In recent years, multi-scale generative adversarial networks (GANs) have been proposed to build generalized image processing models based on single sample. Constraining on the sample size, multi-scale GANs have much difficulty converging to the global optimum, which ultimately leads to limitations in their capabilities. In this paper, we pioneered the introduction of PAC-Bayes generalized bound theory into the training analysis of specific models under different adversarial training methods, which can obtain a non-vacuous upper bound on the generalization error for the specified multi-scale GAN structure. Based on the drastic changes we found of the generalization error bound under different adversarial attacks and different training states, we proposed an adaptive training method which can greatly improve the image manipulation ability of multi-scale GANs. The final experimental results show that our adaptive training method in this paper has greatly contributed to the improvement of the quality of the images generated by multi-scale GANs on several image manipulation tasks. In particular, for the image super-resolution restoration task, the multi-scale GAN model trained by the proposed method achieves a 100% reduction in natural image quality evaluator (NIQE) and a 60% reduction in root mean squared error (RMSE), which is better than many models trained on large-scale datasets.
This paper presents a novel surrogate-based cross-correlation (SBCC) framework to improve the correlation performance between two image signals. The basic idea behind the SBCC is that an optimized surrogate filter/image, supplanting one original image, will produce a more robust and more accurate correlation signal. The cross-correlation estimation of the SBCC is formularized with an objective function composed of surrogate loss and correlation consistency loss. The closed-form solution provides an efficient estimation. To our surprise, the SBCC framework could provide an alternative view to explain a set of generalized cross-correlation (GCC) methods and comprehend the meaning of parameters. With the help of our SBCC framework, we further propose four new specific cross-correlation methods, and provide some suggestions for improving existing GCC methods. A noticeable fact is that the SBCC could enhance the correlation robustness by incorporating other negative context images. Considering the sub-pixel accuracy and robustness requirement of particle image velocimetry (PIV), the contribution of each term in the objective function is investigated with particles' images. Compared with the state-of-the-art baseline methods, the SBCC methods exhibit improved performance (accuracy and robustness) on the synthetic dataset and several challenging real experimental PIV cases.