Image resize before upload from mobile to website/database/server

Hi there, I have just ran into my clients requirement of uploading multiple pics right from their mobile regardless of the make. I have made website and database for the same but through php, i can only resize the pics once they are uploaded to the server as the script runs after that. I need someone with this expertise to build something which I can integrate with the website form to resize the snaps right before they can upload to website. Justs like whatsapp. As it also converts large image size into 100-200Kbs so they can upload multiple snaps at the same time with the help of 2G connection where internet speed is very slow. Awaiting suggestions and i need it to be done ASAP. Please quote economical as all this is extra work for me regardless of asking more from my client. Thanks in advance!