Re: RAW images...

Kennedy McEwen <rkm@xxxxxxxxxxxxxxxxxx> wrote:
In article <871ww8641g.fld@xxxxxxxxxx>, Floyd L. Davidson
<floyd@xxxxxxxxxx> writes
Kennedy McEwen <rkm@xxxxxxxxxxxxxxxxxx> wrote:
Well, I have checked it time and time again with different
images since you raised it and so far I haven't observed it once
at a compression rate that gives a file size about the same as
the original. It does become a problem if you increase the
compression rate to get a file size of half or less of the
original, but I suspect you would get similar problems without
any resizing anyway. So, in practice, it is a non issue.

Your inability to observe the effects does not make it a
non-issue for critical work.

Your claim wasn't that this was only relevant to critical work,
but that the effect was *significant* (serious and noticeable) -
it isn't. If the elimination of minute deviations from the
original scene was critical then we wouldn't be discussing JPG
in any case, as already established in the thread. That doesn't
mean that JPG cannot be used for useful, even great, images -
even after resampling *and* recompression.

If you cannot honestly discuss what I have said, without this
sort of exaggeration and distortion, what sense is there in
having a conversation?

In fact *any* change that causes the boundary for quantization
to change in non-multiples of the original will have the same
effect.

In other words, it is NOT an issue that is restricted to JPEG
images! Any resizing changes the quantisation - that is what
resampling is!

Who said JPEG is the only lossy format?

If, for example, that is originally done on 8 pixel
boundaries, then shaving 2 pixels off the edge of the image
and saving it will have the indicated effects...

First off, 2 pixels in 8 is 75% resampling, not 95%, but that is
by the way.

Nobody has mentioned 95% resampling at any point in this
exchange.

What you are demonstrating is a complete failure to
understand the concept of the JPEG algorithm.

I've demonstrated that *you* lack that understanding. And again
we see that you cannot respond without distorting what others
say. That demonstrates an inherent lack of integrity. And I am
not willing to tolerate more of it.

Plonk.

--
Floyd L. Davidson <http://www.apaflo.com/floyd_davidson>
Ukpeagvik (Barrow, Alaska) floyd@xxxxxxxxxx
.

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