Re: Shrinking a picture --- and it becomes blur !!

bugbear <bugbear@[EMAIL PROTECTED]
> writes:

>> Or try the "Lanczos" algorithm

>Since the downsize is an exact integer (factor of 8)
>I'm not sure Lanczos (or anything "better" than bilinear)
>would help.

The fact that the downsize ratio is an integer factor means it's easy to
use a box filter
for the downsizing and get "not bad" results.  That doesn't mean Lanczos
would not be better
yet.  A box filter still produces a fair amount of aliasing due to letting
through input
image frequency components that are above the Nyquist limit for the output
resolution.
Lanczos is better at attenuating these frequencies and suffers less
aliasing artifacts.  At
the same time, it's better at retaining frequencies just below Nyquist
that a box filter
attenuates more than necessary.

Now, a reasonable-sized Lanczos downsampling filter will cost you more
time than a box
filter - but it should be small compared to the original render time.

	Dave