Semi-transparent color problem in Prores export

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Principle Version: 5.14
macOS Version: 11.1
Sketch Version: N/A
Description of what you need help with:

How to export transparent videos from Principle to be used in Final Cut Pro. There appears to be a bug in the export, so that semi-transparent pixels are darker in the export than they were in the Principle document.

Steps to reproduce the behavior:

  1. Create a principle document with some semi-transparent elements e.g. rects with fill (255, 255, 255, 0.5)
  2. Set the artboard fill to transparent
  3. Make a short recording
  4. Save as Prores
  5. Check the colors in output

Screenshots/Sketch File/Principle file: (if applicable)
example document:

example export:


Note that the white squares become grey. The black seems unaffected.

The same problem can be seen when importing the prores file into Final Cut, which is the workflow I’m trying to use.

I wonder if it was a problem with alpha premultiplication during the export?

You can also see this bug as black fringing around anti-aliased graphics when doing a transparent export.

I’ll attach the principle document I’m using, and the prores file I exported.

Transparency bug.mov


By the way, thank you so much for Principle! It’s a really great bit of software, I absolutely love using it :slight_smile:

I’ll look into this. alpha premultiplication does seem like a possibility.

1 Like

Hi there. Just a note that I’m still seeing this bug in the latest version, even since the Apple Silicon ProRes fix. In the latest macOS, Quicklook now composites transparent videos onto black, so it’s not so easy to see the alpha channel. Importing it into Final Cut still reveals the transparency however.

@joerick Hey Joe, sorry for the delay on this.

I made it so that Principle tags ProRes video as having premultiplied alpha. That makes it appear correctly in Final Cut Pro X. Should go out in the next version: 6.20

2 Likes

Brilliant, thanks! I look forward to it :slight_smile:

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@joerick You can give this beta version a try. If you find any issues with it, please create a new topic in this forum. https://principleformac.com/download/Principle_6_20_beta_1.zip