Is it possible to open iOS camera and use as canvas from a web app?

Background

• Interested in machine learning / computer vision
• Would like to build a real-time object detection app for fun to learn

Requirements

• Need to develop for the web and use on mobile (i.e. develop for the web and use on at least iOS, Android is a +)
• Need to access camera from a mobile device (desktop not required but is a +)
• Need to be able to use the real-time camera view as a canvas so I can draw rectangles around the objects in the view

Technologies

• Other than being a web app, I have no real restrictions here

Questions

• Is it possible build a web app and access a camera on iOS without actually taking a photo/video for a file input? (I've done some previous research and it seems to open the camera, you basically need to use it for file upload to an HTML input)
• Is it possible to use that camera view as a canvas and draw on it?