min_ max_ Gray operator understanding

# How to understand min_max_gray operator

min_max_gray(Regions,Image::percent:Min,Max,Range)
This operator is used to extract Regions The maximum and minimum gray values of the image in the region ,
The key is ***percent*** The understanding of this parameter .
First, calculate the gray histogram of the image in the region , That is to say 0-255 Distribution frequency diagram of the number of image pixels within the gray value range . Area times ***percent*** Get a number , Set to a, And then use ***a*** Respectively from the 0 Gray value and 255 Intercept inward at the gray value ***a*** Pixels . Then take the minimum and maximum gray value in the remaining pixels .
e.g.:

histo:=[4,1,1,1,…1,5,3,1], The middle is full of 1, |histo|:=256 ,histo Deposit 0-255 The number of pixels of each gray value in the gray range , if a:=4 be min:=1,max:=253,range:=252

***percent*** The main function of is to reduce the amount of calculation , Remove the influence of minimax to try to get the minimum and maximum value of your desired gray value . To get better image gray features .