Relation between CNN and gabor filter

Question

I am learning to use gabor filters to extract orientation and scale related features from images. On the other hand, Convolution Neural Network can also extract features including orientation and scale, is there any evidence that filters in CNN performs a similar function as gabor filters? Or pros and cons of both of them.

Answer 1

In my personal experience, in a traditional deep learning architecture (such as AlexNet) , when the layers near the beginning are visualized, they resemble gabor filters a lot.

Take this visualization of the first two layers of a pretrained AlexNet (taken from Andrej Karpathy's cs231n.github.io ). Some of the learnt filters look exactly like the Gabor Filters. So yes, there is evidence that CNN works (partly) the same way as Gabor Filters.

One possible explanation is that since the layers towards the beginning of a deep CNN are used to extract low level features (such as changes in texture), they perform the same functions as Gabor Filters. Features such as those detecting changes in frequency are so fundamental that they are present irrespective of the type of dataset the model is trained on. (Part of the reason why transfer learning is possible) .

But if you have more more data, you could possibly make a deep CNN learn much more high-level features than Gabor Filters, which might be more useful for the task you're extracting these features for (such as classification). I hope this provides some clarification.