Xcode error : Distill failed for unknown reasons

I found that my png was a psd file. I deleted the file and recreated a new png and everything was fine.

grgr

For me, I used with Xcode beta but I didn't upgrade my MAC OSX beta to the latest version as Apple recommends.

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I had the same case as Karsten, one of the image was psd. I opened the file in Mac Preview app and tried to export and found that it was a PSD instead of .png

You might have migrated from a normal project to use an image.catalog. So you can definitely try to copy the bundle resource like launch images. It is so because migrating to an asset catalog for icons and launch images apparently doesn't always add itself to the target automatically.

You can find more on this here & here.

I hope that helps.