K.gradients(loss, input_img)[0] return “None”. (Keras CNN visualization with tensorflow backend)

Question

I have CNN models trained using Keras with Tensorflow backend. And I want to visualize my CNN filters with this tutorial: https://blog.keras.io/how-convolutional-neural-networks

Answer 1

Below, it's my example. Hope to help someone.

gradient = keras.backend.gradients(model.output, model.input)[2]

iterate = keras.backend.function(model.input, [gradient])

grad = iterate([patches, depthes, poses])

[patches, depthes, poses] is my model.input