Recently I recorded a video explaining in a very simple way how style transfer works in a convolutional neural network (VGG16) based on the incredibly well-written paper by Gatys et al [1]. I also implemented it in an extremely concise and simple way (around than 150 lines with comments).
Original Image
Combinations
The code is provided in the Source code section.
References
1. Gatys LA, Ecker AS and Bethge M. 2016. Image Style Transfer Using Convolutional Neural Network.