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Tutorial: Medium-style image zoom

Medium have an beautiful zoom effect on their images. When clicked, they pop out of the page as a white background fades in behind them. Then, if clicked again, or if a user scrolls away, they pop back into place.

Take a look:

In this tutorial, we’ll learn how to achieve this same effect using Pose for Vue.

Setup

To get started, fork this CodeSandbox template.

App.vue contains a mock article that contains a couple of images. These are being rendered via the component we’re going to work on, ZoomImage.

Open components/ZoomImage.vue, and let’s get started!

State

First, we need to create some state to keep track of whether the image is zoomed or not.

In the component exported from the script section, add a data property that returns our initial state:

export default {
  props: ['imageWidth', 'imageHeight', 'src'],
  data: () => ({ isZoomed: false })
}

Of course, this state is useless on its own. We’re going to need a couple of functions to set the zoom status. After the data prop, add a methods prop with zoomIn and zoomOut functions:

methods: {
  zoomIn() {
    this.isZoomed = true;
  },
  zoomOut() {
    this.isZoomed = false;
  }
}

Finally, we want to toggle the zoomed state when someone clicks the image or, when zoomed in, its white background.

Add a computed property to the component with a toggleZoom property. This will return either zoomIn or zoomOut depending on whether isZoomed is true or false:

computed: {
  toggleZoom() {
    return this.isZoomed ? this.zoomOut : this.zoomIn;
  }
}

In the template section, we can now provide this toggleZoom property to the div:

<div
  v-bind:style="{ width: imageWidth + 'px', height: imageHeight + 'px' }"
  v-on:click="toggleZoom"
>

Now, when the image is clicked, the component will change zoom status. But we’re not responding to this in our template. Let’s make some animations!

Image zoom animation

When the image zooms in, it needs to animate from its place in the document, smoothly into the center of the screen. To do this, we’re going to use Pose’s FLIP capabilities.

You can read the gritty details about FLIP in this blog post by Paul Lewis. In essence, it’s a way of performantly animating between two states that would otherwise be expensive, for instance where position, top, width, or other layout-changing properties have changed.

In Pose, you simply have to add flip: true to a pose, and it’ll automatically perform the usually complicated steps to perform this animation.

Import Pose for Vue:

import posed from 'vue-pose';

Now add a components prop to our exported component, and give it a posed img component named ZoomImage:

components: {
  ZoomImage: posed.img()
}

We’re going to provide the component two poses, one for each zoom state: zoomedIn and zoomedOut.

Our zoomedIn pose is going to set position: fixed and every positional prop to 0. This will pop the content out of the layout and lock it to the viewport.

In our style section, img has a style of margin: auto which centers the image when it’s being stretched across the screen in this way.

ZoomImage: posed.img({
  zoomedIn: {
    position: 'fixed',
    top: 0,
    left: 0,
    bottom: 0,
    right: 0,
    flip: true
  }
})

zoomedOut sets position: static to pop it back into the DOM, as well as setting width and height to auto to make it fill its layout container:

ZoomImage: posed.img({
  zoomedOut: {
    position: 'static',
    width: 'auto',
    height: 'auto',
    flip: true
  },
  zoomedIn: {
    position: 'fixed',
    top: 0,
    left: 0,
    right: 0,
    bottom: 0,
    flip: true
  }
})

We’ve now got our posed img component fully configured. Replace the img component in the render function with it:

<ZoomImage :src="src" />

To animate ZoomImage between the two poses, we need to provide it a pose property.

Add a new computed property, pose. This will return the name of one of our defined poses, 'zoomedIn' or 'zoomedOut', depending on whether isZoomed is true or false:

pose() {
  return this.isZoomed ? 'zoomedIn' : 'zoomedOut';
}

We can now use this pose prop in our template:

<ZoomImage :pose="pose" :src="src" />

Now, when we click our image, it zooms in and out!

I find the automatically generated animation a little bouncy for this purpose. We can define a new transition with a ease curve generated at Lea Verou’s cubic bezier generator.

const transition = {
  duration: 400,
  ease: [0.08, 0.69, 0.2, 0.99]
};

Provide this as a transition prop to both ZoomImage poses, and the animation becomes a little slicker.

Background animation

That’s the (usually) difficult bit out of the way. It’s looking pretty good but the Medium example fades a background in behind the image as it zooms in and out.

Make a new posed component in components called Frame:

Frame: posed.div();

In our style section, add a new rule for .frame. We’re going to make the background of this frame white, and set translateZ(0) to ensure its fade animation is hardware-accelerated:

.frame {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  display: none;
  background: white;
  transform: translateZ(0);
}

And now add Frame as a sibling of Image, also passing it the pose prop:

<Frame :pose="pose" class="frame" />
<ZoomImage :pose="pose" :src="src" />

Now we can animate it! We just want to fade the overlay in and out, so first add those poses:

Frame: posed.div({
  zoomedIn: { opacity: 1 },
  zoomedOut: { opacity: 0 }
});

By itself this won’t do anything, as we’ve got display set to none in the CSS.

For this we can use the applyAtStart and applyAtEnd props. They allow you to define styles to set at the start and at the end of the pose transition, respectively.

Frame: posed.div({
  zoomedIn: {
    applyAtStart: { display: 'block' },
    opacity: 1
  },
  zoomedOut: {
    applyAtEnd: { display: 'none' },
    opacity: 0
  }
});

Now your background will fade in and out behind the image as it zooms in!

Scroll to zoom out

The original Medium image zoom has a nice feature where if a user starts scrolling, the image zooms out back into its original place.

We can accomplish the same thing by adding a 'scroll' event listener to zoomIn, and remove that event listener on zoomOut:

zoomIn() {
  window.addEventListener('scroll', this.zoomOut);
  this.isZoomed = true;
},
zoomOut() {
  window.removeEventListener('scroll', this.zoomOut);
  this.isZoomed = false;
}

Conclusion

Here’s our finished example:

There’s plenty of fun things you can do to improve accessibility and aesthetics.

Have a think about:

  • Closing the image via the esc key
  • Changing the background animation. You could even incorporate SVGs.
  • Adding a “scroll delay” where a user has to scroll a minimum distance before we close the image.
  • Changing the cursor to show a zoom in or zoom out icon.