Export only area of interest into images sequence and reimport back seamlessly

[AndroYD]

Hello,
As illustrated in this picture , I need to export/crop anything that is inside a square mask/area into an image sequence of 512 x 512 pixels, this can be easily achieved by setting the mask in "Add" mode, export all frames into an image sequence at full resolution, batch trim all pictures from the background color and resize them all at 512 x 512 px (it's a perfect square, so it doesn't matter if some pictures were bigger or smaller), however, doing so I lose all position and scale settings (the mask/area is moving/scaling over time) and I can't reposition/reimport them exactly where they were in the original video, of course that wouldn't be a problem if I kept a flat color/transparent background to keep them aligned, but my case scenario is very peculiar, I NEED 512 x 512 pixel pictures because it's the maximum resolution accepted by an external software I use to edit them.
Do you have any ideas/solutions how to achieve this with After Effects or eventually another software? Thanks!

[Rick Gerard]

I would drop the entire comp in or shot (not sure which you are working with) in a new comp and motion stabilize the shot so that the actor's head is not moving in the frame. Once the actors head is not moving you can then pre-compose, change the main comp's frame size to your square image format, position the pre-comp so the actor's head is in the center of the frame, and if needed, add a null to the comp centered on the actors head, parent the pre-comp to the null and add some scale keyframes to smoothly adjust the framing as the actor walks away from the camera.

If all you are doing is adding a graphic to the Actor's head you can do that entirely in AE using Mocha AE's corner pin tracking. It will only take a few minutes. 

It sounds to me like you are very new to AE. If you need more help let us know, but this is actually a very simple first two weeks of the semester project for a new user.

[AndroYD]

Thanks for the answer, I'm sorry but there's been a misunderstanding, I wasn't looking for a method to add a graphics to the actor's head, I asked how I can crop out a square part of a video, export it to an image sequence of 512 x 512 pixels and reimport it back exactly where it was, that modification can be really anything, that picture was just an example of the logic behind it.

[Rick Gerard]

Same technique. Motion stabilize so the actor's head is not moving because that's an easy part to stabilize. Drop the motion stabilized clip in a 512 X 512 comp., add a null right over the actors head, parent the nested comp (original footage) to the null, adjust the position for the first frame and set keyframes for position and scale, move to the last frame and adjust the position and scale for the last frame. 

There you go. All done. Now just export an image sequence and you have your 512 X 512 images and the actor is staying in the frame. Nothing to it.