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Randarar randarars SVGs with placeholders to PNG

Create social media sharable images with dynamic content by using a single url

Explanation

Why

If you share websites, a lot of tools like slack, linkedin and twitter show a preview image of the webpage. Randarar allows you to add dynamic content to your images with a very simple solution.

How

You tell Randarar which image you want to render and the placeholders (your dynamic content) and you get back a ready made image.

The url looks like this:

https://p.salmo.link/render.png?s=https://raw.githubusercontent.com/p0wl/randarar/main/example/svg/onruby_share.svg&title=Remote%20Ruby%20Usergroup%20Hamburg&month=December%202020&participants=6

Image with 14 participants

You can change the parameters (e.g. increase the number of participants) and get an updated image:

https://p.salmo.link/render.png?s=https://raw.githubusercontent.com/p0wl/randarar/main/example/svg/onruby_share.svg&title=Remote%20Ruby%20Usergroup%20Hamburg&month=December%202020&participants=7

Image with 14 participants

Full Example

Url: https://p.salmo.link/render.png?s=https://raw.githubusercontent.com/p0wl/randarar/main/example/svg/onruby_share.svg&title=Remote%20Ruby%20Usergroup%20Hamburg&month=December%202020&participants=6%20Participants&host=Host:%20Irina%20Lindt,%2009.12.2020%20um%2019:00&location=Online%20via%20Zoom&logo=https://hamburg.onruby.de/assets/labels/hamburg-b38fc9aa8aea505fcfe49a9032684ec70dbaab11071a4e9aeea2bf55695cdd3f.png

Generated Image: Result

What you need

You have to prepare an svg image with placeholders. Placeholders are replaced using mustache.js, so you change the dynamic parts of your svg from

<text fill="black" xml:space="preserve" style="white-space: pre" font-family="DM Sans" font-size="20" font-weight="bold" letter-spacing="-0.02em">
  <tspan x="1146.97" y="580.884">99</tspan>
</text>

to

<text fill="black" xml:space="preserve" style="white-space: pre" font-family="DM Sans" font-size="20" font-weight="bold" letter-spacing="-0.02em">
  <tspan x="1146.97" y="580.884">{{participants}}</tspan>
</text>

After that, Randarar can render a dynamic value for the {{ participants }} field

Integration

The Randarar urls are supposed to be integrated via an og:image meta tag. The svg image has to be reachable using https.

You can construct the url to render like this:

https://p.salmo.link/render.png?s=<https://your-svg-url>&<your-placeholder>=<your-value>

# Example:
https://p.salmo.link/render.png?s=https://svgshare.com/i/W0C.svg&title=Hello%20There!

Randarar will return a "Cache-Control": "public, max-age=86400", header, which tells browsers to cache the image. As of now there is no server-side caching enabled.

Replacement Values

Randarar can replace text and also images! For a dynamic image, you replace the inlined image in an svg with a placeholder:

# Original svg:
<image id="image0" width="104" height="104" xlink:href="data:image/png;base64,iVBORw0KG..."/>

# Adjusted, ready for Randarar:
<image id="image0" width="104" height="104" xlink:href="{{ logo }}"/>

and then supply the logo image url:

https://p.salmo.link/render.png?s=https://svgshare.com/i/W0C.svg&logo=https://hamburg.onruby.de/assets/labels/hamburg-b38fc9aa8aea505fcfe49a9032684ec70dbaab11071a4e9aeea2bf55695cdd3f.png

Works with pngs.

Development

Randarar uses sharp to render svg as png images really fast.

Randarar is developed and deployed using aws-cdk.