[XviD-devel] lossless rescale

[Florin Andrei]

Recently, i've seen on Freshmeat an announcement of a software that
claims to perform "lossless JPEG rescale".
According to the author, the logic is like this: normally, an
application like Gimp, when rescaling a JPEG image, it actually performs
a conversion to plain bitmap, applies the rescale algo to the bitmap,
then converts the bitmap back to JPEG. Because JPEG is a lossy format,
the whole process brings a noticeable loss of quality.
Now, if the program knows "everything" about JPEG, a transformation
could be applied without going through decoding to bitmap / recoding to
JPEG. Therefore, the loss of quality is much smaller, if any.

I wonder if a similar thing can be done to DivX. Is it possible, at
least theoretically?
If it is, does the codec needs to provide some special hooks in the API?

-- 
Florin Andrei

http://florin.myip.org/