Re: [Gimp-user] Sinc (Lanczos3) Option]

[Ken Moffat <zarniwhoop ntlworld com>]

Whoops, managed to reply to sender instead of replying to the list.

----- Forwarded message from Ken Moffat <zarniwhoop ntlworld com> -----

Date: Sun, 5 Aug 2018 20:20:51 +0100
From: Ken Moffat <zarniwhoop ntlworld com>
To: "Lisa D." <stellabella242 gmail com>
Subject: Re: [Gimp-user] Sinc (Lanczos3) Option
User-Agent: Mutt/1.10.1 (2018-07-13)
Message-ID: <20180805192051.GA18646@milliways.localdomain>

On Sun, Aug 05, 2018 at 11:13:01AM -0700, Lisa D. via gimp-user-list wrote:
> Hi! I would like to stretch/resize an image without distorting it. I
> downloaded GIMP 2.10.4 but was not able to do this with this version of
> GIMP. After a few google searches, I found an article stating that you need
> GIMP 2.4 to do this because you need to use the “Sinc (Lanczos3)” option
> under Quality>Interpolation in the Scale Image dialog. I checked the
> version I have and, lo and behold, 2.10.4 does not seem to have this
> option.
>
> So, I would love to get my hands on GIMP 2.4, but it seems to only be
> available now via third party sites that seem wholly unaffiliated with gimp
> and, to be honest, look a little hinky to me. Does anyone know of a site
> like this that is, in fact, safe and trustworthy? Or another way to get
> 2.4? It doesn't seem to be available on gimp.org. Please let me know if you
> have a moment and I'll try to pass it forward when get more gimp skills
> under my belt. I have Windows 10, in case it helps to know that.
>
> Thanks in advance!

I suspect you have been misled by an old article : 2.4 is now
perhaps best described as 'antique'.  I think that this option was
in 2.8, but was dropped in 2.10 : since nobody likes losing quality,
I guess that the developers think the available options are good
enough.  A lot of the internal details changed in 2.10 (more use of
gegl).

But your terminology disturbs me - if you scale up an image, it
should not be distorted (image | scale image) unless the original
image is a jpeg and artifacts appear.  But stretching an image
implies distorting it to make things relatively wider (or higher).

Maybe I've misunderstood, but I suggest you take an example image in
2.10.4, scale it to your desired size with the various available
options : do this several times, starting from the original each
time, use a different option and save to a separate xcf file (so -A,
-B or whatever : I don't have gimp on the machine I'm replying
from), then export a png from each and compare them.

If there is indeed a problem, then consider trying the latest 2.8
version *probably 2.8.22) where that option should be available -
use that, again create a png, compare to the results from 2.10.4.
If that turns out to be equally bad, it's probably either artifacts
in the original, or excessive scaling.  But if 2.8 is better then
please raise a bug.

Many things changed in 2.9 and a few have changed in 2.10.
Sometimes we need to modify our process to get the results we want.

ĸen
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