I am taking a computer vision class and I have just learnt about the Harris corner detection concept. A corner is detected when a small shift in a window function defined around the corner results in a large $E(u,v)$ term, which is the sum of squared difference of pixels between the previous window and the next window. There is a post on this forum that has a very nice conceptual explanation about harris corner detectors.
However, given that $E(u,v)$ should be large for small changes in $(u,v)$, why is $E(u,v)$ function usually depicted as a function that has a negative maxima ? Shouldn't $E(u,v)$ value be high when $(u,v)$ is close to $(0,0)$