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neural image analogies

Image of arch Image of Trump Image of Sugar Steve

This is basically an implementation of this "Image Analogies" paper http://www.mrl.nyu.edu/projects/image-analogies/index.html In our case, we use feature maps from VGG16. The patch matching and blending is done with a method described in "Combining Markov Random Fields and Convolutional Neural Networks for Image Synthesis" http://arxiv.org/abs/1601.04589 Effects similar to that paper can be achieved by turning off the analogy loss (or leave it on!) and turning on the B/B' content weighting via the --b-content-w parameter.

The initial code was adapted from the Keras "neural style transfer" example.

The example arch images are from the "Image Analogies" website at http://www.mrl.nyu.edu/projects/image-analogies/tbn.html They have some other good examples from their own implementation which are worth a look. Their paper discusses the various applications of image analogies so you might want to take a look for inspiration.

Installation

You'll want to run this on a GPU. http://deeplearning.net/software/theano/tutorial/using_gpu.html

To install via virtualenv run the following commands.

virtualenv venv
source venv/bin/activate
pip install -r requirements.txt

If you have trouble with the above method, follow these directions to Install latest keras and theano (requires theano, no tensorflow atm).

Before running this script, download the weights for the VGG16 model at: https://drive.google.com/file/d/0Bz7KyqmuGsilT0J5dmRCM0ROVHc/view?usp=sharing (source: https://gist.github.com/baraldilorenzo/07d7802847aaad0a35d3) and make sure the variable weights_path in this script matches the location of the file or use the --vgg-weights parameter

Example script usage: python image_analogy.py path_to_A path_to_A_prime path_to_B prefix_for_B_prime

e.g.:

python image_analogy.py images/arch-mask.jpg images/arch.jpg images/arch-newmask.jpg out/arch

Currently, A and A' must be the same size, the same holds for B and B'. Output size is the same as Image B, unless specified otherwise.

It's too slow

If you don't have a beefy GPU or just want to crank out a styled image, you have a few options to play with. They all trade detail for speed/memory.

  • set --patch-size=1 or 2 to consider smaller feature patches (default is 3)
  • set --mrf-w=0 to skip optimization of local coherence
  • use fewer feature layers by setting --mrf-layers=conv4_1 and/or --analogy-layers=conv4_1 (or other layers) which will consider half as many feature layers.
  • enable Theano openmp threading by using env variables THEANO_FLAGS='openmp=1,openmp_elemwise_minsize=<min_tensor_size>' OMP_NUM_THREADS=<cpu_num>. You can read more about multi-core support here.

Parameters

  • --width Sets image output max width
  • --height Sets image output max height
  • --scales Run at N different scales
  • --iters Number of iterations per scale
  • --min-scale Smallest scale to iterate
  • --mrf-w Weight for MRF loss between A' and B'
  • --analogy-w Weight for analogy loss
  • --b-content-w Weight for content loss between B and B'
  • --tv-w Weight for total variation loss
  • --vgg-weights Path to VGG16 weights
  • --a-scale-mode Method of scaling A and A' relative to B
    • 'match': force A to be the same size as B regardless of aspect ratio (current default for backwards compatibility)
    • 'ratio': apply scale imposed by width/height params on B to A
    • 'none': leave A/A' alone
  • --a-scale Additional scale factor for A and A'
  • --pool-mode Pooling style used by VGG
    • 'avg': average pooling - generally smoother results
    • 'max': max pooling - more noisy but maybe that's what you want (original default)
  • --contrast adjust the contrast of the output by removing the bottom x percentile and scaling by the (100 - x)th percentile. Defaults to 0.02
  • --output-full Output all intermediate images at full size regardless of actual scale
  • --analogy-layers Comma-separated list of layer names to be used for the analogy loss (default: "conv3_1,conv_4_1")
  • --mrf-layers Comma-separated list of layer names to be used for the MRF loss (default: "conv3_1,conv_4_1")
  • --content-layers Comma-separated list of layer names to be used for the content loss (default: "conv3_1,conv_4_1")
  • --patch-size Patch size used for matching (default: 3)
  • --use-full-analogy match on all of the analogy patches, instead of combining them into one image (slower/more memory but maybe more accurate)

The analogy loss is the amount of influence of B -> A -> A' -> B'. It's a structure-preserving mapping of Image B into A' via A.

The MRF loss (or "local coherence") is the influence of B' -> A' -> B'. In the parlance of style transfer, this is the style loss which gives texture to the image.

The B/B' content loss is set to 0.0 by default. You can get effects similar to CNNMRF by turning this up and setting analogy weight to zero. Or leave the analogy loss on for some extra style guidance.

If you'd like to only visualize the analogy target to see what's happening, set the MRF and content loss to zero: --mrf-w=0 --content-w=0 This is also much faster as MRF loss is the slowest part of the algorithm.