RAFT: A program for area fraction measurement of digital micrographs

Measuring the volume fraction of a constituent is a frequent requirement for materials characterization. One method for doing so is measuring the area fraction of the constituent captured in digital micrographs as an approximation of the volume fraction. Area fraction measurements are often automated using computer algorithms. These algorithms can be sensitive to imaging conditions, such as the feature-background contrast, which can introduce significant uncertainty into reported values. In this work, we developed a point-counting algorithm that can measure area fraction to a user-specified degree of precision, ensuring an efficient sample size selection based on the needs of the characterization effort. The algorithm is then implemented into an open-source software, Robust Area Fraction Tool (RAFT), that facilitates sample size calculation and point-counting. Performance of the algorithm was quantified on both simulated and real digital micrographs, and the results showed the algorithm met or exceeded desired precision values in almost all test cases.