“…Greening, as an external defect, was successfully detected based on tuber surface color by Tao et al (1995a), Zhou et al (1998), Noordam et al (2000, and Dacal-Nieto et al (2009), with classification rates of defected tubers of 90%, 78.0%, 88.1%, and 86.2%, respectively. Sorting and grading tubers could be a difficult mission with the singulation problem as a result of the possible interference between different touching objects (Marchant et al, 1990;Al-Mallahi et al, 2010a). It was possible, however, to build grading systems for tubers based on size by developing several separating techniques, applied on the captured images, such as the blob splitting algorithm (Marchant et al, 1990), the 8-neighbor labeling algorithm (Al-Mallahi et al, 2010a), or based on intensity threshold (Dacal-Nieto et al, 2009).…”