Function predict

mobilenet/index.js:61–95

* Given an image element, makes a prediction through mobilenet returning the * probabilities of the top K classes.

(imgElement)

 * probabilities of the top K classes.
 */
async function predict(imgElement) {
  status('Predicting...');

  // The first start time includes the time it takes to extract the image
  // from the HTML and preprocess it, in additon to the predict() call.
  const startTime1 = performance.now();
  // The second start time excludes the extraction and preprocessing and
  // includes only the predict() call.
  let startTime2;
  const logits = tf.tidy(() => {
    // tf.browser.fromPixels() returns a Tensor from an image element.
    const img = tf.cast(tf.browser.fromPixels(imgElement), 'float32');

    const offset = tf.scalar(127.5);
    // Normalize the image from [0, 255] to [-1, 1].
    const normalized = img.sub(offset).div(offset);

    // Reshape to a single-element batch so we can pass it to predict.
    const batched = normalized.reshape([1, IMAGE_SIZE, IMAGE_SIZE, 3]);

    startTime2 = performance.now();
    // Make a prediction through mobilenet.
    return mobilenet.predict(batched);
  });

  // Convert logits to probabilities and class names.
  const classes = await getTopKClasses(logits, TOPK_PREDICTIONS);
  const totalTime1 = performance.now() - startTime1;
  const totalTime2 = performance.now() - startTime2;
  status(`Done in ${Math.floor(totalTime1)} ms ` +
      `(not including preprocessing: ${Math.floor(totalTime2)} ms)`);

  // Show the classes in the DOM.
  showResults(imgElement, classes);
}

/**
 * Computes the probabilities of the topK classes given logits by computing