2 To extract image features, we used a convolutional neural network model trained on 1.2M images of 1000 class ILSVRC 2012 object classification dataset, a subset of ImageNet (Russakovsky et al., 2015).
we used VGG 19-layer CNN architecture and extracted the activations of the penultimate fully connected layer to obtain features for all images in the dataset (Simonyan and Zisserman, 2015).