Custom UI icons appear compressed, pixelated

We’ve found loading custom icons into the Unreal Editor (that represent buttons for in-house tools) always look compressed or pixelated.

We’ve tried to copy the format & size of default icons in the Editor, but are not getting a clean, anti-aliased look, like the original images created in Photoshop.

Is there any information on file spec, compression, etc for creating custom icons in Editor to fix this issue?