Re: [gentoo-user] Your opinion on jpeg encoders, please

[Mark Knecht <markknecht@gmail.com>]

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On Mon, Jan 4, 2021 at 2:38 PM Frank Steinmetzger <Warp_7@gmx.de> wrote:
>
> Hi all,
>
> this is not really a Gentoo-specific question, but some of you know your
way
> around stuff, so here goes.
>
> When I edit photos, I like to shrink and recompress them to save on space,
> but not mangle them too much in the process to lose quality. So for
average
> images I tend to use a quality setting between 80 and 86, very bad shots
> such as defocussed or blurred ones just 70. And for the really good ones
> (crystal sharp, portraits, extraordinary motives etc) 90 and more.
>
> In the far past I’ve been using Gimp, but for some years now mostly
Showfoto
> (the editor from Digikam) due to its more useful photo enhancement
features.
>
> However I noticed that the latter procuces larger files for the same
quality
> setting. So currently, I first save with a very high setting from Showfoto
> and then recompress the whole directory in a one-line-loop using
> imagemagick’s convert. I have the impression that it produces far smaller
> files at the same visual quality.
>
>
> Now I know that one can’t fully compare quality settings of different
> encoders, but it started me wondering: which is really “better”? Or maybe
> just a little more enhanced, or up-to-date from an algorithmic standpoint?
>
> Just because many distros and tools use libjpeg, that doesn’t mean it’s
the
> best one out there. Gimp, showfoto and convert use different encoders,
> because compressing the same PNG with the same JPEG setting does not
result
> in three identical files.
>
> Does any of you have an opinion on that matter?
> Cheers.
>
> --
> Gruß | Greetings | Qapla’
> Please do not share anything from, with or about me on any social network.
>
> What do you call a man with a seagull on his head? – Cliff.

This topic comes up a lot with astrophotography. I took about 150 24M pixel
shots last night. It uses a lot of disk space.

From my reading - which isn't a lot - it seems to be technically superior
to simply downsample the original and then compress with jpeg if you need
to go that far vs using higher jpeg compression ratios on the original.

I have no data to back this up and it probably depends a lot on your source
material so YMMV but it's an option.

HTH,
Mark

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