Figure 4.

Motion tracking using contrast-enhanced video images: (A) Top left image: original, raw video image with pixel intensities normalized to minimal and maximal values in entire video (I(x, y) ∈ [0, 1]). Top right image: contrast-enhanced video image used for motion tracking (I_c(x, y) ∈ [0, 1]) with pixel intensities normalized by minimal and maximal value in local neighborhood (disk-shaped region ${\mathcal{S}}_{xy}$) around each pixel. Resulting contrast-enhanced images show maximally intensified short-scale image gradients and suppressed large-scale image gradients. (B) Schematic of motion tracking procedure with tracking of contrast-enhanced images I_c. The original video images I are deformed using the inverse tracking data $-\overrightarrow{u}$ to obtain motion-stabilized or warped videos I_w(x, y, t), which are then further post-processed, i.e., pixel-wise normalized ($I_w^n$).