A computationally efficient solution to the problem of minimum error thresholding has been derived under the assumption of object and pixel gray level values being normally distributed. The principal idea behind the method is to optimise the average pixel classification or an iterative algorithm. The method is applicable in multithreshold selection.
2019-4-3 A Threshold Selection Method from Gray-Level Histograms - Otsu二值化算法
The number of pixels at level i is denoted by①ni and the total number of pixels by N.
①denote:
- 1] to be a sign of sth. 标志，预示，象征。
- 2] to mean sth.(=represent，~connote 暗示，隐含) 表示，意指。
The proposed method is characterized by ① its nonparametric and unsupervised nature of threshold selection and has the following desire advantages.
A. The procedure is very simple; only the zeroth and the first order cumulative moments of the gray-level histogram are utilized.
B. A straightforward extension to multithresholding problems is feasible ② by virtue of ③ the criterion on which the method is based.
C. An optimal threshold(or set of threshold) is selected automatically and stably, not based on the differentiation(异化) (i.e., a local property such as valley), but on the integration (i.e., a global property) of the histogram.
D. Further important aspects can also be analyzed (e.g., estimation of class mean levels, evaluation of class separability, etc).
E. The method is quite general: it covers a wide scope of unsupervised decision procedure.
①is characterized by: 以…为特征。
②feasible: that is possible and likely to be achieved. 可行的，行得通的。 economically / technically / politically etc feasible.
③by/in virtue of: by means of or because of. 凭借，依靠；由于，因为
2019-3-31 Frequency-tuned Salient Region Detection - FT算法
The norm of the difference is used since we are interested only in the magnitude of ① the differences.
①magnitude：
- 1] [U] the great size or importance of sth; 巨大。the degree to which sth is large or important；重大，重要性；
- 2] [C,U] the degree to which a star is bright；星体的亮度
- 3] [C,U] the size of an earthquake；震级