Downscaling-based segmentation for unresolved images of highly heterogeneous granular porous samples

We propose a simple and efficient algorithm of downscaling followed by segmentation to reconstruct the unresolved pore space from X-ray computed tomography (XCT) images of natural geological porous media
columns. Contrary to widely employed single and multilevel threshold-based segmentation, the proposed method is based on a continuous map between pixel intensity and local pixel porosity that does not rely on the definition of arbitrary thresholds. The approach is used to generate a high-resolution binary image of the porous medium from poorly resolved grey-scale images while preserving available sub-resolution information.