gab-social/app/javascript/gabsocial/components/zoomable_image/zoomable_image.scss

.zoomable-image {
  position: relative;

  @include flex(center, center);
  @include size(100%);

  img {
    object-fit: contain;

    @include size(auto);
    @include max-size($media-modal-media-max-width, $media-modal-media-max-height);
  }
}