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I have a PNG-8 image with transparency, which, due to this problem, I cannot edit in Photoshop (CS5).

Is there a tool that would convert PNG-8 back to PNG-24, preserving transparency layer, so that the file will open correctly in Photoshop?

(The other way to deal with that problem would be to capture a screenshot of any browser displaying that PNG-8 file correctly - but then it would be necessary to induce the transparency layer back, which I'm not sure how is done.)

Sample of PNG-8 image

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I don't know of any specific tool for that purpose, but I do know that with GIMP you can open the PNG8 and change the colorspace using the menu path Image->Mode->RGB. Unfortunately I do not have Photoshop to test if the new file is openable myself, however I've provided a version of the sample you provided where the colorspace has been changed so you can give it a try.

https://docs.google.com/open?id=0B6Ad3OCQFyOINmMyOGE0ZmEtMDhjOC00OTZmLWE4M2EtYTYzZmJlZjMyNTA0

  • Needed this exact same file... thx from the future! ;) – luckykind Oct 7 '11 at 17:27
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Photoshop displays transparency wrong: You've got PNG8 with alpha not supported by Photoshop. For editing, keep PNG in 24-bit, and convert to PNG8+alpha only when done. You can convert PNG8 to 24-bit by resaving it in Preview.app, Fireworks or with: pngout -s1 -c6 -force file.png

The answer comes from http://calendar.perfplanet.com/2010/png-that-works/ under the troubleshooting heading.

I also created a YouTube video to show the process at http://www.youtube.com/watch?v=aCO37zYhEp0.

  • Thanks, Nick - already re-saved with GIMP from the above answer, but pngout may be a more optimal solution. – Igor Apr 7 '11 at 7:19
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For a scriptable/command line solution:

After installing GDAL Python Tools (on Linux apt-get install python-gdal)

pct2rgb.py -of PNG -rgba PNG8.png PNG24.png

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