Figure 4
From: SHERPA: an image segmentation and outline feature extraction tool for diatoms and other objects
Multiple shapes (highlighted red) detected for a diatom valve according to different segmentation procedures (compare to Figure3). a) Otsu’s thresholding, b) Otsu’s thresholding combined with histogram equalization, c) robust automated threshold selector (RATS), d) adaptive thresholding, e) Canny edge detector. Only the result matching best to one of the templates (according to elliptic Fourier analysis, see below under "Shape identification") is taken for analysis.