clear all

A = [0 128; 192 255]
a = A(2,1)
b = A(1,2)
image( A )
colormap( gray ( 256 ) )
axis image

B = [1 2; 3 4]
image(B)
colormap( gray ( 256 ) )
axis image
imagesc(B)
colormap( gray ( 256 ) )
axis image
whos % double is default