  Despite significant progress of applying deep learning methods to the field
of content-based image retrieval, there has not been a software library that
covers these methods in a unified manner. In order to fill this gap, we
introduce PyRetri, an open source library for deep learning based unsupervised
image retrieval. The library encapsulates the retrieval process in several
stages and provides functionality that covers various prominent methods for
each stage. The idea underlying its design is to provide a unified platform for
deep learning based image retrieval research, with high usability and
extensibility. To the best of our knowledge, this is the first open-source
library for unsupervised image retrieval by deep learning.
