svelte-compare-image

A Svelte component to compare two images with a slider to reveal one over the other. Find the package on NPM at svelte-compare-image.

An interactive example can be found at https://projects.brianm.me/svelte-compare-image/

This component is CI tested against Svelte 4, but should work with Svelte 3 as well.

Changes are run inside of requestAnimationFrame to improve performance and reduce lag.

Docs

The component will display the images and fill available width and height the aspect ratios of the first image.

To use it, render the component as seen below, providing image src and alt text for the left and right images. The following CSS custom properties are optional and can be set to customize the appearance of the slider.

Props

Property	Default Value
--handle-size	2.5rem
--handle-background-color	rgba(0, 0, 0, 0.6)
--handle-background-image	see below
--handle-border-width	0.125rem
--slider-color	#ffffff
--slider-width	0.125rem

Default thumb background image:

url('data:image/svg+xml;utf8,<svg viewBox="0 0 24 24" xmlns="http://www.w3.org/2000/svg"><path d="M3 12H21M3 12L7 8M3 12L7 16M21 12L17 16M21 12L17 8" stroke="white" stroke-width="2" stroke-linecap="round" stroke-linejoin="round"/></svg>')

It looks like this (shown with darkgray for viewing here, it is white in the component)

Slots

CompareImage has one named slot, slider-label, which is used to label the slider control. It is displayed in a visually hidden span. The default value is the following:

Set the visibility of one image over the other. 0 is full visibility of the second image and 100 is full visibility of the first image. Any amount in-between is a left/right cutoff at the percentage of the slider.

Example

<script lang="ts">
  import { CompareImage } from "svelte-compare-image";
  // or
  import CompareImage from "svelte-compare-image/CompareImage.svelte";

  // too many quotes to deal with, storing as a variable is easier
  const handleBackgroundImage = `url('data:image/svg+xml;utf8,<svg viewBox="0 0 24 24" xmlns="http://www.w3.org/2000/svg"><path d="M3 12H21M3 12L7 8M3 12L7 16M21 12L17 16M21 12L17 8" stroke="white" stroke-width="2" stroke-linecap="round" stroke-linejoin="round"/></svg>')`;
</script>

<CompareImage
  imageLeftSrc="https://via.placeholder.com/600x400/ffaa00/ffffff/?text=Example+Text"
  imageLeftAlt="left"
  imageRightSrc="https://via.placeholder.com/600x400/00aaff/ffffff?text=Example+Text"
  imageRightAlt="right"
  --handle-size="2.5rem"
  --handle-background-color="rgba(0, 0, 0, 0.6)"
  --handle-background-image={handleBackgroundImage}
  --handle-border-width="0.125rem"
  --slider-color="#ffffff"
  --slider-width="0.125rem"
>
  <svelte:fragment slot="slider-label">
    Set the visibility of one image over the other. 0 is full visibility of the
    second image and 100 is full visibility of the first image. Any amount
    in-between is a left/right cutoff at the percentage of the slider.
  </svelte:fragment>
</CompareImage>