A Semi-Supervised Image-to-Image Translation Framework for SAR–Optical Image Matching

Synthetic aperture radar (SAR) and optical image matching aims to acquire correspondences from a certain pair of SAR and optical images. Recent advances in the image-to-image translation provided a way to simplify the SAR–optical image matching into the SAR–SAR or optical–optical image matchings. The existing image-to-image translations mainly focus on supervised or unsupervised learning. However, gathering sufficient amounts of aligned training data for supervised learning is challenging, while unsupervised learning cannot guarantee enough correct correspondences. In this work, we investigate the applicability of semi-supervised image-to-image translation for SAR–optical image matching such that both aligned and unaligned SAR–optical images could be used. To this end, we combine the benefits of both supervised and unsupervised well-known image-to-image translation methods, i.e., Pix2pix and CycleGAN, and propose a simple yet effective semi-supervised image-to-image translation framework. Through extensive experimental comparisons to the baseline methods, we verify the effectiveness of the proposed framework in both semi-supervised and fully supervised settings. Our codes are available at
https://github.com/WenliangDu/Semi-I2I
.