TableTrainNet

A simple project for training and testing table recognition in documents.

This project was developed to make a neural network which recognizes tables inside documents. I needed an "intelligent" ocr for work, which could automatically recognize tables to treat them separately.

General overview

The project uses the pre-trained neural network offered by Tensorflow. In addition, a config file was used, according to the choosen pre-trained model, to train with object detections tensorflow API

The datasets was taken from:

• ICDAR 2017 POD Competition.
• Not already implemented:
  • UNLV dataset with its own ground truth;
  • Marmot Dataset

Required libraries

Before we go on make sure you have everything installed to be able to use the project:

• Python 3
• Tensorflow (tested on r1.8)
• Its object-detection API (remember to install COCO API. If you are on Windows see at the bottom of the readme)
• Pillow
• opencv-python
• pandas
• pyprind (useful for process bars)

Project pipeline

The project is made up of different parts that acts together as a pipeline.

Take confidence with costants

I have prepared two "costants" files: dataset_costants.py and inference_constants.py. The first contains all those costants that are useful to use to create dataset, the second to make inference with the frozen graph. If you just want to run the project you should modify only those two files.

Transform the images from RGB to single-channel 8-bit grayscale jpeg images

Since colors are not useful for table detection, we can convert all the images in .jpeg 8-bit single channel images. This) transformation is still under testing. Use python dataset/img_to_jpeg.py after setting dataset_costants.py:

• DPI_EXTRACTION: output quality of the images;
• PATH_TO_IMAGES: path/to/datase/images;
• IMAGES_EXTENSION: extension of the extracted images. The only one tested is .jpeg.

Prepare the dataset for Tensorflow

The dataset was take from ICDAR 2017 POD Competition . It comes with a xml notation file with formulas, images and tables per image. Tensorflow instead can build its own TFRecord from csv informations, so we need to convert the xml files into a csv one. Use python dataset/generate_database_csv.py to do this conversion after setting dataset_costants.py:

• TRAIN_CSV_NAME: name for .csv train output file;
• TEST_CSV_NAME: name for .csv test output file;
• TRAIN_CSV_TO_PATH: folder path for TRAIN_CSV_NAME;
• TEST_CSV_TO_PATH: folder path for TEST_CSV_NAME;
• ANNOTATIONS_EXTENSION: extension of annotations. In our case is .xml;
• TRAINING_PERCENTAGE: percentage of images for training
• TEST_PERCENTAGE: percentage of images for testing
• TABLE_DICT: dictionary for data labels. For this project there is no reason to change it;
• MIN_WIDTH_BOX, MIN_HEIGHT_BOX: minimum dimension to consider a box valid; Some networks don't digest well little boxes, so I put this check.

Generate TF records file

csv files and images are ready: now we need to create our TF record file to feed Tensorflow. Use python generate_tf_records.py to create the train and test.record files that we will need later. No need to configure dataset_costants.py

Train the network

Inside trained_models there are some folders. In each one there are two files, a .config and a .txt one. The first contains a tensorflow configuration, that has to be personalized:

• fine_tune_checkpoint: path to the frozen graph from pre-trained tensorflow models networks;
• tf_record_input_reader: path to the train.record and test.record file we created before;
• label_map_path: path to the labels of your dataset.

The latter contains the command to launch from tensorflow/models/research/object-detection and follows this pattern:

python model_main.py \
--pipeline_config_path=path/to/your_config_file.config \
--model_dir=here/we/save/our/model" \ 
--num_train_steps=num_of_iterations \
--alsologtostderr

Other options are inside tensorflow/models/research/object-detection/model_main.py

Prepare frozen graph

When the net has finished the training, you can export a frozen graph to make inference. Tensorflow offers the utility: from tensorflow/models/research/object-detection run:

python export_inference_graph.py \ 
--input_type=image_tensor \
--pipeline_config_path=path/to/automatically/created/pipeline.config \ 
--trained_checkpoint_prefix=path/to/last/model.ckpt-xxx \
--output_directory=path/to/output/dir

Test your graph!

Now that you have your graph you can try it out: Run inference_with_net.py and set inference_costants.py:

• PATHS_TO_TEST_IMAGE: path list to all the test images;
• BMP_IMAGE_TEST_TO_PATH: path to which save test output files;
• PATHS_TO_LABELS: path to .pbtxt label file;
• MAX_NUM_BOXES: max number of boxes to be considered;
• MIN_SCORE: minimum score of boxes to be considered;

Then it will be generated a result image for every combination of:

• PATHS_TO_CKPTS: list path to all frozen graph you want to test;

In addition it will print a "merged" version of the boxes, in which all the best vertically overlapping boxes are merged together to gain accuracy. TEST_SCORES is a list of numbers that tells the program which scores must be merged together.

The procedure is better described in inference_with_net.py.

For every execution a .log file will be produced.

Common issues while installing Tensorflow models

TypeError: can't pickle dict_values objects

This comment will probably solve your problem.

Windows build and python3 support for COCO API dataset

This clone will provide a working source for COCO API in Windows and Python3