Transparency lost when using add operation in mask, it's a bug?

What is your operating system?
Windows 11 family 22H2

What is your Shotcut version (see Help > About Shotcut)?
Shotcut 23.06.14 but same behavior on 23.07

Can you repeat the problem? If so, what are the steps?
when i use many mask simple shape and a mask apply on a clip and try to add a text or a transparent on a second track the transparency do’nt work, the add operation break the transparency
see the problem in video here :

I do something wrong or it’s a bug ?

Please improve the subject line. Otherwise, people (including developers) will probably overlook it as useless when scanning through the list in the category at a later time. We are rarely going to try to fix a problem as soon as we read about it.

The problem is that Mask:Apply does not reset the alpha channel. That might be a feature for some, but a bug for others. You can see that by hiding V2 and adding a Alpha Channel: View after the Mask: Apply. The, track blender - by design - combines the alpha channels of each video track. The reason the Operation: Add makes a difference is because the Mask filters take a snapshot of the input image to be used with Mask:Apply, and the second Mask: Simple Shape’s input image includes an alpha channel. With the alpha channel view applied, you can toggle the second Mask: Simple Shape filter to see what I mean. The blender in Mask: Apply is alpha-combining as well.

The workaround is to reset the alpha channel on V1 after the Mask: Apply (or on the track) by adding an Alpha Channel: Adjust with Mode = Threshold, Amount = 100%, and Invert ON. I will add a Reset mode to this filter for the version after the next.


understood :slight_smile:

This Mode option was added in version 12.09. However, it clears the alpha channel to all transparent. You still need to click Invert to make it all opaque.

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