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TIFF: Potential Issue with (Premultiplied?) Transparency

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Hi there,

 

I noticed a potential problem with (premultiplied?) alpha/ transparency in some TIFF files.

 

For example loading "Install OS X El Capitan.app/Contents/Resources/ProductPageIcon_512x512.tiff" (Sorry, I can't attach the original file to this report for obvious copyright reasons ;) ) shows the typical and unwanted black halo pixel effect in Affinity Photo. OS X's own Preview.app displays the very same file properly, see attached screenshot.

 

 

I'm not entirely sure this is a bug in Affinity or not. In case it isn't I would appreciate a tip how to fix this problem when it happens. :)

post-17131-0-46911500-1451129602_thumb.png


3D and 2D hobby(art)ist. You can follow me on Twitter: @binaryriot or Instagram: binaryriot

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I am having an issue with this too. In photoshop there are a couple options to "remove white matte" or "remove black matte". I think this is basically adding or remove premultiplication. The particular image I'm trying to open has a white halo when placed on a black background. this is removed in photoshop with the "remove white matte" option. But I don't think there is an option in affinity.

post-27784-0-93374400-1456411274_thumb.png

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OSX preview filters the result initially.

 

Try resizing the window and see if it then resamples with nearest neighbour.  I've seen this when looking into PSD preview in Finder.  After resizing the preview or Finder window, the preview image gets resampled and shows pixelation.  Does it then show the black edging?


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@Ben:

 

OS X's Preview does handle the file in question correctly in any case. Yes, it gets somewhat pixely during the resize operation (some speed-up thingy, I guess), but the end result is fine (at any scaled size). It never produces a black halo (like Affinity Photo).

 

I also tried the file in Notes and Safari and it looks good there too. So just Affinity Photo does something fishy. :) 


3D and 2D hobby(art)ist. You can follow me on Twitter: @binaryriot or Instagram: binaryriot

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