ML / Tensorflow beginner.
Can any of these already-trained models be loaded on tfjs and re-trained there, then exported to Downloads or is Tensorflow python the only way to go?
I see this process is well described and documented in this tutorial for Tensorflow Python but unfortunately I can't find any documentation/tutorial to re-train an object detection model on the browser with tfjs (image classification yes, object detection no).
I see how I could load the coco-ssd model using npm, then probably even trigger saving it to downloads, but what about:
- config file (need to modify it because I want to have only one class, not 90)
- annotated images (both .jpg, .xml and .csv)
- labels.pbtxt
- .record files
Is there any way to go through the process of retraining an ssd model such as ssd_inception_v2_coco and I'm not hitting the right google keywords or is it just not possible in the current state of the framework?
You can use transfer learning by using coco-ssd model as a feature extractor. An example of transfer-learning can be seen here.
Here is a model which extracts features using a features extractor as an input for a new sequential model.
const loadModel = async () => {
const loadedModel = await tf.loadModel(MODEL_URL)
console.log(loadedModel)
// take whatever layer except last output
loadedModel.layers.forEach(layer => console.log(layer.name))
const layer = loadedModel.getLayer(LAYER_NAME)
return tf.model({ inputs: loadedModel.inputs, outputs: layer.output });
}
loadModel().then(featureExtractor => {
model = tf.sequential({
layers: [
// Flattens the input to a vector so we can use it in a dense layer. While
// technically a layer, this only performs a reshape (and has no training
// parameters).
// slice so as not to take the batch size
tf.layers.flatten(
{ inputShape: featureExtractor.outputs[0].shape.slice(1) }),
// add all the layers of the model to train
tf.layers.dense({
units: UNITS,
activation: 'relu',
kernelInitializer: 'varianceScaling',
useBias: true
}),
// Last Layer. The number of units of the last layer should correspond
// to the number of classes to predict.
tf.layers.dense({
units: NUM_CLASSES,
kernelInitializer: 'varianceScaling',
useBias: false,
activation: 'softmax'
})
]
});
})
To detect a single object out of the 90 classes of coco-ssd, one could simply use a conditional test on the prediction of coco-ssd.
const image = document.getElementById(id)
cocoSsd.load()
.then(model => model.detect(image))
.then(prediction => {
if (prediction.class === OBJECT_DETECTED) {
// display it the bbox to the user}
})
If the class does not exist in coco-ssd, then one needs to builds a detector.