html - How is the height of this grid-container being calculated?

Question

In #2, how is the height of .footer being calculated?

#1

.footer {
}

img {
  width: 100%;
}

<div class="footer">
<img src="https://media.istockphoto.com/photos/whole-kiwi-fruit-and-half-kiwi-fruit-on-white-picture-id834807852?k=6&m=834807852&s=612x612&w=0&h=qyouQR9CrIlrPo8FG72PCt1eBV_lTVtnuwVlo9hWZY8=" class="linked-image">
</div>

Answer 1

等待大神解答