PNG viewer plugin

[zajacattack]

So, I was looking into adding a PNG viewer into rockbox. Would libpng work for this? (See http://www.libpng.org/pub/png/libpng.html)

[Llorean]

As long as it's GPL licensed, and can be made to require little enough RAM *anything* will work, the question always boils down to "how much work will it take to convert it, and how fast will it be afterward."

[GodEater]

I looked into this a while ago, and at least to me, it looked like quite a lot of work. Most of libpng is done using floating point arithmetic, and that alone would mean quite a lot of work getting it ported to Rockbox. I kind of stopped my analysis at that point, since I've never looked into what's required for floating point to integer arithmetic conversion, and at the time, didn't really have the motivation to get my reading books out

[crash91]

I think it would be really great if this was implemented. It would be even better if it was integrated into the RB core, because WPS designers would then be able to use the Aplha channel for transparency in PNGs  
But anyway, as GodEater said, its a lot of work, but it would be nice if implemented.

[LambdaCalculus]

Llorean: libpng's license page:

http://www.libpng.org/pub/png/src/libpng-LICENSE.txt

No idea what kind of license that is. It's just listed as "Open Source" on the front page.

[cool_walking_]

Wiki knows ALL.

Released under the permissive free software licence used by zlib,[1] libpng is free software.

It is compatible with the GNU General Public License.

[LambdaCalculus]

Ahh, good to know.  

[zajacattack]

I looked into this a while ago, and at least to me, it looked like quite a lot of work. Most of libpng is done using floating point arithmetic, and that alone would mean quite a lot of work getting it ported to Rockbox. I kind of stopped my analysis at that point, since I've never looked into what's required for floating point to integer arithmetic conversion, and at the time, didn't really have the motivation to get my reading books out

So, what is the problem with floating point arithmetic, and why is it necessary to convert it to integer arithmetic?

[safetydan]

None of our targets (bar possibly the Gigabeat S IIRC) have a floating point unit (FPU). Without an FPU, floating point maths has to be emulated (including all the malarky required for IEEE 754) by the CPU which is incredibly slow.

Hence the need to convert floating point to fixed point (i.e. integer) maths.

Edit: minor typo corrections.

[pabouk]

Libpng should already have fixed point implementation included See http://groups.google.com/group/mozilla.dev.platforms.mobile/browse_thread/thread/504332475973e42d.