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

["Walter Dnes" <waltdnes@waltdnes.org>]

On Mon, Jan 04, 2021 at 10:37:34PM +0100, Frank Steinmetzger wrote
> 
> 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.

  Actually, shrinking *BY AN INTEGER NUMBER SHOULD IMPROVE QUALITY* as
well as saving space.  In Google look up the phrase...

photography binning adjacent pixel

  If you bin a 3840x2160 image by 2, you'll get a 1920x1080 result.  If
you bin it by 3, you'll get 1280x720 image.  The math is a bit
convoluted, but when you bin by a value of "n"...

* the information per combined pixel increases by a factor of "n"

* the noise per combined pixel increases by a factor of square root of "n"

  So the "signal-to-noise-ratio" increases.  The resulting image is less
noisey.  The tradeoff is that the new image is smaller than the original.
I use the imagemagick "convert" utility from the commandline, but any
capable image software should work.

-- 
Walter Dnes <waltdnes@waltdnes.org>
I don't run "desktop environments"; I run useful applications