Why are PNG-8 files mangled when opened in Photoshop?

Posted by Daniel Beardsley on Super User See other posts from Super User or by Daniel Beardsley
Published on 2010-06-12T02:56:31Z Indexed on 2010/06/12 7:33 UTC
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image

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adobe-photoshop

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graphics

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png

Why are some 32 bit PNGs opened in Photoshop with Indexed Colors and no transparency?

For instance, I grabbed a png icon file of the Stack Overflow logo at: http://blog.stackoverflow.com/wp-content/uploads/icon-so.png When opening it in Photoshop CS3, it apparently treats it as indexed color and gets rid of the alpha channel. The image on the right is a screen grab of the icon. Changing the Image mode in Photoshop to RGB doesn't change the image at all. I've tried this with a few other PNGs and it seems hit or miss.

When viewed in other programs, it displays fine.

left:png opened in Photoshop, right:screen grab of png from browser

What gives?, does Photoshop not interpret the PNG file format correctly?

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