDoodle()    
{
    classify();
    // classifier.classify(doodle, gotResult);
    setTimeout(function() { 
        doodle_exists = false;
        doodle.background('black');
        
    }, 3000);
    
}




// --- debugging --------------------------------------------------
// in console
// showInputs(demo_inputs);
// showInputs(doodle_inputs);


function showInputs ( inputs )
// display inputs row by row, corresponding to square of pixels 
{
    var str = "";
    for (let i = 0; i < inputs.length; i++) 
    {
      if ( i % PIXELS == 0 )    str = str + "\n";                                   // new line for each row of pixels 
      var value = inputs[i];
      str = str + " " + value.toFixed(2) ; 
    }
    console.log (str);
}

// Data.js content
const IMAGE_SIZE = 784;
const NUM_CLASSES = 10;
const NUM_DATASET_ELEMENTS = 65000;

const TRAIN_TEST_RATIO = 5 / 6;

const NUM_TRAIN_ELEMENTS = Math.floor(TRAIN_TEST_RATIO * NUM_DATASET_ELEMENTS);
const NUM_TEST_ELEMENTS = NUM_DATASET_ELEMENTS - NUM_TRAIN_ELEMENTS;

const MNIST_IMAGES_SPRITE_PATH =
    'https://storage.googleapis.com/learnjs-data/model-builder/mnist_images.png';
const MNIST_LABELS_PATH =
    'https://storage.googleapis.com/learnjs-data/model-builder/mnist_labels_uint8';

/**
 * A class that fetches the sprited MNIST dataset and returns shuffled batches.
 *
 * NOTE: This will get much easier. For now, we do data fetching and
 * manipulation manually.
 */
// class MnistData {
//   constructor() {
//     this.shuffledTrainIndex = 0;
//     this.shuffledTestIndex = 0;
//   }
function load() {
      this.shuffledTrainIndex = 0;
    this.shuffledTestIndex = 0;
    // Make a request for the MNIST sprited image.
    const img = new Image();
    const canvas = document.createElement('canvas');
    const ctx = canvas.getContext('2d');
    const imgRequest = new Promise((resolve, reject) => {
      img.crossOrigin = '';
      img.onload = () => {
        img.width = img.naturalWidth;
        img.height = img.naturalHeight;

        const datasetBytesBuffer =
            new ArrayBuffer(NUM_DATASET_ELEMENTS * IMAGE_SIZE * 4);

        const chunkSize = 5000;
        canvas.width = img.width;
        canvas.height = chunkSize;

        for (let i = 0; i < NUM_DATASET_ELEMENTS / chunkSize; i++) {
          const datasetBytesView = new Float32Array(
              datasetBytesBuffer, i * IMAGE_SIZE * chunkSize * 4,
              IMAGE_SIZE * chunkSize);
          ctx.drawImage(
              img, 0, i * chunkSize, img.width, chunkSize, 0, 0, img.width,
              chunkSize);

          const imageData = ctx.getImageData(0, 0, canvas.width, canvas.height);

          for (let j = 0; j < imageData.data.length / 4; j++) {
            // All channels hold an equal value since the image is grayscale, so
            // just read the red channel.
            datasetBytesView[j] = imageData.data[j * 4] / 255;
          }
        }
        this.datasetImages = new Float32Array(datasetBytesBuffer);

        resolve();
      };
      img.src = MNIST_IMAGES_SPRITE_PATH;
    });

    const labelsRequest = fetch(MNIST_LABELS_PATH);
    const [imgResponse, labelsResponse] =
        Promise.all([imgRequest, labelsRequest]);

    this.datasetLabels = new Uint8Array(labelsResponse.arrayBuffer());

    // Create shuffled indices into the train/test set for when we select a
    // random dataset element for training / validation.
    this.trainIndices = tf.util.createShuffledIndices(NUM_TRAIN_ELEMENTS);
    this.testIndices = tf.util.createShuffledIndices(NUM_TEST_ELEMENTS);

    // Slice the the images and labels into train and test sets.
    this.trainImages =
        this.datasetImages.slice(0, IMAGE_SIZE * NUM_TRAIN_ELEMENTS);
    this.testImages = this.datasetImages.slice(IMAGE_SIZE * NUM_TRAIN_ELEMENTS);
    this.trainLabels =
        this.datasetLabels.slice(0, NUM_CLASSES * NUM_TRAIN_ELEMENTS);
    this.testLabels =
        this.datasetLabels.slice(NUM_CLASSES * NUM_TRAIN_ELEMENTS);
  }

 function nextTrainBatch(batchSize) {
    return this.nextBatch(
        batchSize, [this.trainImages, this.trainLabels], () => {
          this.shuffledTrainIndex =
              (this.shuffledTrainIndex + 1) % this.trainIndices.length;
          return this.trainIndices[this.shuffledTrainIndex];
        });
  }

 function nextTestBatch(batchSize) {
    return this.nextBatch(batchSize, [this.testImages, this.testLabels], () => {
      this.shuffledTestIndex =
          (this.shuffledTestIndex + 1) % this.testIndices.length;
      return this.testIndices[this.shuffledTestIndex];
    });
  }

 function nextBatch(batchSize, data, index) {
    const batchImagesArray = new Float32Array(batchSize * IMAGE_SIZE);
    const batchLabelsArray = new Uint8Array(batchSize * NUM_CLASSES);

    for (let i = 0; i < batchSize; i++) {
      const idx = index();

      const image =
          data[0].slice(idx * IMAGE_SIZE, idx * IMAGE_SIZE + IMAGE_SIZE);
      batchImagesArray.set(image, i * IMAGE_SIZE);

      const label =
          data[1].slice(idx * NUM_CLASSES, idx * NUM_CLASSES + NUM_CLASSES);
      batchLabelsArray.set(label, i * NUM_CLASSES);
    }

    const xs = tf.tensor2d(batchImagesArray, [batchSize, IMAGE_SIZE]);
    const labels = tf.tensor2d(batchLabelsArray, [batchSize, NUM_CLASSES]);

    return {xs, labels};
  }


// TFJS tutorial stuff

function showExamples(data) {
  // Create a container in the visor
  const surface =
    tfvis.visor().surface({ name: 'Input Data Examples', tab: 'Input Data'});  

  // Get the examples
  const examples = data.nextTestBatch(20);
  const numExamples = examples.xs.shape[0];
  
  // Create a canvas element to render each example
  for (let i = 0; i < numExamples; i++) {
    const imageTensor = tf.tidy(() => {
      // Reshape the image to 28x28 px
      return examples.xs
        .slice([i, 0], [1, examples.xs.shape[1]])
        .reshape([28, 28, 1]);
    });
    
    const canvas = document.createElement('canvas');
    canvas.width = 28;
    canvas.height = 28;
    canvas.style = 'margin: 4px;';
    tf.browser.toPixels(imageTensor, canvas);
    surface.drawArea.appendChild(canvas);

    imageTensor.dispose();
  }
}

function run() {  
  const data = load();
  data.load();
  showExamples(data);
}

document.addEventListener('DOMContentLoaded', run);