Bad alpha value in VSE #76437

New Issue

laurent renaud · 2020-05-05T07:39:24+02:00

laurent renaud commented

2020-05-05 07:39:24 +02:00

System Information
Operating system: Linux-5.3.0-51-generic-x86_64-with-debian-buster-sid 64 Bits
Graphics card: GeForce GTX 670/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 435.21

Blender Version
Broken: version: 2.82 (sub 7), branch: master, commit date: 2020-03-12 05:06, hash: 375c7dc4ca
Worked: (optional)

Short description of error
PNG pictures with alpha are wrongly composited in VSE. Same pictures are doing well in Gimp or Blender compositor.

VSE-alpha-problem-files.zip
Exact steps for others to reproduce the error
I can't obtain a "normal" result while compositing png with alpha in VSE. "Normal" is the result obtained with Gimp or blender compositor. VSE look like it makes alpha harder. Can't be solve by any tweaking. I have tried to switch
Alpha source setting to Premultiplied, change color spaces, but still not ok.

I have packed the entire process files.

image-generator.blend : generate the png pictures
Gimp-ok.xcf : png composited ok in Gimp
compositor-ok.blend : png composited ok in Blender compositor
VSE-problem : png wrongly composited in Blender VSE (on the upper left, the good result imported for reference)

Same problem on 2.79/2.81/2.82a/2.83 alpha

Discover that at the end of a project I had to redo my entire VSE editing in Blender compositor to obtain the normal result. Litterally no way out.

Thanks a lot if you can fix it!

**System Information** Operating system: Linux-5.3.0-51-generic-x86_64-with-debian-buster-sid 64 Bits Graphics card: GeForce GTX 670/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 435.21 **Blender Version** Broken: version: 2.82 (sub 7), branch: master, commit date: 2020-03-12 05:06, hash: `375c7dc4ca` Worked: (optional) **Short description of error** PNG pictures with alpha are wrongly composited in VSE. Same pictures are doing well in Gimp or Blender compositor. ![image.png](https://archive.blender.org/developer/F8513380/image.png) [VSE-alpha-problem-files.zip](https://archive.blender.org/developer/F8513384/VSE-alpha-problem-files.zip) **Exact steps for others to reproduce the error** I can't obtain a "normal" result while compositing png with alpha in VSE. "Normal" is the result obtained with Gimp or blender compositor. VSE look like it makes alpha harder. Can't be solve by any tweaking. I have tried to switch Alpha source setting to Premultiplied, change color spaces, but still not ok. I have packed the entire process files. - image-generator.blend : generate the png pictures - Gimp-ok.xcf : png composited ok in Gimp - compositor-ok.blend : png composited ok in Blender compositor - VSE-problem : png wrongly composited in Blender VSE (on the upper left, the good result imported for reference) Same problem on 2.79/2.81/2.82a/2.83 alpha Discover that at the end of a project I had to redo my entire VSE editing in Blender compositor to obtain the normal result. Litterally no way out. Thanks a lot if you can fix it!

laurent renaud commented

2020-05-05 07:39:25 +02:00

Added subscriber: @LaurentRenaud

Campbell Barton commented

2020-05-05 07:54:16 +02:00

Added subscriber: @ideasman42

Campbell Barton commented

2020-05-05 07:54:16 +02:00

Changed status from 'Needs Triage' to: 'Needs User Info'

Campbell Barton commented

2020-05-05 07:54:16 +02:00

This report is missing:

Last version that worked.
Exact steps to redo the error.
A blend file (unless the steps start from the default startup).

This report is missing: - Last version that worked. - Exact steps to redo the error. - A blend file (unless the steps start from the default startup).

laurent renaud commented

2020-05-05 08:35:31 +02:00

Changed status from 'Needs User Info' to: 'Needs Triage'

laurent renaud commented

2020-05-05 08:37:38 +02:00

In #76437#924449, @ideasman42 wrote:
This report is missing:

Last version that worked.

Exact steps to redo the error.

A blend file (unless the steps start from the default startup).

Sorry, I thought it have to be done on the next page...

> In #76437#924449, @ideasman42 wrote: > This report is missing: > > - Last version that worked. > - Exact steps to redo the error. > - A blend file (unless the steps start from the default startup). Sorry, I thought it have to be done on the next page...

Richard Antalik commented

2020-05-05 13:38:00 +02:00

Changed status from 'Needs Triage' to: 'Confirmed'

Jeroen Bakker commented

2020-05-19 10:31:40 +02:00

Added subscriber: @Jeroen-Bakker

Jeroen Bakker commented

2020-05-19 10:31:40 +02:00

In the provided files the VSE colorspace is set to sRGB. Compositor uses Linear color space. In the color management panel you can select which colorspace to use for the VSE.
There is still a difference, that is related to the view transform that have been set in the image-generator.blend. The compositing does alpha compositing before the view transform. The vse test does the view transform before saving the image and after the vse.

See here for a better comparison.

#76437.blend

In the provided files the VSE colorspace is set to sRGB. Compositor uses Linear color space. In the color management panel you can select which colorspace to use for the VSE. There is still a difference, that is related to the view transform that have been set in the `image-generator.blend`. The compositing does alpha compositing before the view transform. The vse test does the view transform before saving the image and after the vse. See here for a better comparison. [#76437.blend](https://archive.blender.org/developer/F8542746/T76437.blend)

Jeroen Bakker commented

2020-05-19 11:16:45 +02:00

Changed status from 'Confirmed' to: 'Archived'

Jeroen Bakker closed this issue

2020-05-19 11:16:45 +02:00

Jeroen Bakker self-assigned this 2020-05-19 11:16:45 +02:00

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Bad alpha value in VSE #76437