added darknet reference and darknet tiny classifiers (#201)

* added darknet reference and darknet tiny classifiers

* fixed linting stuff

* edits..

* edits2.0

* clean comments

Author: hiddentn

src/ImageClassifier/darknet.js

@@ -0,0 +1,118 @@
+// Copyright (c) 2018 ml5
+//
+// This software is released under the MIT License.
+// https://opensource.org/licenses/MIT
+
+import * as tf from '@tensorflow/tfjs';
+import IMAGENET_CLASSES_DARKNET from '../utils/IMAGENET_CLASSES_DARKNET';
+
+const DEFAULTS = {
+  DARKNET_URL: 'https://rawgit.com/ml5js/ml5-data-and-models/master/models/darknetclassifier/darknetreference/model.json',
+  DARKNET_TINY_URL: 'https://rawgit.com/ml5js/ml5-data-and-models/master/models/darknetclassifier/darknettiny/model.json',
+  IMAGE_SIZE_DARKNET: 256,
+  IMAGE_SIZE_DARKNET_TINY: 224,
+};
+
+async function getTopKClasses(logits, topK) {
+  const values = await logits.data();
+  const valuesAndIndices = [];
+  for (let i = 0; i < values.length; i += 1) {
+    valuesAndIndices.push({
+      value: values[i],
+      index: i,
+    });
+  }
+  valuesAndIndices.sort((a, b) => b.value - a.value);
+
+  const topkValues = new Float32Array(topK);
+  const topkIndices = new Int32Array(topK);
+  for (let i = 0; i < topK; i += 1) {
+    topkValues[i] = valuesAndIndices[i].value;
+    topkIndices[i] = valuesAndIndices[i].index;
+  }
+
+  const topClassesAndProbs = [];
+  for (let i = 0; i < topkIndices.length; i += 1) {
+    topClassesAndProbs.push({
+      className: IMAGENET_CLASSES_DARKNET[topkIndices[i]],
+      probability: topkValues[i],
+    });
+  }
+  return topClassesAndProbs;
+}
+
+function preProcess(img, size) {
+  let image;
+  if (!(img instanceof tf.Tensor)) {
+    if (img instanceof HTMLImageElement || img instanceof HTMLVideoElement) {
+      image = tf.fromPixels(img);
+    } else if (typeof img === 'object' && (img.elt instanceof HTMLImageElement || img.elt instanceof HTMLVideoElement)) {
+      image = tf.fromPixels(img.elt); // Handle p5.js image and video.
+    }
+  } else {
+    image = img;
+  }
+  const normalized = image.toFloat().div(tf.scalar(255));
+  let resized = normalized;
+  if (normalized.shape[0] !== size || normalized.shape[1] !== size) {
+    const alignCorners = true;
+    resized = tf.image.resizeBilinear(normalized, [size, size], alignCorners);
+  }
+  const batched = resized.reshape([1, size, size, 3]);
+  return batched;
+}
+
+export class Darknet {
+  constructor(version) {
+    this.version = version;
+    switch (this.version) {
+      case 'reference':
+        this.imgSize = DEFAULTS.IMAGE_SIZE_DARKNET;
+        break;
+      case 'tiny':
+        this.imgSize = DEFAULTS.IMAGE_SIZE_DARKNET_TINY;
+        break;
+      default:
+        break;
+    }
+  }
+
+  async load() {
+    switch (this.version) {
+      case 'reference':
+        this.model = await tf.loadModel(DEFAULTS.DARKNET_URL);
+        break;
+      case 'tiny':
+        this.model = await tf.loadModel(DEFAULTS.DARKNET_TINY_URL);
+        break;
+      default:
+        break;
+    }
+
+    // Warmup the model.
+    const result = tf.tidy(() => this.model.predict(tf.zeros([1, this.imgSize, this.imgSize, 3])));
+    await result.data();
+    result.dispose();
+  }
+
+  async classify(img, topk = 3) {
+    const logits = tf.tidy(() => {
+      const imgData = preProcess(img, this.imgSize);
+      const predictions = this.model.predict(imgData);
+      return tf.softmax(predictions);
+    });
+    const classes = await getTopKClasses(logits, topk);
+    logits.dispose();
+    return classes;
+  }
+}
+
+export async function load(version) {
+  if (version !== 'reference' && version !== 'tiny') {
+    throw new Error('Please select a version: darknet-reference or darknet-tiny');
+  }
+
+  const darknet = new Darknet(version);
+  await darknet.load();
+  return darknet;
+}

src/ImageClassifier/index.js

@@ -9,6 +9,7 @@ Image Classifier using pre-trained networks
 
 import * as tf from '@tensorflow/tfjs';
 import * as mobilenet from '@tensorflow-models/mobilenet';
+import * as darknet from './darknet';
 import callCallback from '../utils/callcallback';
 
 const DEFAULTS = {
@@ -23,14 +24,24 @@ class ImageClassifier {
   constructor(modelName, video, options, callback) {
     this.modelName = modelName;
     this.video = video;
-    this.version = options.version || DEFAULTS[this.modelName].version;
-    this.alpha = options.alpha || DEFAULTS[this.modelName].alpha;
-    this.topk = options.topk || DEFAULTS[this.modelName].topk;
     this.model = null;
-    if (this.modelName === 'mobilenet') {
-      this.modelToUse = mobilenet;
-    } else {
-      this.modelToUse = null;
+    switch (this.modelName) {
+      case 'mobilenet':
+        this.modelToUse = mobilenet;
+        this.version = options.version || DEFAULTS.mobilenet.version;
+        this.alpha = options.alpha || DEFAULTS.mobilenet.alpha;
+        this.topk = options.topk || DEFAULTS.mobilenet.topk;
+        break;
+      case 'darknet':
+        this.version = 'reference'; // this a 28mb model
+        this.modelToUse = darknet;
+        break;
+      case 'darknet-tiny':
+        this.version = 'tiny'; // this a 4mb model
+        this.modelToUse = darknet;
+        break;
+      default:
+        this.modelToUse = null;
     }
     // Load the model
     this.ready = callCallback(this.loadModel(), callback);