Setting color around images to black on mobile

Custom CSS & Theme Design
1

What I’m trying to do

Is there a CSS snipet to set the color around a png to black on mobile devices? When tapping on an image, I would like to see:

1
11131×1491 212 KB

Not

2
21290×2796 112 KB

Things I have tried

I’m still an obsidan novice, but tried several codes that appeared close to my problem, but no luck. Apologies if i missed somethnig obvious. Thank you for the look.

2

Oh my god, after checking every possible class in Obsidian app.css file, I’ve managed located the correct class. :sob:

.mobile-image-viewer {
    background: white;
}