How/Where to do initial setup of application - image loading

[sww1235]

I have some data structs that are loaded via serde and contain SVG data inside them. As I need to display all the images found, I loop through all maps within them and load the images.

Right now, this is happening within the rendering process, which means it runs once a frame. Now I know the images are cached in theory and are not reloaded every frame but the looping through maps in theory still runs.

What is the best way to only run this code at application start or on demand?