An example of step image frames from a non-PD control subject. (a) Step image frames from a non-PD control subject. The top panel is the original sequential walking image frames with 240 × 320 pixels. The bottom panel is the trimmed 64 × 64 pixels binary silhouettes of the top image frames. (b) The magnitudes of the associated sequential primary KPCA components. For simplicity, the primary KPCA component is denoted as 1st
KPC. The green dots indicate the magnitudes of the sequential 1st
KPCs. (c) The power spectrum of (b) using a 2048-point DFT and rectangular window with a length, L, of 64 points.