Outlining an image in a photo

TscienceK wrote:

I'm trying to get the image of a person outlined to separate him from the other person in the photo.

I order to do that, you need a photo editing app in which you can select a specific, nongeometric area of the image. Here are a few suggestions:

• In Photoshop that can be done with the Quick Selection tool or perhaps the Magic Wand tool.
• Pixelmator has a similar Quick Selection tool. Here is a brief video showing how it works.
• Affinity Photo has a Selection Brush tool that works similarly.
• Certain other photo editing apps have similar tools, however Apple Photos does not.

Assuming you mean a photo displayed on your screen, grab a screenshot:

Do Shift-CMD-5 then move/resize the resulting outline to fit the photo you want to save (extract), then hit Return. The selected portion of the screen (photo) will be saved to your desktop. The default format is PNG.

You will likely need a third-party image tool that has more smarts about extracting an image from a photo than is available in existing macOS or iOS solutions. Especially if there is color similarities between the background and the desired image for extraction.