How can I prevent the CNN from classifying a new input into one of the existing labels (it was trained with) when the input has a new different label?

Question

I'm trying to perform image classification with a CNN. In my case, the inputs are the covers of 9 books, so there are 9 labels. I am using TensorFlow's Keras.

If I pass a new input (that has a label different than one of the 9 labels the CNN was trained with), it will be classified as one of the 9 books, even though it's not a book (but it's e.g. a wall, sofa, house, etc.). I want to avoid this. I want the model to first classify whether there is a book in the image and then classify the book in 9 classes. How could I achieve this?

score 3 · Accepted Answer · answered Dec 12 '18 at 19:10

You can introduce another class to your network - "not a book". After that, you will need to add new data to your dataset, random images that do not contain books to classify and train your network on that data. So when your network won't see a book it will output high probability for "not a book" class, if an image with a book will be shown to the network probability of the "not a book" class should be low.

How can I prevent the CNN from classifying a new input into one of the existing labels (it was trained with) when the input has a new different label?

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