Algorithm 1: One-Dimensional PPG Signal to Two-Dimensional Scalogram via CWT

Input:  $\mathrm{Preprocessed} \mathrm{and} \mathrm{normalized} \mathrm{PPG} \mathrm{signal} x\left(t\right)$

Output:$\mathrm{Two}-\mathrm{dimensional} \mathrm{time}-\mathrm{frequency} \mathrm{map} \left(\mathrm{scalogram}\right) X_w\left(u,v\right)$

Step 1: Choose mother wavelet ψ(t) = Morlet

$\mathrm{Step} 2: \mathrm{For} \mathrm{each} \mathrm{scale} u$$\mathrm{and} \mathrm{time} \mathrm{shift} v$:

$\mathrm{Compute} X_w\left(u,v\right)={\displaystyle {\int }_{-\infty }^{\infty }x\left(t\right)}{\phi }_{u,v}\left(t\right)dt$

$\mathrm{Step} 3: \mathrm{Take} \mathrm{absolute} \mathrm{value}: S(u,v)=\left|X_w\left(u,v\right)\right|$

$\mathrm{Step} 4: \mathrm{Resize} S(u,v)$ to fixed dimension (224 × 224)