DOC-tf

Implementation of Deep Occlusion Estimation in Tensorflow along with associated border ownership experiments

The program is written in Python 3 using Tensorflow. For more details about the border ownership experiments, please see the following reference:

@inproceedings{Hu_etal19CISS,
    Title                    = {Figure-ground representation in deep neural networks},
    Author                   = {Hu, Brian and Khan, Salman and Niebur, Ernst and Tripp, Bryan},
    Booktitle                = {IEEE CISS-2019 53rd Annual Conference on Information Sciences and Systems},
    Year                     = {2019},
    Address                  = {Baltimore, MD},
    Organization             = {IEEE Information Theory Society},
    Pages                    = {1-6},
    Doi                      = {10.1109/CISS.2019.8693039}
}

DOC: Deep OCclusion Estimation From a Single Image

This repository is based on the Caffe model found here. The goal was to convert this model to Tensorflow for further network dissection and experimentation.

Model Conversion

The first step is to get the Caffe model weights and prototxt definition files. They can be found here. I first tried converting the model from Caffe to Tensorflow using the caffe-tensorflow tool. Unfortunately, many layers (including Crop and Deconvolution) are not properly implemented. I then came across the MMdnn tool from Microsoft, which allows for conversion of models between different frameworks (e.g. Tensorflow, Caffe, Pytorch, etc.) I adapted the code there after running into the following issues (my fork of the code is here):

1. I didn't want to install Caffe just to do the conversion, so I used a pure protobuf implementation. You have to uncomment out the corresponding lines in the mmdnn/conversion/caffe/resolver.py file to fallback on a protobuf implementation.

2. The converter expects the crop layer to have an output shape, which is missing from the .prototxt file. I just commented out the crop layers in the .prototxt file.

3. The converter expects the deconvolution layer to have a dilation parameter, which is missing from the .prototxt file. I just set it to 1 by default in the mmdnn/conversion/caffe/shape.py file (similar to other layers).

4. There was also an issue with computing the max size of the output layers, since the output prediction is a zero-dim numpy scalar. I edited mmdnn/conversion/caffe/graph.py to check for zero-dim numpy scalars.

Following these steps resulted in a numpy (.npy) file containing the network weights, and a python (.py) file containing the model graph definition. These are denoted doc.npy and doc.py for the orientation estimation network and hed.npy and hed.py for the boundary detection network, respectively. This was tested on Python 2.7 with Tensorflow 1.8.

Tensorflow Graph

The final output Tensorflow graph (*.py file) had a few extra "L"s in the shape components, which I had to manually delete before the python file could be run without errors. I also had to go in and change the shapes of some of the layers to allow for arbitrary input image sizes (it was hard-coded to 500x500 before). The main changes were making the input layer accept arbitrary dimension images and using a padding size of 1 instead of 35. Also, in the deconvolution layers, I checked for the input image size dynamically and used "SAME" padding instead of "VALID" padding.

Example Inference

You can pass an arbitrary image to the model and get the model's edge and/or orientation outputs. For example, to get the boundary detection output:

# Boundary detection on image 41004
python tensorflow_inference.py -n hed -w model/hed.npy -i img/41004.jpg

# Orientation estimation on image 108041
python tensorflow_inference.py -n doc -w model/doc.npy -i img/108041.jpg

Example Output

Original	Edge	Orientation

This was tested on Python 3.6 with Tensorflow 1.8. You will also need to install pillow (for image loading) and matplotlib (for plotting results).