A "self-border" using multiplication and transformation

We want to achieve an effect that used the image itself to create a semi-transparent border. The result will look similar to the picture below:

The basic idea of the solution looks like the following:

Here an important functionality is utilized that is also crucial for the creation of many other complex effects: Multiplication.

To achieve 2. at all a copy of the original image needs to be stored to be able to overlay the image that might already be changed by previously assigned sub-effects. The multiplication effect allows exactly this. By using it the normally flat list of effects will become a tree, because the multiplication effect can have child elements. The sub-effects can be moved around via drag&drop.

All effects that are children of the multiplication effect are "served" with that state of the image data source that has been current at the branching point, no matter in which way and how much a different child element has changed the image.

Here you see the completed effect: The multiplication effect got a transformation assigned as sub-effect that enlarges the image by a few millimeters. To that the transparency effect is assigned to make the image semi-transparent.

Now we need to use a little trick: To display the original image again we simply add a second transformation to the multiplication. Only this time no offset, rotation, etc. is set. So the image stays the same.

Note: Child elements of multiplication effects can have child elements themselves.