how to use square filter with value 4 for erode function

f=imread('gee.jpg');
se=strel('train',4);
k=imerode(f,se);
imshow(k);

Answer 1

[Image Analyst]

'train' is not one of the options. Not sure what you want, but maybe you want to consider the 4 closest neighbors

grayImage = imread('gee.jpg');
se = [0,1,0; 1,0,1; 0,1,0];
erodedImage = imerode(grayImage , se);
imshow(erodedImage);