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On Mon, Jan 4, 2021 at 2:38 PM Frank Steinmetzger <Warp_7@×××.de> wrote: |
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> |
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> Hi all, |
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> |
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> this is not really a Gentoo-specific question, but some of you know your |
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way |
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> around stuff, so here goes. |
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> |
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> When I edit photos, I like to shrink and recompress them to save on space, |
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> but not mangle them too much in the process to lose quality. So for |
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average |
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> images I tend to use a quality setting between 80 and 86, very bad shots |
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> such as defocussed or blurred ones just 70. And for the really good ones |
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> (crystal sharp, portraits, extraordinary motives etc) 90 and more. |
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> |
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> In the far past I’ve been using Gimp, but for some years now mostly |
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Showfoto |
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> (the editor from Digikam) due to its more useful photo enhancement |
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features. |
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> |
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> However I noticed that the latter procuces larger files for the same |
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quality |
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> setting. So currently, I first save with a very high setting from Showfoto |
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> and then recompress the whole directory in a one-line-loop using |
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> imagemagick’s convert. I have the impression that it produces far smaller |
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> files at the same visual quality. |
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> |
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> |
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> Now I know that one can’t fully compare quality settings of different |
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> encoders, but it started me wondering: which is really “better”? Or maybe |
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> just a little more enhanced, or up-to-date from an algorithmic standpoint? |
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> |
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> Just because many distros and tools use libjpeg, that doesn’t mean it’s |
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the |
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> best one out there. Gimp, showfoto and convert use different encoders, |
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> because compressing the same PNG with the same JPEG setting does not |
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result |
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> in three identical files. |
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> |
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> Does any of you have an opinion on that matter? |
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> Cheers. |
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> |
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> -- |
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> Gruß | Greetings | Qapla’ |
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> Please do not share anything from, with or about me on any social network. |
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> |
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> What do you call a man with a seagull on his head? – Cliff. |
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This topic comes up a lot with astrophotography. I took about 150 24M pixel |
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shots last night. It uses a lot of disk space. |
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|
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From my reading - which isn't a lot - it seems to be technically superior |
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to simply downsample the original and then compress with jpeg if you need |
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to go that far vs using higher jpeg compression ratios on the original. |
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I have no data to back this up and it probably depends a lot on your source |
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material so YMMV but it's an option. |
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HTH, |
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Mark |
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