Responsive Image Gallery With Animated Captions

Responsively resizing images is a common need, and modern CSS provides tools for ensuring a consistent aspect-ratio while not distorting the images. And grid gives us flexibility for a gallery layout as well as positioning multiple elements in a shared space.

This responsive gallery technique explores using:

  • object-fit for responsive image scaling
  • aspect-ratio for consistent image sizes
  • A CSS Grid trick to replace absolute positioning
  • CSS transforms for animated effects
  • handling for touch devices
  • respecting reduced motion

Here is our initial HTML, which is an ul where each li contains a figure with the image and figcaption:

<ul class="gallery" role="list">
<li>
<figure>
<img alt="" src="https://picsum.photos/550/300" />
<figcaption>Candy canes ice cream</figcaption>
</figure>
</li>
<li>
<figure>
<img alt="" src="https://picsum.photos/400" />
<figcaption>Ice cream biscuit</figcaption>
</figure>
</li>
<li>
<figure>
<img alt="" src="https://picsum.photos/600/450" />
<figcaption>Cream biscuit marzipan</figcaption>
</figure>
</li>
</ul>

What's that role="list" doing there? It ensures assistive technology still interprets the element as a list after we remove list styling with CSS.

I've used different image sizes both to showcase how object-fit works in terms of fitting its container, and also to lessen the chance of duplicate images from the picsum service.

Note that due to using a random image service, I haven't provided full alt descriptions or real figcaption text for these demo images. Ideally you should write alt that describes the image, and use figcaption to provide context for the image as a figure. I recommend this resource to learn more about the importance of writing alt and figcaption.

Since we've used a list, we need to remove default list styles, and we will also set the list up as a grid container. These initial styles achieve placing our list items in a row and ensures the images stay in their grid columns but does not resize them.

CSS for "gallery class"
.gallery {
list-style: none;
padding: 0;
margin: 0 auto;
display: grid;
grid-template-columns: repeat(auto-fit, minmax(20ch, 1fr));
gap: 1rem;
}

.gallery img {
display: block;
width: 100%;
}

If you're like me and have tried to do this in years past, you probably threw your rollerball mouse across the room trying to figure out why position: absolute wasn't playing nicely with your jQuery animations.

CSS Grid and CSS transforms are here to save the day! ๐ŸŽ‰

We're going to setup the figure to use grid display, and also define a custom property to hold the desired image height. And we'll give it a background in case the image is a little slow to load.

CSS for "Base figure display styles"
.gallery figure {
--gallery-height: 15rem;

/* reset figure default margin */
margin: 0;
height: var(--gallery-height);
background-color: hsl(200, 85%, 2%);
}

Next, we apply object-fit to the image along with width: 100% and pull in the custom property for the height so that it scales to the size of the figure. The magic of object-fit: cover is that no distortion occurs.

CSS for "Image display styles"
.gallery img {
display: block;
width: 100%;
object-fit: cover;
height: var(--gallery-height);
}

If you resize the demo, you'll see that the img is now behaving much as if it were applied as a background-image and using background-size: cover. The img tag is acting like a container for it's own contents.

For a helpful intro to object-fit for responsive image scaling, check out this earlier post from this series. You might also like my 3-minute free egghead lesson on object-fit.

We can improve the image sizing by upgrading to using aspect-ratio when supported using the native CSS feature @supports. When it is supported, we'll drop the height and swap for defining the aspect-ratio to use. This allows us to have more consistently sized images across viewports.

CSS for "Use aspect-ratio with @supports"
/* Add aspect-ratio custom property */
.gallery figure {
--gallery-aspect-ratio: 4/3;
}

@supports (aspect-ratio: 1) {
.gallery figure,
.gallery img
{
aspect-ratio: var(--gallery-aspect-ratio);
/* Remove height to prevent distorting aspect-ratio */
height: auto;
}
}

Positioning the Caption

Now at this point, the caption has flowed naturally according to DOM order below the image. This is also due to default CSS grid behavior because it's assumed that it should be in its own "cell" and by default grid items flow down the y-axis in rows.

To resolve this, we create a named grid-template-areas for the figure, and assign both the img and figcaption to live there. Then, we'll use grid positioning to set place-items: end on the card to move the caption to the bottom right of the "cell".

CSS for "Styles to position the figcaption"
.gallery figure {
/* ...existing styles */

display: grid;
grid-template-areas: "card";
place-items: end;
border-radius: 0.5rem;
overflow: hidden;
}

.gallery figure > * {
grid-area: card;
}

.gallery figcaption {
transform: translateY(100%);
}

You may notice the caption is also no longer visible, partly from adding overflow: hidden to the figure. Then to place the caption, we used CSS transforms to set the initial position outside the figure. A value of 100% for translate will move the element 100% relative to the axis it's placed on. So, translateY(100%) effectively moves the caption "down" out of the initial view.

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Animating the Caption

Our animation will trigger on hover, and we want it to smoothly animate in and back out again. This requires setting up the transition property.

We'll define that we expect a transition on the transform property, and that the transition duration should be 800ms and use the ease-in timing function.

The :hover styles will actually be placed on the figure since it is the containing element, so we'll also add a transform definition that moves the caption back to it's inherent starting point by returning it to position 0 on the y-axis.

CSS for "Style and animate the figcaption"
.gallery figcaption {
transform: translateY(100%);
transition: transform 800ms ease-in;

/* Visual styles for the caption */
padding: 0.25em 0.5em;
border-radius: 4px 0 0 0;
background-color: hsl(0 0% 100% / 87%);
}

.gallery figure:hover figcaption {
transform: translateY(0);
}

And ta-da! We have a basic animated caption.

Ken Burns image effect

You may not have known the name, but you've seen the effect: a slow, smooth pan and zoom combo of a still image, so named due to being popularized by documentary filmmaker Ken Burns.

Using the principles we've already covered with the transition and tranform properties, we can again combine them on the img to add this effect on hover as well.

We add an additional value to transform to set the default scale to 0 since on hover we'll be scaling it up so we need to set the point it starts from. We're using a generous duration of 1200ms for the transition to take place in order to create a smooth pan and zoom effect.

.gallery img {
transform: scale(1) translate(0, 0);
transition: transform 1200ms ease-in;
}

Next we add the :hover transition into the figure rule, adding both a bit more of a scale up for the zoom-in effect, in addition to pulling it back left on the x-axis to -8% and also a bit up on the y-axis with -3%. You can adjust the translate values to your taste.

.gallery figure:hover img {
transform: scale(1.3) translate(-8%, -3%);
}

There's one more thing, which is that we have set our transition durations with a 400ms difference. We can add that value as a delay for the caption. Be aware that the delay applies prior to the transition on hover, and at the end of the transition out off-hover. Personally I like this effect since it means that in both directions the animations end together.

.gallery figcaption {
/* update to add the 400ms delay */
transition: transform 800ms 400ms ease-in;
}

Altogether, here is our gallery with the Ken Burns effect on the image and caption.

CSS for "Ken Burns style animated figures"
.gallery img {
transform: scale(1) translate(0, 0);
transition: transform 1200ms ease-in;
}

.gallery figure:hover img {
transform: scale(1.3) translate(-8%, -3%);
}

.gallery figcaption {
/* added 400ms delay */
transition: transform 800ms 400ms ease-in;
}

Don't forget about :focus

Hover is fine for mouse-users, but what about those who for various reasons use primarily their keyboard to navigate?

The li element isn't inherently a focusable element, so just adding :focus styles will not change behavior.

We have two options:

  • If you plan to link the images anyway, wrap the figure with a link element and hook :focus styles to that
  • If a link isn't needed, apply tabindex="0" to each figure which will enable them as focusable elements

We'll use the tabindex approach for this demo.

<figure tabindex="0"></figure>

You can test this by tabbing and you will notice the standard focus halo outline.

We'll customize the outline and also update the rules to apply the same :hover behavior on :focus.

CSS for "Reveal captions on figure:focus"
.gallery figure:focus {
outline: 2px solid white;
outline-offset: 2px;
}

.gallery figure:hover figcaption,
.gallery figure:focus figcaption
{
transform: translateY(0);
}

.gallery figure:hover img,
.gallery figure:focus img
{
transform: scale(1.3) translate(-8%, -3%);
}

Handling for touch devices

We've made a large assumption so far which is that users interacting with our gallery have a hover capable device and the motor abilities required to perform a "hover" on an element.

While the current hover experience somewhat works on a touch device, if you upgrade the gallery to use links it's likely the caption wouldn't have time to show prior to the navigation event. So, let's instead change our strategy to only enable the animated links for hover-capable devices and set the default to display them.

This is done with a media query combo to detect both hover and a "fine" pointing device which is likely to mean the user is primarily using a mouse, possibly a stylus. The keyword here is "likely" as there are devices capable of touch sometimes, and more "fine" pointers other times. For more info to help you make an informed decision, check out this excellent overview of interaction media features from Patrick H. Lauke.

We'll remove the transform on the figcaption and instead only apply it if this media query combo is valid. If you're on a touch device you'll likely see the captions by default in this next demo, or you can emulate a mobile or touch device using your browser dev tools.

CSS for "Only animate captions for non-touch devices"
.gallery figcaption {
transform: translateY(100%);
/* provide stacking context */
z-index: 1;
}

@media (any-hover: hover) and (any-pointer: fine) {
.gallery figcaption {
transform: translateY(100%);
}
}

Respecting user motion preferences

Some users may have a need for a "reduced motion" experience, which we can handle by way of a media query as well.

The prefers-reduced-motion media query will let us remove the transition of the caption and image when the user has updated their system settings to request reduced motion. You can learn more about this preference media query in my overview.

When a reduced motion setting is true, we'll remove the associated transition and transform values. The result will be that the image does not have the Ken Burns effect and the caption appears instantly with no transition.

CSS for "Remove animation for prefers-reduced-motion"
@media (prefers-reduced-motion: reduce) {
.gallery * {
transition-duration: 0ms !important;
}

.gallery img {
transform: none !important;
}

.gallery figcaption {
transition-delay: 0ms;
}
}

Optional: Vignette

Another hallmark of the Ken Burns style is a vignette - the soft black gradient on the borders of the image. We can accomplish this with an inset box-shadow. However, an inset box-shadow will not work on the image element directly, so instead we apply it on an :after pseudo element of the figure:

The vignette is positioned by applying it to the single named grid-area and ensuring it has a height and width to take up the whole card in addition to relative positioning to stack it above the image.

CSS for "Vignette effect"
.gallery figure::after {
content: "";
grid-area: card;
width: 100%;
height: 100%;
box-shadow: inset 0 0 2rem 1rem hsl(0 0% 0% / 65%);
position: relative;
}

Choose the "Open in CodePen" option to generate a new CodePen that includes the final styles created for this component.

Next steps: upgrade from a basic img

In this simple gallery example, we just used a basic img element. If you'd like to learn how to use modern image formats and improve performance of your images, review my guide to image display elements.