*2.6. IR Image Preprocessing*

All images were preprocessed with the extended multiplicative scatter correction (EMSC) algorithm which included correction of the baseline, variations related to the difference in sample thickness, and vector normalization. Indeed, this step allowed removing the outliers and artifacts that can influence spectral image analysis. All spectral images were preprocessed in the 1800 to 900 cm−<sup>1</sup> spectral region using a developed in-house routine in Matlab (The Mathworks, Natick, MA, USA).
