Bilinear filtering is one
method in
computer graphics for making
pixels look
smoother when
drawing to the
screen. (Another is
bicubic filtering, which looks much nicer, and will be discussed later).
So to kick this off, a bilinear
graph looks like this:
/|\
/ | \
/ | \
/ | \
/ | \
/ | \
/ | \
-------------
Now take the
origin as the
pixel whose color is to be
calculated. The theory goes is that each pixel directly next to that one factors in
heavily, and, up to a certain threshold, each pixel after that factors in
inversly proportional to its
distance from the pixel in question. Obviously the pixels original color factors in the greatest when determining the final
color. Most filtering
algorithms have to make a
second pass at the entire pixel table to do this sort of filtering, although some really great implementations use some a lot of numbers and some scary
math to accomplish it in one pass.
Bilinear filtering is an
additive filter applied to the pixel grid, while Bicubic is subtractive. The only problem is that this method of graphical filtering tends to look a little fuzzy when all is said and done. Because of this woe, the slightly more complicated bicubic filtering was developed, whereby pixels at the end sharpen picture by
subtracting from the final color.