[Ohrrpgce] SVN: teeemcee/11357 Allow jpg/jpeg as a screenshot format (gfx.screenshot_format setting)

[Ralph Versteegen]

No fair, how come you recieved this svn commit email at least an hour ago,
but I got it just now? It's pretty annoying that the emails are so delayed.

Anyway, the reason that I added a jpeg encoder is that I've been
investigating how to store graphics in compressed format inside .rgfx lumps
(err... post Fufluns). Embedding .png and .jpg files inside .rgfx is
certainly not to my liking. I've been doing a LOT of experiments with 24bit
backdrops and reached the unavoidable conclusion that JPEG at quality 90-95
blows everything else out of the water for lossy compression of backdrops,
unless you want to want to use something better like FLIF or BPG or
HEIC/HEIF or WEBP which would require a huge (and slow!) library to
decode/encode. And JPEG file format is actually pretty simple, unlike e.g.
PNG. So there's no reasonable alternative to embedding JPEGs inside .rgfx
for that use case.
However, JPEG doesn't support an alpha channel, so that's one problem
(it'll need to be stored separately). And it's not suitable for tilesets or
sprites (it's uncompetitive for compression of repetitive images anyway).

On the other hand it looks like there's no reason to embed PNG; it's not
hard to beat it with something much simpler because it's a complex file
format around a pretty simplistic compression method.

On Tue, 29 Oct 2019 at 22:44, James Paige <Bob at hamsterrepublic.com> wrote:

> Neat! :)
>
> On Tue, Oct 29, 2019, 5:24 AM <subversion at hamsterrepublic.com> wrote:
>
>> teeemcee
>> 2019-10-29 02:24:41 -0700 (Tue, 29 Oct 2019)
>> 69
>> Allow jpg/jpeg as a screenshot format (gfx.screenshot_format setting)
>> ---
>> U   wip/allmodex.bas
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