Hi;
I made a quite similar project, which is in my references: https://www.freelancer.com/projects/php/Very-simple-website-modification/
Though its simplistic, working with GD or Imagemagick like image generation libraries can be tricky. I'm quite skilled on image generation on the fly, as I worked on many projects like this, including some photo kiosk in my country.
Please feel free to ask questions and have a look at my skills,exams I passed and my testimonials.