Fig. 4
From: Contamination-free non-contact wettability assessment system
Image processing instrumentation for detecting liquid-squeezed area and estimating the diameter of a circular shape. a Flowchart of image processing for liquid-squeezed area detection and diameter estimation. Photographs b–d show part of the experimental setup, liquid behavior as monitored by the digital camera, and the result of the liquid-squeezed area detection, respectively (see also Additional file 3: Movie 1). Photographs e–g show the detected results of printed circular patterns with diameters of 5, 10, and 20 mm, respectively, for confirming the estimation accuracy. Black scale bars in photographs c–g indicate 1 cm. Graph h shows the relationship between measured and actual sizes of circular patterns. The dotted line in graph h indicates the linear approximation line for data points obtained using the linear regression equation and the coefficient of determination R 2 is 0.999