Setup AEM to use the worker

Go to your AEM Cloud instance and open Tools -> Assets -> Processing Profiles and then create a new processing profile, e.g. My Worker test profile. On the Custom tab, configure your renditions to use your worker, as shown below.

I configured 3 renditions using following imgix configuration params (we don't need to escape JSON if it's used in AEM)

Crop an image to 300x300 px around faces if detected, or around busy sections of the image (entropy).

{
  "fit": "crop",
  "crop": "faces,entropy",
  "w": 300,
  "h": 300
}
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{
  "fit": "crop",
  "crop": "faces,entropy",
  "w": 300,
  "h": 300
}

Same as the previous, but additionally apply an ellipse mask around the cropped area.

{
  "fit": "crop",
  "crop": "faces,entropy",
  "w": 300,
  "h": 300,
  "fm": "png",
  "mask": "ellipse"
}
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{
  "fit": "crop",
  "crop": "faces,entropy",
  "w": 300,
  "h": 300,
  "fm": "png",
  "mask": "ellipse"
}

The last one is similar to the first, but this time we add a text watermark to the image.

{
  "h": 300,
  "w": 300,
  "fit": "crop",
  "crop": "faces,entropy",
  "mark": "https://assets.imgix.net/~text?w=200&txt-color=fff&txt=Hello+world&txt-size=16&txt-lead=0&txt-pad=15&bg=80002228&txt-font=Avenir-Heavy"
}
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{
  "h": 300,
  "w": 300,
  "fit": "crop",
  "crop": "faces,entropy",
  "mark": "https://assets.imgix.net/~text?w=200&txt-color=fff&txt=Hello+world&txt-size=16&txt-lead=0&txt-pad=15&bg=80002228&txt-font=Avenir-Heavy"
}