So, I started an iMovie project and I imported a couple pictures. I used iPreview to remove the white from the background, and then imported it into iMovie. I used the picture in picture option to place it on the video. Now the top and bottom is cut off, and whenever I click on fit, a black background appears. Is there a way to fully show the picture, but keep the transparent background?
MacBook Pro
I am not sure what exactly you are doing in Preview, but a couple of notes may help you.
You can import photos into iMovie with Alpha Channel (for transparency).
The photo should be edited to be in the same aspect ratio as the movie (e.g. 16:9 aspect ratio or 1920x1080 pixels for example.)
The photo should be saved as a PNG for the Alpha Channel to work.
If you apply a FIT or CROP to a PNG in iMovie, it will be converted to a JPEG and you lose the Alpha Channel. This is why you set up the correct aspect ratio to begin with. When you lose the Alpha Channel you get a black background rather than the transparent background.
iMovie Picture Help
