How Do I Create An Alpha Channel on this Image?

[ScotWoody]

I am using this in a video editing programme to view a small video though it.  There is a background image and much smaller videos on top.  Then I will be applying the attached image.

This is how it should work:  The white area will be replaced by the video.  The rough edging will encroach onto the video - that's what I want.  The black area should take on the format of the underlying image.  I should be able to select Alpha channel in the video editing program and this should happen.  However, on my image if I select Alpha it doesn't work - it just turns everything black. 

If I adjust some of the other settings and ignore Alpha it more or less works ie the video replaces the white section.  But, it only works if there is a black background, if it is the background I want to have then I see the black as black rather than it taking up the colours of the underlying image.

I think I'm not creating an Alpha channel on my image.  I have now spent several days trying to work out how to do this and have looked at some of the forum answers but I can't seem to make them work. 

I have attached a sample - it should look like the image on the left which uses an alpha channel.  Mine is on the right and this is how mine appear.s

Can anyone help?

 

Edited December 27, 2024 by ScotWoody

[GarryP]

Welcome to the forums @ScotWoody

I’m assuming that you are using Photo and not Designer or Publisher.

First go to menu “Document” and check (tick) “Transparent Background”.

Then use menu “Filters → Colours → Erase White Paper”.

Then export to a file type that can include transparency, for example PNG.

That should so what you want, unless I’ve not understood your requirements properly.

[ScotWoody]

Thanks GarryP that has worked perfectly.  Simply when you know how 😉

29 minutes ago, GarryP said:

Welcome to the forums @ScotWoody

I’m assuming that you are using Photo and not Designer or Publisher.

First go to menu “Document” and check (tick) “Transparent Background”.

Then use menu “Filters → Colours → Erase White Paper”.

Then export to a file type that can include transparency, for example PNG.

That should so what you want, unless I’ve not understood your requirements properly.

 

[GarryP]

You’re welcome.

It’s just a matter of knowing what things are called and where they are, and sometimes that’s half the battle.