This project includes the code for semantic segmentation of satelite images implemented during the internship at Duke.

Three CNN based segmentation models and some utilities like data reader, segmentation metric, pre/post-processing, etc.

• dataReader: functions of reading image data for deep nets
  • image_reader.py
  • mat_batch_reader
  • matFileDescription.txt
  • patchify.py
• metrics: implementations of segmentation performance metrics
• notebook: notebooks for visualizing experiment results or test functionalities of other functions
• utils: script for image pre/post processing
• FCN: Fully convolutional network modified from the implementation here.
• tensorflow-deeplab-resnet: DeepLab model modified from the implementation here
• UNet-in-Tensorflow: UNet model modified from the implementation here

The project were tested under the

• Tensorflow 1.1.0: FCN and DeepLab model are under TF of python 3.5 and U-Net was tested under TF of python 2.7.
• Numpy 1.12.1
• scipy 0.19.0 Other used modules can be found at the importing part of every script

This example shows a procedure of training a U-Net for building segmentation

1. Data preparation:
   • The original satellite images are of large sizes and can not be feed into U-Net or other CNNs. They are of different pysical resolution (length/pixel) as well. The first step is to unify them into the same resolution using ./utils/unify_image_resolution.py.
   • Use patchify_building_images.py to generated small patches from a pair of RGB image and a binary label image (ground truth). The generated patch pairs will be named as {LargeImageName}_{index}_image.png and {LargeImageName}_{index}_truth.png. Also, a text file, of which each line is the path of color image and truth image pair, is generated.
2. Training: Use train.py to train models.
   • The path of folder containing the generated patches and the text file of the path list from step 1 should be provided to train.py.
   • Hyperparameters for training a CNN is needed as well. More details about needed parameters are in train.py.
   • During training, checkpoints (trained model and meta data for tensorboard) are saved (was set under ./snapshots_building/{experiments_name}) so that it can be used for testing or continuing an interuptted training. You can also use Tensorboard to analysis the training process, like the cost function values.
   • experiments_train.py recursively run train.py with different training parameters.
3. Testing: Use test.py to evaluate trained models.
   • The path of trained model and the large image to be tested on are needed.
   • The large image are divided small patches and their predictions are stitched into a large label image for evaluation. Those patches are overlapped. So each patch is weighted with a 2D Gaussion distribution (same size with the path, higher weight at the center of each patch). The stitched images of weighted patches are normalized with the stitched Gaussion masks.
   • Evaluate the performance using the metric class in seg_metric.py or functions in eval_segm.py.
   • Run experiments_test.py for testing different models on different test data.