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Doing some design for 3D and developers need PNGs with RGBA8 for transparency. I am not even sure if this is possible with png. When I look at channels I see no alpha channel but there is alpha on the png, which is very confusing.

My flow is usually through generator, so I name layers fileName.png32 so it does full alpha but they turn out wrong and I have to open them and resave and that fixes it somehow (though I still cannot see alpha channel).

edit: more details. Here are the actual error I get from the program trying to import the PNG.

MakeImageCompatible: Converting Image 'item url here' from TEXFMT_BGR8 to TEXFMT_BGRA8

so its saying somehow it cannot read the alpha channel from what I gather.

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  • The layer transparency within Photoshop is the alpha, there's no separate specific channel for that alpha.
    – Scott
    Commented May 7, 2014 at 23:34
  • so guess the question remains, does png even support RGBA8, or would I have to use something else like tiff or tga?
    – wutronic
    Commented May 7, 2014 at 23:58
  • Yes PNG32 = RGBA. Saving a file which contains layer transparency in Photoshop as PNG24 results in a PNG32 image. It is slightly convoluted since there's no specific reference to PNG32 within Photoshop.
    – Scott
    Commented May 8, 2014 at 0:03
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    I really do not understand... "naming layer filename.png32 forcing it to go 32" Names have never "forced" Photoshop to do anything in terms of formats.
    – Scott
    Commented May 16, 2014 at 0:57
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    Thanks for the info! Both files are perfectly fine PNGs (according to pngfix-32; no errors or warnings whatsoever). Closer examination shows that their IDATs (duh ;}) and some pixel values (may be caused by color management) differ. Besides that, the first has additional 5 chunks defined, that the second file is missing: bKGD, cHRM, gAMA and 2 text. The first of them declares the background color, so my guess is it could be misinterpreted by some half-baked PNG decoder. More could probably be said if we know some more details about the target app.
    – thebodzio
    Commented May 16, 2014 at 14:24

2 Answers 2

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Is it possible to export RGBA PNG from Photoshop? Very much so!

As Scott said, there's no separate “alpha” channel visible in “Channels” panel, but the alpha channel is there anyway (just not “shown” in the panel), as long as the image doesn't have the “Background” layer. Anyway this alpha channel is used when PNG files are saved. If you need some more control over your PNG files saved by Photoshop, I recommend you to use the “Save for Web”.

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For anyone else trying to get Photoshop to export correct alpha to a PNG file without modifying the RGB channels of pixels with non-opaque alpha, a good solution is the open-source plugin SuperPNG: https://www.fnordware.com/superpng/

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  • The conept is alien to greahic designers, adobe uses quite a lot of effort in their designs to keep people from understanding that there are 2 ways to deal with alpha and that transprent pixels would be other than tranparent. But essentially it used to be possible to set an option like 2 years back to do it but they have removed it.
    – joojaa
    Commented Aug 18, 2022 at 8:08

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