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TOPIC: Cannot manage alpha channel correctly

Cannot manage alpha channel correctly 3 months, 1 week ago #178867

  • ilmoro
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  • 3 months, 1 week ago
Hi,

I added in a project, on an independent track, a PNG image that I did with GIMP 2.10. This image is partially transparent (using alpha channel) so I added a 2DVE (first) and a Blend (after - adding blend as first create a wrong result) to allow alpha channel to be correctly processed by Lightworks.

The problem is when I set opacity lower than 100%, then I can see the other part of the image which should be completely transparent. The more opacity I remove, the more the borders the program shows.

I tried also to export the image saving and not saving these options in GIMP but nothing changes: save gamma, save background color, save layer offset.

Am I doing something wrong or is it some kind of bug?
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Intel i5 8600K
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Last Edit: 3 months, 1 week ago by ilmoro.

Re: Cannot manage alpha channel correctly 3 months, 1 week ago #178897

  • schrauber
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  • 3 months, 1 week ago
Maybe you just used the wrong effect?
Although the 2D DVE effect uses the alpha channel internally, the output is always Alpha 1 (opaque color).
The 3D DVE Effket passes the alpha values at its output.

However, you should also be able to do without the "blend" effect, and make the mix within the DVE effect and its Opaciti slider. (depending on what you want to achieve).
Mainly automatically translated
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Windows 10, 64 Bit
Intel i5-4440 (3,1 GHz) ; Intel HD Graphics 4600
Last Edit: 3 months, 1 week ago by schrauber.

Re: Cannot manage alpha channel correctly 3 months, 1 week ago #178901

  • jwrl
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  • 3 months, 1 week ago
Adding just the blend by itself shouldn't have created a "wrong result". Do you mean that it didn't handle the transparency correctly, or was there some other problem?
Last Edit: 3 months, 1 week ago by jwrl.

Re: Cannot manage alpha channel correctly 3 months, 1 week ago #178912

  • ilmoro
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  • 3 months, 1 week ago
schrauber wrote:
Maybe you just used the wrong effect?
Although the 2D DVE effect uses the alpha channel internally, the output is always Alpha 1 (opaque color).
The 3D DVE Effket passes the alpha values at its output.

However, you should also be able to do without the "blend" effect, and make the mix within the DVE effect and its Opaciti slider. (depending on what you want to achieve).


Thanks a lot "schrauber", with 3DVE the problem during opacity is no more present and I do not even have to use blend effect.
With 2DVE instead it was not possible to use Alpha Channel without using blend (in the proper rouiting order)
Intel i5 8600K
Asus TUF Z370-Plus
16GB RAM
Sapphire Radeon RX 580 Nitro+ 16GB
SSD
Last Edit: 3 months, 1 week ago by ilmoro.

Re: Cannot manage alpha channel correctly 3 months, 1 week ago #178919

  • schrauber
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  • 3 months, 1 week ago
ilmoro wrote:
... With 2DVE instead it was not possible to use Alpha Channel without using blend (in the proper rouiting order)

You're right.
By setting the Opacity slider of the 2D DVE effect to less than 100%, this effect also shows transparent alpha 0 colors. This is also unexpected for me.
Mainly automatically translated
--------------------------------------------
Windows 10, 64 Bit
Intel i5-4440 (3,1 GHz) ; Intel HD Graphics 4600
Last Edit: 3 months, 1 week ago by schrauber.
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