Instant 8-bit alpha PNG converter • Hacker News Board

Re: Instant 8-bit alpha PNG converter

#21

Post by pornel » Sun, Apr 17, 2011, 11:27 PM UTC

ck2 wrote: post #19

pornel wrote: post #18

Earlier quoted context omitted.

I was able to convert it without noticeable degradation down to 7 bit: http://geekhood.net/bitcoin-32bit.png http://geekhood.net/bitcoin-7bit.png (using my pngquant)

Yah, after looking at the source I saw they are only using php's gd2 library on 8bitalpha.com which is definitely inferior to your work. The problem is lack of Windows binaries, this is the most modern I can find: http://sites.google.com/site/bitdepthtools/downloads BTW this is the original image I am resampling down to icon size, it seems very challenging because of the multi-layered round edges and many gradients i…

For me OS X screenshots are the toughest — lots of shades in transparent shadow, smooth gray gradients (can't use posterization) AND three small gradients in close/minimize/zoom and couple of odd pixels for anti-alias of corners (can't use pick-most-popular algorithm).

Re: Instant 8-bit alpha PNG converter

#22

Post by pbhjpbhj » Mon, Apr 18, 2011, 11:26 AM UTC

pornel wrote: post #13

I've got improved pngquant that gives significantly better results than original version, gd2 library and often rivals pngnq: https://github.com/pornel/improved-pngquant It is a bit slow (converts image several times feeding back result's quality back to the algorithm), but difference in quality is significant: http://geekhood.net/8bitalpha.png - converted via website http://geekhood.net/imagealpha0.7.png - converted…

Anyone know of a more recent apt repos for pngquant than 1.0-4 (standard Ubuntu repos)?

Re: Instant 8-bit alpha PNG converter

#23

Post by aw3c2 » Mon, Apr 18, 2011, 4:40 PM UTC

pornel wrote: post #13

I've got improved pngquant that gives significantly better results than original version, gd2 library and often rivals pngnq: https://github.com/pornel/improved-pngquant It is a bit slow (converts image several times feeding back result's quality back to the algorithm), but difference in quality is significant: http://geekhood.net/8bitalpha.png - converted via website http://geekhood.net/imagealpha0.7.png - converted…

Any chance to build this with libpng14? I think compiling fails for me because I do have that modern version installed and not libpng12.

Re: Instant 8-bit alpha PNG converter

#24

Post by pornel » Tue, Apr 19, 2011, 8:10 PM UTC

aw3c2 wrote: post #23

pornel wrote: post #13

I've got improved pngquant that gives significantly better results than original version, gd2 library and often rivals pngnq: https://github.com/pornel/improved-pngquant It is a bit slow (converts image several times feeding back result's quality back to the algorithm), but difference in quality is significant: http://geekhood.net/8bitalpha.png - converted via website http://geekhood.net/imagealpha0.7.png - converted…

Any chance to build this with libpng14? I think compiling fails for me because I do have that modern version installed and not libpng12.

It definitely works with 1.4.1, but the bundled Makefile sucks.

Just compile *.c and link it against libpng in whatever way your system requires.

Re: Instant 8-bit alpha PNG converter

#25

Post by pornel » Tue, Apr 19, 2011, 8:12 PM UTC

pbhjpbhj wrote: post #22

pornel wrote: post #13

I've got improved pngquant that gives significantly better results than original version, gd2 library and often rivals pngnq: https://github.com/pornel/improved-pngquant It is a bit slow (converts image several times feeding back result's quality back to the algorithm), but difference in quality is significant: http://geekhood.net/8bitalpha.png - converted via website http://geekhood.net/imagealpha0.7.png - converted…

Anyone know of a more recent apt repos for pngquant than 1.0-4 (standard Ubuntu repos)?

I doubt there will be one, as Greg Roelofs doesn't actively maintain it (I have submitted my changes to him long time ago, and the response was he also got other patches and doesn't have time to merge them).

Re: Instant 8-bit alpha PNG converter

#26

Post by aw3c2 » Thu, Apr 21, 2011, 4:23 PM UTC

pornel wrote: post #24

aw3c2 wrote: post #23

Earlier quoted context omitted.

Any chance to build this with libpng14? I think compiling fails for me because I do have that modern version installed and not libpng12.

It definitely works with 1.4.1, but the bundled Makefile sucks. Just compile *.c and link it against libpng in whatever way your system requires.

Thanks!

I am clueless when it comes to compiling though so for me that stop right at "linking". I only know that that has something to do with those .o files. :-)

I did find http://pngnq.sourceforge.net/ and just installed that.

Re: Instant 8-bit alpha PNG converter

#27

Post by davej » Sat, Apr 23, 2011, 11:50 AM UTC

rimantas wrote: post #20

davej wrote: post #17

Earlier quoted context omitted.

IE7 and IE8 can display 32bit (24bit for RGB + 8bit for alpha channel) PNGs fine by the way. IE6, of course, only supports alpha transparency on 8bit PNGs.

IE6, of course, only supports alpha transparency on 8bit PNGs. IE6 does not support alpha transparency, in this case it treats colos with alpha component as fully transparent i.e. PNG8 with alpha transparency is treated as with index transparency.

Yes, you're correct.