Fig. 2

(a): Illustration of a cycle-consistent generative adversarial network (Cycle-GAN) – dashed squares in purple and cyan denote images from (or in the style of) device A (source domain) and device B (target domain), respectively; G represents Generator 1 [source image → target image], and F represents Generator 2 [target image → source image]; (b): schematic map of hypothetical feature distributions of five devices; the actual feature maps are presumably more overlying, but for illustrative purposes, they are located more distantly in this illustration; (c): conventional direct cross-device translations diagram; (d): indirect cross-device translations using an intermediate domain as the bridge; Note: every two generators in one Cycle-GAN (i.e., forward and backward) are denoted by a red bidirectional arrow