Image Processing and Analysis for Fractal Dimension and Lacunarity Calculation of Waxy Oil Gels Using Polarized Light Micrographs

Wax crystals emerge and grow during the cooling of waxy oils and may be monitored by polarized light microscopy. However, the micrographs obtained have a significant amount of diffuse light, which distorts the crystals and may hinder the measurements of the length and structural properties. One solution for this is to perform an image processing and analysis protocol capable of dealing with uneven light. This work aims to study micrographs of a model waxy oil under polarized light in a concentration range of 2.5 to 7.5 wt % under cooling rates of 0.5 to 1.0 °C/min and investigate the calculation of their fractal dimension, lacunarity, area fraction, crystals number, and length by applying top-hat morphological filters for image quality enhancement. Therefore, by establishing a protocol based on a white top-hat filter, it is shown that it is possible to monitor the crystal dynamics, especially concerning structural fractal dimension and lacunarity. An increase in the wax crystals’ fractal dimension is observed under cooling, which means that the crystals’ network gets more intricate as the lacunarity decreases and the sample becomes more compact. As an outcome, a new benchmark for image processing and analysis of polarized light micrographs of waxy oil is obtained.