This directory includes a miscellaneous collection of useful helper functions.

• image_pool.py implements an image buffer that stores previously generated images. This buffer enables us to update discriminators using a history of generated images rather than the ones produced by the latest generators. The original idea was discussed in this paper. The size of the buffer is controlled by the pool_size option.

• metrics.py contains a metrics object building, which allows dynamic selection of the metrics to calculate (between psnr, ssim and lpips) and the output of the averaging call integrates with the ReduceLROnPlateau optimizer option.

• util.py consists of simple helper functions that are repeatelly used in the code such as mkdirs (create multiple directories), scandir (scan a directory to find defined files), get_root_logger (create or fetch a root logger) and others.

• progress_bar.py a convenient progress bar. Currently only used by the lmdb dataset creation script.