Is there any way to save a PNG-8 file with Alpha Transparency in Photoshop?

Question

I recently discovered something that I previous thought was impossible: PNG-8 files can store Alpha Transparency in the same way as PNG-32 files can. Not Indexed Transparency (like GIFs), but full on Alpha Transparency.

(You can learn more about this here: http://blogs.sitepoint.com/png8-the-clear-winner)

Apparently it's possible to do this using Fireworks, but I can't find a way to do it using Photoshop.

Does anyone know a way of enabling this incredible feature in Photoshop? Through add-ons or by any other means? It's so incredibly useful for web developers that I can't believe it's not been included in the latest version (or any version) of PS!

Solution 1

An updated answer for 2015 tech.

I'm using Photoshop Creative Cloud 2015 (for PC, I don't know if there is any difference on Mac) and there is a choice to

"File > Export > Export as"

There aren't a whole lot of options to adjust from here, but if you select PNG-8 format it will automatically use full (or what appears to be full) alpha transparency in a PNG-8 format. Mileage may vary depending on image size and number of colors as to whether or not the result will actually be smaller than a regular PNG-24. On average the images I have been working with have resulted in about 1/3 final file size when compared to a PNG-24 of the same image.

NOTE: Check that the image mode is NOT indexed (lock icon on the layer) as I was not able to get the alpha transparency to work otherwise. I used RGB mode with successful results.

Solution 2

You can use Ethan Gardner's pngquant script to convert a photoshop file to alpha-tx PNG. It works on Mac and PC. http://www.ethangardner.com/articles/alpha-transparency-in-png-8-images-without-using-fireworks/

Solution 3

Not that I know of, but save the image as PNG-24 then use this:

http://compresspng.com

(I tried http://www.8bitalpha.com and http://tinypng.org but they gave me poor results.)

Solution 4

This is an important subject, especially for web design. A big png24 image can be ~1mb, almost impossible to consider for web site design use. But same image as png8 with alpha is ~250kb, ok in a lot of situations.

And finally a drag-and-drop solution for png8 with alpha transparency, free as of 2013 04: http://tinypng.org/

And some more related tools are here: http://pngquant.org/

Enjoy!

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Comments

[Ignacio Vazquez-Abrams]

Photoshop and PNG-8 hate each other. Just thought you should know.

[Django Reinhardt]

Yes. Those options are for indexed transparency. My question was about alpha transparency.

[Django Reinhardt]

This may be the best option available today. Such a shame, but thanks.

[Django Reinhardt]

Seems a lot slower than 8bitalpha and tinypng, but good for control, thanks.

[Django Reinhardt]

Yes, it's far from perfect (and seems slower), but it's sort of there. I hope Adobe finally improves this soon.