toTensor.js

  toTensor: function(canvas) {
    return tf.tidy(() => {
      // Convert the ImageData to Tensor
      const image = tf.fromPixels(canvas)

      // The input shape of YOLO is 416x416x3, we need to crop the image
      const size = this.size.width
      const beginX = image.shape[1] / 2 - size / 2
      const beginY = image.shape[0] / 2 - size / 2 
      const cropped = image.slice([beginY, beginX, 0], [size, size, 3])

      // Create a batch of image but with only one image
      const batchImage = cropped.expandDims(0)
      
      // normalize the data
      return batchImage.toFloat().div(tf.scalar(255))
    })
  },