bug#74476: [PATCH] Explore JPEG loading without quantization

[Manuel Giraud via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>]

Alan Third <alan@idiocy.org> writes:

> On Sat, Nov 30, 2024 at 06:25:01PM +0100, Manuel Giraud wrote:
>> Here is a new version with Alan suggestions.
>> 
>> FTR, the gain is much less interesting.  Here is the new timing with
>> same benchmark (see below):
>> (4.381739669 1 0.1034133749999997)
>
> That's unfortunate, although here I see an improvement of greater than
> 2x.

That's good news.

> Probably I could do with finding some larger images as the whole thing
> completes in under a second even without your patch.

FYI, I have used images of 4000 by 3000 pixels.

> I've had a quick dig into lookup_rgb_color and assuming you have a
> true colour display and there's no gamma calculation going on (I don't
> know when that happens) it shouldn't be doing a whole lot more.
> Perhaps it's just the extra over-head of calling a function?

It seems a bit much for just a function call.  Or maybe it is the
init_color_table call?  Should it be done for each jpeg_load?
-- 
Manuel Giraud