This quantitative image analysis tool is used to characterize key structural properties of nanoparticle clusters from experimental images of nanocomposites. This analysis can be carried out on images captured at intermittent times during assembly to monitor the time evolution of nanoparticle clusters in a highly automated manner. The software outputs averages and distributions in the size, radius of gyration, fractal dimension, backbone length, end-to-end distance, anisotropic ratio, and aspect ratio of nanoparticle clusters as a function of time along with bootstrapped error bounds for all calculated properties. The polydispersity in nanoparticles and biases in the sampling of nanoparticles clusters are accounted for through the use of probabilistic weights.