Picturing an Image as a 2D Function
An ideal image can be viewed as a function, I(x, y), that gives an intensity
for any given coordinate (x, y). We could plot this function as a height field.
This plot would lowest at dark points in the image and highest at bright points.
Most of the functions that we encounter are analytic and, therefore,
can be expressed as simple algebraic relations. An image, in general, cannot
representaed in such a simple form. Instead, we represent images as tabulated
So how do we fill this table?