Extra image crop focus: face

[crystalenka]

There are some instances where it would be beneficial to crop an image based on the location of a face, instead of from the center. (Author profile pages, for example)

The easiest way is probably going to be to allow someone to sign up for a 3rd-party service like Rapid API (https://rapidapi.com/inferdo/api/face-detection6) and only allow it as an option if there's a valid API key.

The linked Face Detection API is free up to 5,000 requests a month - more than enough for most sites.

They offer sample code for cURL requests.

[nikosdion]

Multiple backend

We can have different backends to the face detection code:

• [ ] RapidAPI Face Detection
• [ ] Microsoft Azure Face
• [ ] AWS Rekognition
• [ ] PHP Facedetect — Really only applies to dedicated servers. I've not seen a host which provides this extension by default.

Having multiple backends is a bit more flexible, especially if the client is already heavily invested in AWS or Azure. RapidAPI is a good solution for sites which don't already use a public cloud. PHP Facedetect is great for advanced and privacy-conscious users who would rather compile and configure a PHP extension than use a public cloud.

Further notes

• All backends can provide information about one or more faces. We will keep the largest / most confident one — depending on which of these two pieces of information the backend provides.
• All backends can provide a bounding box for the detected face (x, y, width, height). This is the data I will be using.
• We need to cache the results keyed by image location and a unique identifier which comes from the image file length and last modified date (so when the image changes we can query its properties again).
• When cropping we will expand/shrink the face's bounding box (from its centre) to match the requested image crop dimensions width and height. This will have the effect on focusing on the face.