How can I make a page hero image move on page load?

Question

I have a banner image loading on my site with this code:

@keyframes animatedBanner {
  from {
    background-position-y: bottom;
  }
  to {
    background-position-y: top; 
  }
}

.page-hero {
  background-image: url(https://via.placeholder.com/428x100);
  background-repeat: no-repeat;
  padding-top: 214px;
  padding-bottom: 214px;
  text-align: center;
  animation: 2s ease-out 0s 1 animatedBanner;
  background-size: auto;
}

 <div class="page-hero">
    <div class="inside-page-hero grid-container grid-parent">
        <h2>this is an image</h2>
    </div>
</div>

This does what I hoped it would (slide the image up when the page loads). But the problem is that I was hoping to have the image span the entire width of the screen regardless of width. I tried using cover, but then the image doesn't scroll at all.

Is there a way to make this design responsive on the image?

Answer 1

background are a bit tricky when it comes to animate the position. You need some specific sizes. I have a detailed answer (Using percentage values with background-position on a linear-gradient) explaining the logic behind the values I am using:

@keyframes animatedBanner {
  from {
    background-position: 50% 200%;
  }
  to {
    background-position: 50% 50%; 
  }
}

.page-hero {
  background-image: url(https://picsum.photos/id/1068/800/400);
  background-repeat: no-repeat;
  padding:100px 0;
  text-align: center;
  animation: 2s ease-out animatedBanner both .5s;
  background-size: auto 200%;
}

<div class="page-hero">
    <div class="inside-page-hero grid-container grid-parent">
        <h2>this is an image</h2>
    </div>
</div>

To get the opposite direction

@keyframes animatedBanner {
  from {
    background-position: 50% -100%;
  }
  to {
    background-position: 50% 50%; 
  }
}

.page-hero {
  background-image: url(https://picsum.photos/id/1068/800/400);
  background-repeat: no-repeat;
  padding:100px 0;
  text-align: center;
  animation: 2s ease-out animatedBanner both .5s;
  background-size: auto 200%;
}

<div class="page-hero">
    <div class="inside-page-hero grid-container grid-parent">
        <h2>this is an image</h2>
    </div>
</div>

And if you want to avoid the complexity of background-position and background-size, use pseudo-element

@keyframes animatedBanner {
  from {
    transform: translateY(100%); /* or -100% */
  }
}

.page-hero {
  padding: 100px 0;
  text-align: center;
  position: relative;
  z-index: 0;
  overflow: hidden;
}

.page-hero:before {
  content: "";
  position: absolute;
  z-index: -1;
  inset: 0;
  background: url(https://picsum.photos/id/1068/800/400) center/cover;
  animation: 2s ease-out animatedBanner both .5s;
}

<div class="page-hero">
  <div class="inside-page-hero grid-container grid-parent">
    <h2>this is an image</h2>
  </div>
</div>