Greetings from Chiang Mai! I'm ready to work on this.
I've done very similar tasks in the past, that is, wrapping ffmpeg in a bash script with, basically, conversion shorthand "macros". Previous related freelancer.com project at: https://www.freelancer.com/projects/linux-shell-script/ffmpeg-video-conversion/
Considering your required skills being "PHP", I assume you mean to call this from a PHP script.
Please review below assumptions and scope. Let's discuss in PM.
Assumptions:
- host machine has ffmpeg and all required libraries installed
- Script language is PHP
- Input file is an image
- PHP allows system shell execute
- Input path(s) are readable, output path(s) are writable
Deliverable:
Standalone class with methods
- construct: initialize and set defaults
- zoompan: execute zoom and pan
- Arguments: input file path 'f', zoom level 'z', horizontal position 'x', vertical position 'y', output file name 'o'