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/**
* @license
* Copyright 2018 Google LLC. All Rights Reserved.
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
* =============================================================================
*/
import * as tf from '@tensorflow/tfjs';
import {IMAGENET_CLASSES} from './imagenet_classes';
const IMAGE_SIZE = 224;
export type MobileNetVersion = 1;
export type MobileNetAlpha = 0.25|0.50|0.75|1.0;
const EMBEDDING_NODES: {[version: string]: string} = {
'1.00': 'module_apply_default/MobilenetV1/Logits/global_pool',
'2.00': 'module_apply_default/MobilenetV2/Logits/AvgPool'
};
const MODEL_INFO: {[version: string]: {[alpha: string]: string}} = {
'1.00': {
'0.25':
'https://tfhub.dev/google/imagenet/mobilenet_v1_025_224/classification/1',
'0.50':
'https://tfhub.dev/google/imagenet/mobilenet_v1_050_224/classification/1',
'0.75':
'https://tfhub.dev/google/imagenet/mobilenet_v1_075_224/classification/1',
'1.00':
'https://tfhub.dev/google/imagenet/mobilenet_v1_100_224/classification/1'
},
'2.00': {
'0.50':
'https://tfhub.dev/google/imagenet/mobilenet_v2_050_224/classification/2',
'0.75':
'https://tfhub.dev/google/imagenet/mobilenet_v2_075_224/classification/2',
'1.00':
'https://tfhub.dev/google/imagenet/mobilenet_v2_100_224/classification/2'
}
};
export async function load(
version: MobileNetVersion = 1, alpha: MobileNetAlpha = 1.0) {
if (tf == null) {
throw new Error(
`Cannot find TensorFlow.js. If you are using a <script> tag, please ` +
`also include @tensorflow/tfjs on the page before using this model.`);
}
const versionStr = version.toFixed(2);
const alphaStr = alpha.toFixed(2);
if (!(versionStr in MODEL_INFO)) {
throw new Error(
`Invalid version of MobileNet. Valid versions are: ` +
`${Object.keys(MODEL_INFO)}`);
}
if (!(alphaStr in MODEL_INFO[versionStr])) {
throw new Error(
`MobileNet constructed with invalid alpha ${alpha}. Valid ` +
`multipliers for this version are: ` +
`${Object.keys(MODEL_INFO[versionStr])}.`);
}
const mobilenet = new MobileNet(versionStr, alphaStr);
await mobilenet.load();
return mobilenet;
}
export class MobileNet {
model: tf.GraphModel;
private normalizationOffset: tf.Scalar;
constructor(public version: string, public alpha: string) {
this.normalizationOffset = tf.scalar(127.5);
}
async load() {
const url = MODEL_INFO[this.version][this.alpha];
this.model = await tf.loadGraphModel(url, {fromTFHub: true});
// Warmup the model.
const result = tf.tidy(
() => this.model.predict(tf.zeros(
[1, IMAGE_SIZE, IMAGE_SIZE, 3]))) as tf.Tensor;
await result.data();
result.dispose();
}
/**
* Computes the logits (or the embedding) for the provided image.
*
* @param img The image to classify. Can be a tensor or a DOM element image,
* video, or canvas.
* @param embedding If true, it returns the embedding. Otherwise it returns
* the 1000-dim logits.
*/
infer(
img: tf.Tensor|ImageData|HTMLImageElement|HTMLCanvasElement|
HTMLVideoElement,
embedding = false): tf.Tensor {
return tf.tidy(() => {
if (!(img instanceof tf.Tensor)) {
img = tf.browser.fromPixels(img);
}
// Normalize the image from [0, 255] to [-1, 1].
const normalized = img.toFloat()
.sub(this.normalizationOffset)
.div(this.normalizationOffset) as tf.Tensor3D;
// Resize the image to
let resized = normalized;
if (img.shape[0] !== IMAGE_SIZE || img.shape[1] !== IMAGE_SIZE) {
const alignCorners = true;
resized = tf.image.resizeBilinear(
normalized, [IMAGE_SIZE, IMAGE_SIZE], alignCorners);
}
// Reshape so we can pass it to predict.
const batched = resized.reshape([-1, IMAGE_SIZE, IMAGE_SIZE, 3]);
let result: tf.Tensor2D;
if (embedding) {
const embeddingName = EMBEDDING_NODES[this.version];
const internal =
this.model.execute(batched, embeddingName) as tf.Tensor4D;
result = internal.squeeze([1, 2]);
} else {
const logits1001 = this.model.predict(batched) as tf.Tensor2D;
// Remove the very first logit (background noise).
result = logits1001.slice([0, 1], [-1, 1000]);
}
return result;
});
}
/**
* Classifies an image from the 1000 ImageNet classes returning a map of
* the most likely class names to their probability.
*
* @param img The image to classify. Can be a tensor or a DOM element image,
* video, or canvas.
* @param topk How many top values to use. Defaults to 3.
*/
async classify(
img: tf.Tensor3D|ImageData|HTMLImageElement|HTMLCanvasElement|
HTMLVideoElement,
topk = 3): Promise<Array<{className: string, probability: number}>> {
const logits = this.infer(img) as tf.Tensor2D;
const classes = await getTopKClasses(logits, topk);
logits.dispose();
return classes;
}
}
async function getTopKClasses(logits: tf.Tensor2D, topK: number):
Promise<Array<{className: string, probability: number}>> {
const softmax = logits.softmax();
const values = await softmax.data();
softmax.dispose();
const valuesAndIndices = [];
for (let i = 0; i < values.length; i++) {
valuesAndIndices.push({value: values[i], index: i});
}
valuesAndIndices.sort((a, b) => {
return b.value - a.value;
});
const topkValues = new Float32Array(topK);
const topkIndices = new Int32Array(topK);
for (let i = 0; i < topK; i++) {
topkValues[i] = valuesAndIndices[i].value;
topkIndices[i] = valuesAndIndices[i].index;
}
const topClassesAndProbs = [];
for (let i = 0; i < topkIndices.length; i++) {
topClassesAndProbs.push({
className: IMAGENET_CLASSES[topkIndices[i]],
probability: topkValues[i]
});
}
return topClassesAndProbs;
}
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