Algorithm 1 Iterative Seeding

Require: Reference gray-scale image ${\mathbf{y}}_0$, function TranslateIntensity returning intensities of visible light given the current near-infrared intensity and the current visible-light intensity     ${\mathbf{x}}_T\sim \mathcal{N}(0,\mathbf{I})$     for  $t=T,\cdots ,1$  do         ${\mathbf{y}}_{t-1}\sim q\left({\mathbf{y}}_{t-1}\right|{\mathbf{y}}_0)$         ${\tilde{\mathbf{x}}}_{t-1}\sim p_{\theta }\left({\tilde{\mathbf{x}}}_{t-1}\right|{\mathbf{x}}_t)$         ${\mathbf{y}}_{t-1}^I,{\mathbf{y}}_{t-1}^C=$ DecoupleIntensity(${\mathbf{y}}_{t-1}$)         ${\tilde{\mathbf{x}}}_{t-1}^I,{\tilde{\mathbf{x}}}_{t-1}^C=$ DecoupleIntensity(${\tilde{\mathbf{x}}}_{t-1}$)         ${\mathbf{x}}_{t-1}^I=$ TranslateIntensity(${\mathbf{y}}_{t-1}^I,{\tilde{\mathbf{x}}}_{t-1}^I$)         ${\mathbf{x}}_{t-1}=$ CoupleIntensity(${\mathbf{x}}_{t-1}^I$,${\tilde{\mathbf{x}}}_{t-1}^C$)      return  ${\mathbf{x}}_0$