Instant 8-bit alpha PNG converter

pedrokost wrote: post #2

Thank you a lot for the tool. I had no idea I could compress PNG so much, without loosing too much quality. I will be a heavy user of this.

To clarify, I didn't make this site, just discovered it while googling how to accomplish this without Fireworks.

The "beauty" of 8-bit png is how it degrades acceptably in IE8, IE7 and even IE6.

Try comparing a large round icon in 1-bit alpha (ie. gif) vs 8-bit alpha, it's much much better.

Re: Instant 8-bit alpha PNG converter

#5

Post by aw3c2 » Sun, Apr 17, 2011, 3:14 PM UTC

What is the difference to using say optipng?

Re: Instant 8-bit alpha PNG converter

#6

Post by nathos » Sun, Apr 17, 2011, 3:21 PM UTC

Mac users should check out ImageAlpha for optimizing 8-bit PNGs: http://pornel.net/imagealpha

Re: Instant 8-bit alpha PNG converter

#7

Post by ck2 » Sun, Apr 17, 2011, 3:22 PM UTC

aw3c2 wrote: post #5

What is the difference to using say optipng?

optipng/pngout/pnggauntlet are "only" png optimizers

this site gracefully degrades a png with 24bit alpha transparency to 8bit alpha so you don't have to settle for a gif.

I suspect they are using pngnq http://pornel.net/pngnq and pngquant http://pornel.net/pngquant

Some background here:

http://blogs.sitepoint.com/png8-the-clear-winner/

http://www.ethanandjamie.com/blog/81-png8-transparency-witho...

That site is great because it's so easy, they did some very impressive drag-and-drop code and it makes very high quality output that is as good as Fireworks.

Re: Instant 8-bit alpha PNG converter

#8

Post by TillE » Sun, Apr 17, 2011, 3:29 PM UTC

ck2 wrote: post #7

aw3c2 wrote: post #5

What is the difference to using say optipng?

optipng/pngout/pnggauntlet are "only" png optimizers this site gracefully degrades a png with 24bit alpha transparency to 8bit alpha so you don't have to settle for a gif. I suspect they are using pngnq http://pornel.net/pngnq and pngquant http://pornel.net/pngquant Some background here: http://blogs.sitepoint.com/png8-the-clear-winner/ http://www.ethanandjamie.com/blog/81-png8-transparency-witho... That site is grea…

Yeah, most of the compression seems to come from converting from RGB to colormap with pngquant.

I wonder if it's possible to do all this with an ImageMagick one-liner.

Re: Instant 8-bit alpha PNG converter

#9

Post by ck2 » Sun, Apr 17, 2011, 3:30 PM UTC

nathos wrote: post #6

Mac users should check out ImageAlpha for optimizing 8-bit PNGs: http://pornel.net/imagealpha

I was actually looking for a Windows equivalent to that when I found this wesite.

Re: Instant 8-bit alpha PNG converter

#10

Post by beej71 » Sun, Apr 17, 2011, 3:35 PM UTC

aw3c2 wrote: post #5

What is the difference to using say optipng?

Here's a real example, using a test image that has a lot of different alpha values in it, and a 24-bit alpha channel:

    Original:    87047 bytes
    optipng -o7: 82489 bytes
    this tool:   22585 bytes

The main difference, other than size, is that optipng produced an exact copy of the the original, while this tool is lossy, and threw away a bunch of data from the alpha channel. The win is that for the majority of all web cases, 8 bits of alpha is plenty.