If you want to blur the edges of a photograph in Pages, Numbers or Keynote (macOS or iPadOS) the Keynote presentation available from the link at the foot of this article will assist you.
The presentation has three (3) Image Styles that are not usually available in a Keynote presentation. Any or all of these can be copied to your own documents. Instructions are available in the Keynote presentation.
You can see what I have called ‘blurred edges’ applied to the image within the presentation making the selected image look like this:
It is possible to copy the Image Style to any other Pages, Numbers or Keynote document and apply it to any images such as photos. in that document. It gives the image a Border > Picture Frame and the Size can be adjusted to adjust the ‘blur’ effect.
The Keynote presentation (as a .zip file) is available after you have logged in here: https://ausom.net.au/download/ausom-image-styles/
I am happy to answer questions via email.
Pam Doughty: firstname.lastname@example.org