Resize and reposition preview based on picture extend by frame

[fmiccolis]

Prerequisites checklist

• [x] I have read the contributing guidelines.

What is the purpose of this pull request? (put an "x" next to an item)

• [ ] Documentation update
• [ ] Bug fix
• [x] New feature
• [ ] Other, please explain:

What changes did you make? (Give an overview)

In a previous feature I give the opportunity to the user to visualize the picture frame or the collage frame during the live preview. At the time there wasn't the possibility to extend the picture by the frame setting up the percentages in left, top, right and bottom. I created this feature to replicate what the user will see as a finished picture with frame applied during the live preview to better position himself during the countdown.

Is there anything you'd like reviewers to focus on?

I want the reviewers to focus in general on the code because it's been a long time since I coded the photobooth project

[andi34]

No stale. Look at next days.