Image Processing Reference
In-Depth Information
FIGURE 1 Sample images for all thresholding techniques: (a-c) original images,(d-c) Otsu
results, (g-i) g90 results, and (j-l) g100 results. Note that (e), (g), and (l) are outputs of the best
thresholding method for each case.
2.1.1 Otsu threshold
For Otsu's thresholding [ 8 ] , firstly a gray level image is generated from an input color image.
Then, for each possible intensity threshold, the variance of spread of pixels in the foreground
and background region is calculated. The intensity ( τ 0 ) for which the sum of foreground and
background spreads is minimal is selected as the threshold. Pixels with gray level intensity
higher than ( τ 0 ) form the foreground region while the remaining pixels form the background.
Figure 1 (d-f) shows some sample binary images of Otsu's method.
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