How would I add an outline / border around this image?

Question

I have a vector of a few unicorns that is currently on a blue background:

I want to put them on a white background, but when I do that, the unicorns lose their shape because they are white and don't have an outline:

How would I add a border / outline to them without having to draw it myself?

I'm looking for methods related to Photoshop, Sketch, or Illustrator.

Answer 1

In Illustrator...

Group the Unicorn if it's not already a group.

Then in the Appearance Panel add a new stroke to the group. Click and drag the stroke in the Appearance Panel, so that it is below the <Contents> item in the panel.

You'll then have a stroke around the entire group which you can adjust.

_{(Old screenshot... but the panel isn't really that different today.)}

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Photoshop : Layer Style > Stroke will add a stroke around an entire layer or smart object layer. Although, for vectors using Illustrator or Sketch is probably better.

Answer 2

I think this is not possible, because the border of the unicorn is white in color and cannot be white. You can find places that offer unicorn images with black borders.