simple question about one of "Img()" commands

    for yy=1:Y
        for xx=1:X
            frame = img(max(1,yy-WIN):min(Y,yy+WIN),max(1,xx-WIN):min(X,xx+WIN));

            ma = max(frame(:)); mi = min(frame(:));
            contr(yy,xx) = (ma-mi)/(ma+mi);
        end

what does this phrase mean? "max(1,yy-WIN):min(Y,yy+WIN)"

Answer 1

[Wayne King]

It says create a vector from A to B, where A is the maximum of 1 and yy-WIN and B is the minimum of Y and yy+WIN. That vector is used to index the elements of img(). In other words to select the elements of img() for those row indices. The easiest way to see how this works is to create a simple example for yourself.

   Y = 5; 
   WIN = 2;
   for yy = 1:Y
     max(1,yy-WIN):min(Y,yy+WIN)
  end

[payam]

thanks for your helpful answer. would you also explain what the img( , ) does?

[Wayne King]

img( , ) address the row and column index of img()

img = randn(10,10);
img(1,1) % first row -- first column