Show whole image and centre it

<!-- HTML -->
<div class="big-img-container">
  <img src="..." alt="Large image">

/* CSS */
  .big-img-container {
    display: flex;
    position: fixed;
    left: 0;
    top: 0;
    right: 0;
    bottom: 0;

  .big-img-container img {
    object-fit: contain;
    max-height: 100%;
    max-width: 100%;
    display: block;
    margin: auto;

How does this work? The big-img-container limits the frame of the image to the size of the browser window. The property-value pair object-fit: contain makes the magic happen. This scales the image down while maintaining the original aspect ratio. This means that there’s no stretching of the image. The max-height and max-width properties ensure that the img doesn’t break out of the area defined by the big-img-container. Finally, the good old display: flex and margin: auto combination put the img in the center of the screen. Altogether, these few lines of CSS form the basis of a nice centred image effect.

Color scheme: