[Scummvm-devel] Moving and merging image-related code

[Willem Jan Palenstijn]

On Wed, Feb 02, 2011 at 09:13:01PM +0200, Filippos Karapetis wrote:
> The discussion boils to "do we want to have our own code for handling file
> formats, or use external libraries?"

I don't think that's what the discussion boils down to at all, and see no
reason why we should treat everything the same. I think we should ask this
question on a case-by-case basis, based on things like code size,
maintainability, portability, performance.

At this point there seems to be no concrete gain to dumping libpng, since the
platforms where we use it for sword25 seem to have no issues with libpng?

Unless it's an issue on the PSP where we also seem to use libpng?


-Willem Jan


 
> On Wed, Feb 2, 2011 at 8:54 PM, Johannes Schickel <lordhoto at scummvm.org>wrote:
> 
> >  On 02/02/2011 07:04 PM, Filippos Karapetis wrote:
> >
> >
> >  > png.*
> >> As I expressed on IRC, I disagreed with having our own PNG decoder and
> >> I would much rather see libpng used. The dependency on libpng is not
> >> something that would be ridiculous to depend on and we will most
> >> likely never equal the speed of libpng.
> >
> >
> >  Why? We don't need all of the functionality of libpng, and it's not like
> > we absolutely
> > need top speed when loading an image. We have our own code for all the
> > other
> > image formats, why is it so wrong in having our own code for PNG as well?
> > One
> > less dependency is a good thing in my eyes, especially if it allows us to
> > port the
> > game in other platforms and not worry about libpng availability there. So,
> > I personally
> > don't understand why libpng is better for our needs.
> >
> >
> >
> > Uhm, don't we already use libpng for PNG loading in Sword2.5 and the PSP
> > backend? I rather thought this was about moving the decoders to its own
> > subdirectories (+ unifying the API) instead of duplicating the code and not
> > about how to implement the loader?
> >
> > Ahh I see Md5 implemented a custom PNG loader... well I am not too happy
> > about that. I do not think libpng is a library which is hard to port (you
> > can proof me wrong here though), also why should we spend time writing a
> > good (i.e. consider speed, memory consumption, fail safenes, etc.) PNG
> > loader/(encoder?) implementation, when we can just use libpng? That seems
> > wasted time we could rather put into improving our other code IMHO.
> > Personally I am not sure why we do not use libjpeg for JPG loading...
> >
> > Also we should consider the target systems of the engines we use those
> > image loaders for, just take Sword2.5, on which devices are we likely to get
> > it to run and which device of these will have any problem with a libpng
> > depandancy?
> >
> > All this seems premature optimization to me, if we have a stable image
> > decoding API we can exchange the implementation when we have any problems
> > later on anyway, so why do we now want to implement every standard image
> > format loader out there ourselves? Just to not depend on a library which is
> > (probably) pretty easy to use on most of our target systems? That reasoning
> > seems strange to me....
> >
> > Since you mention loading speed: Didn't we have some problems with the JPG
> > loader being slow and thus we needed to optimize it (or still do? I remember
> > something about that and if anyone would remember the details I would be
> > most pleased if he / she could clarify that here.
> >
> > // Johannes
> >
> >
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> 
> -- 
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