A package for easily rendering .png images from svelte components in SvelteKit. Inspired by Vercel's
OG Image Generation tool.
Good for rendering dynamic Open Graph images quickly and effeciently without having to use canvas.
- Demo
- Minimal Deployment Demo on Vercel - A quick reference if you need it.
- My blog post detailing how to use this library to create dynamic open-graph images for a sveltekit site
- Renders a normal svelte component as a png
- Component props are supported for dynamic image generation
- Use basic CSS like flexbox and absolute positioning (See valid CSS)
- Lightweight and fast (doesn't use canvas or puppeteer)
- Load custom fonts: tff, otf, woff accepted (woff2 not accepted currently)
The svelte 5 version will be available as the 1.0.0+ release.
You will need to add <svelte:options css="injected" /> to every component you want to render as an image. You will see an error if you don't and the component will not render.
There is currently a bug with the Svelte 5 version deep in a dependency that will render radial gradients fine in dev but will crash production. I am working on a fix.
The Svelte 4 version is available as the 0.1.0 release.
npm install svelte-component-to-image
# Also install @resvg/resvg-js as it contains native bindings that cannot be bundled with the library
npm install @resvg/resvg-jsWhen deploying to serverless platforms, add these configurations to handle the native @resvg/resvg-js module:
vite.config.js:
export default defineConfig({
plugins: [sveltekit()],
build: {
rollupOptions: {
external: ['@resvg/resvg-js']
}
}
});svelte.config.js:
export default {
kit: {
adapter: adapter({
external: ['@resvg/resvg-js']
})
}
};If you're using @sveltejs/adapter-node for traditional server deployment, the package works without additional configuration since Node.js can load native modules directly from node_modules.
- Vercel (working - requires serverless configuration)
- Netlify (working - requires serverless configuration)
- Node.js servers (working - no additional configuration needed)
- Cloudflare Pages (not working - does not support native modules)
This package is NOT for rendering normal svelte components as images, you will need to write your components with image rendering in mind. The guidelines are set by (Satori's CSS Guidelines) - you will need to write your markup and css with these factors in mind.
Create a .svelte component with JS/HTML/CSS. You can pass props or use additional technologies
that require preproccesors like TypeScript or SASS.
<svelte:options css="injected" />
<script lang="ts">
export let text: string = 'hello';
</script>
<div id="container">
<h1>
{text} world!
</h1>
</div>
<style>
* {
display: flex; /* if you're having problems with satori errors, this line can really help */
}
#container {
width: 1200px;
height: 600px;
display: flex;
align-items: center;
justify-content: center;
position: relative;
background: rgb(63, 94, 251);
background: radial-gradient(circle, rgba(63, 94, 251, 1) 0%, rgba(252, 70, 107, 1) 100%);
}
h1 {
color: red;
font-size: 75px;
}
</style>Create a +server.ts endpoint to render and serve the image. Import the package and options type.
More on how the font importing works below.
import { error } from '@sveltejs/kit'
import { dev } from '$app/environment';
import type { RequestHandler } from './$types'
// Svelte Component To Image
import { image_from_component, type RenderOptions } from 'svelte-component-to-image'
// Normal .svelte component
import HelloWorld from './HelloWorld.svelte'
export const GET: RequestHandler = (async ({url}) => {
try {
const options: RenderOptions = {
width: 1200,
height: 600,
props: {
text: url.searchParams.get('text') ?? 'text not found'
},
fonts: [
{
name: 'Typewriter',
url: `${url.origin}/TYPEWR__.TTF`,
weight: 400,
style: 'normal'
}
],
debug: false // you can omit this or set it to true to see logs of data, it can help for debug edge cases
}
// pass the component and options to the package
const image = await image_from_component(HelloWorld, options)
const response = new Response(image)
if(!dev){
// caching on dev will make it hard to see iterations
response.headers.append('Content-Type', 'image/png')
response.headers.append('Cache-Control', 's-maxage=604800, stale-while-revalidate=604800')
}
return response
} catch (e) {
console.error(e)
throw error(500, 'Error trying to generate image from component.')
}
}) satisfies RequestHandlerYou can import as many ttf, otf, and woff fonts as you want to use inside of your component. Although, importing 100 fonts is going to affect server load and speed.
woff2 files are not currently supported.
Fonts files can be local or remote. They need a full URL to be properly loaded. Local fonts
stored in /static can be loaded using ${url.origin}/ as long as {url} is made available
in the endpoint.
Once the font is loaded, you can reference them in the CSS using font-family. If only one font is loaded,
it will be the default.
Not all fonts work! If a font fails to load it will break the image rendering. I am not sure what causes this or which fonts are "approved" - but I have had luck using Font Squirrel's Webfont Generator to convert fonts to web-safe formats and using those.
If you're trying to use a variable weight font like Jost, you will need to use Font Squirrel to generate a separate file per weight and style. It's a pain, I know.
Images can be used and rendered like normal. You will want to set the height and width.
<img src="https://picsum.photos/200/300" width="200" height="300" />This uses Vercel's Satori. You can find out more about what is and isn't supported by reading it's docs: Vercel's Satori
MIT