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When you want an image with both a compressed background and a pixel perfect text on top... Merges a JPEG background and a transparent PNG into a single SVG image
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SVG Image Merge

A tool for image optimization freaks.

This tool is related to this article, which is a good introduction to this tool.

Let's say you want to add an image on your website, that contains both:

  • a photography that could be compressed as a JPEG (using a PNG would make a huge file)
  • some text or logo you want to be pixel perfect (JPEG compression would add some artefacts)

This tool creates an single image, containing both the optimized background and the pixel perfect text.

Of course, this could be done easily in HTML by positioning a transparent <img> over another <img>. Use this tool if you can't do that, if it needs to fit in a single field of a back-office for exemple.

Here is an example result file:

svg example

How it works

It's very simple. It takes two images on your computer, base64 encodes both of them, then creates an SVG. The structure of the SVG is very simple and looks basically like this:

<svg width="800" height="600">
    <image x="0" y="0" width="800" height="600" xlink:href="data:image/jpg;base64,{{base64-encoded-background}}" />
    <image x="0" y="0" width="800" height="600" xlink:href="data:image/png;base64,{{base64-encoded-top}}" />

Once it's done, simply serve the new SVG like any other image in your HTML:

<img src="merged-image.svg" />

Don't forget to check that your server is configured to properly gzip SVG images (content type image/svg+xml).


npm install -g svg-image-merge


svg-image-merge <background-file> <top-file> <output-file>


svg-image-merge background.jpg wording.png result.svg


None for the moment

Browser compatibility

Be careful! Safari 8 is not able to display base64 encoded images inside an SVG if the SVG is loaded via <img>. It's working correctly with an <object> tag. It is fixed in Safari 9.

IE8 is not able to understand SVG images at all.


Gaël Métais. I'm a webperf freelance. Follow me on Twitter @gaelmetais, I tweet about Web Performances, Front-end and new versions of YellowLabTools!

I can also help your company about Web Performances, visit my website.

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