Photoshop: Support PNG8 with alpha transparency, just like Fireworks

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Fireworks has a useful feature to produce PNG8 with alpha transparency. Photoshop could really use this capability.

Further reading:
http://www.ethangardner.com/articles/...
http://blogs.adobe.com/jnack/2010/08/...
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Marian Driscoll

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Posted 6 years ago

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Chris Cox

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Photoshop CS6 can read those files, but cannot write them yet.
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Jonas M. Rogne

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Now for the 2nd half... ;)
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Peter Schwarz

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the PNG v1.0 spec from 1996 already features the tRNS chunk that allows real transparency for the indexed palette of any given PNG8. Browsers have been supporting PNG8+Alpha for ages. It's nothing short of embarassing that Adobe STILL ignores this extremely useful feature, since especially in the modern HTML5 web real transparency is *absolutely* necessary!...

Ever since I discovered it I haven't been using anything else. And now I always have to store the PNG32 versions, too, just because Photoshop cannot open PNG8+Alpha properly! And no, PNGout is *not* a solution!...

Oh, and while we're at it: Could you *please* bring the ancient "Save for web" color quantizer into the 21st century? Comparing its results to the results of e.g. PNGquant or tinypng.org is nothing short of embarassing!...
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Matt

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PNG8 alpha transparency has been a lifesaver in reducing image asset sizes for the web. Please allow us to keep our workflow in Photoshop by supporting what you already gave us in Fireworks.
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Nijntje

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PNG8 is one of the few things that might bring HTML5 closer to the amazing image compression of Flash image data (where alpha transparency is saved like 8-bit png and color like JPG or PNG).
Even better would be something that lets you control features like:
- posterization of alpha (For antialiasing only, 16 shades of alpha are often sufficient)
- control quantization weight (alpha color)
- control dither for color and alpha separately
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Jonas M. Rogne

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PNG-8 with real/alpha transparency would be very useful for web.

Often graphics need proper transparency, and PNG-24 creates files that are too large. It's embarrasing and inconvenient having to use a couple of open-source programs to recompress the PNG-files after "saving for web" from Photoshop.

Nijntje's suggestions are great as well.
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Jonas M. Rogne

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This has finally been added by the way, in the Export As... dialog.
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JEA

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I'm not sure.

How do you interpret this from here:

https://helpx.adobe.com/photoshop/using/whats-new-cc-2015.html

  • PNG format changes for asset export. The Format pop up menu now includes a simplified PNG option.
    • Selecting Transparency with PNG generates 32-bit PNG assets.
    • Selecting Smaller File generates 8-bit PNG assets.
    • Leaving the above options deselected generates 24-bit PNG assets


The above is referring to the File>Export As  in photoshop.
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Jonas M. Rogne

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  • A 32-bit PNG here would be 8 bits per color channel ("PNG-24") and 8-bit for the transparency. Like in the old Save for web.
  • An 8-bit PNG here would be 8 bits total for the color ("PNG-8"). So 256 colors. One of the colors can not be defined as transparent like in the Save for Web dialog.
  •  A 24-bit PNG here would be 8 bits per color channel ("PNG-24") and no transparency.
The above list did not include what happens if you check *both* 8-bit and transparency. Then you get a 16-bit file (8-bit for the color information, and 8-bit transparency). Just open Photoshop and you can see for yourself...?

Basically the "8-bit" checkbox toggles between 8 and 24-bit for the color information, and the "transparency" checkbox toggles an 8-bit transparency channel on/off.
(Edited)
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JEA

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Looks like your probably right.

I sure don't remember adobe making a big deal out of this like one would think they would after people kept asking for this for years and they could make it clear what happens if you check *both* 8-bit and transparency for pngs.
(Edited)
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Jonas M. Rogne

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Ps: Note that when opening an 16-bpp png (8-bit color + 8-bit transparency) image in Photoshop then it will open up as RGB instead of Indexed color mode since the Indexed color mode does not support 8-bit transparency.
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Michael Fahel

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I would really like to see more options with exporting translucent 8-bit PNGs from Photoshop:

- Color palette options (both generated and saved palettes, color limits)
- Limited alpha (16 shades can work well for anti-aliasing vectors at high resolutions)
- Advanced analysis and better delta exports (longer time to save, smaller file size)
- Dithering
- Auto-remove fireflies/noise
- Adam7 Interlacing option

Some of these options are available in Save for Web, but not all (notably, there is no option to control the alpha translucency other than a basic 1-bit on-off). With these features it could be possible to reduce file sizes down to 1/2 or 1/4 of what we're getting with the typical Export As 8-Bit PNG. We regularly upload 4k+ PNGs in limited palettes and it breaks my heart to see all these images uploaded without being properly optimized. I have CompressPNG.com written into our official guides as a workaround to Photoshop's limitations. I regularly get 100-150KB files from that site, some as low as 80 that still look great! Using Photoshop, I regularly get 500-700KB files, some over 1 MB, and they look no better than their CompressPNG counterparts.