110 lines
4 KiB
Markdown
110 lines
4 KiB
Markdown
Mini SVG `data:` URI
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====================
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This tool converts SVGs into the most compact, compressible `data:` URI that SVG-supporting browsers tolerate. The results look like this (169 bytes):
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```url
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data:image/svg+xml,%3csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 50 50'
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%3e%3cpath d='M22 38V51L32 32l19-19v12C44 26 43 10 38 0 52 15 49 39 22 38z'/%3e
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%3c/svg%3e
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```
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Compare to the Base64 version (210 bytes):
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```url
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data:image/svg+xml;base64,PHN2ZyB4bWxucz0iaHR0cDovL3d3dy53My5vcmcvMjAwMC9zdmciIH
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ZpZXdCb3g9IjAgMCA1MCA1MCI+PHBhdGggZD0iTTIyIDM4VjUxTDMyIDMybDE5LTE5djEyQzQ0IDI2ID
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QzIDEwIDM4IDAgNTIgMTUgNDkgMzkgMjIgMzh6Ii8+PC9zdmc+
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```
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Or the URL-encoded version other tools produce (256 bytes):
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```url
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data:image/svg+xml;charset=US-ASCII,%3Csvg%20xmlns%3D%22http%3A%2F%2Fwww.w3.org%
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2F2000%2Fsvg%22%20viewBox%3D%220%200%2050%2050%22%3E%3Cpath%20d%3D%22M22%2038V51
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L32%2032l19-19v12C44%2026%2043%2010%2038%200%2052%2015%2049%2039%2022%2038z%22%2
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F%3E%3C%2Fsvg%3E
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```
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For a more realistic example, I inlined the icons from the [Open Iconic](https://useiconic.com/open) project into CSS files with the 3 above methods:
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| Compression | Base64 | Basic %-encoding | `mini-svg-data-uri` |
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|-------------|----------:|-----------------:|--------------------:|
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| None | 96.459 kB | 103.268 kB | 76.583 kB |
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| `gzip -9` | 17.902 kB | 13.780 kB | 12.974 kB |
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| `brotli -Z` | 15.797 kB | 11.693 kB | 10.976 kB |
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Roughly 6% smaller compressed, but don't write off the ≈20% uncompressed savings either. [Some browser caches decompress before store](https://blogs.msdn.microsoft.com/ieinternals/2014/10/21/compressing-the-web/), and parsing time/memory usage scale linearly with uncompressed filesize.
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Usage
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-----
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```js
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var svgToMiniDataURI = require('mini-svg-data-uri');
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var svg = '<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 50 50"><path d="M22 38V51L32 32l19-19v12C44 26 43 10 38 0 52 15 49 39 22 38z"/></svg>';
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var optimizedSVGDataURI = svgToMiniDataURI(svg);
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// "data:image/svg+xml,%3csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 50 50'%3e%3cpath d='M22 38V51L32 32l19-19v12C44 26 43 10 38 0 52 15 49 39 22 38z'/%3e%3c/svg%3e"
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```
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You can also [try it in your browser at RunKit](https://npm.runkit.com/mini-svg-data-uri).
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### CLI
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If you have it installed globally, or as some kind of dependency inside your project’s directory:
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```sh
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mini-svg-data-uri file.svg # writes to stdout
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mini-svg-data-uri file.svg file.svg.uri # writes to the given output filename
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```
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Use `--help` for more info.
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### Warning
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* This **does not optimize the SVG source file**. You’ll want [svgo](https://github.com/svg/svgo) or its brother [SVGOMG](https://jakearchibald.github.io/svgomg/) for that.
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* The default output **does not work inside `srcset` attributes**. Use the `.toSrcset` method for that:
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```js
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var srcsetExample = html`
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<picture>
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<source srcset="${svgToMiniDataURI.toSrcset(svg)}">
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<img src="${svgToMiniDataURI(svg)}">
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</picture>`;
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```
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* The resulting Data URI should be wrapped with double quotes: `url("…")`, `<img src="…">`, etc.
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* This might change or break SVGs that use `"` in character data, like inside `<text>` or `aria-label` or something. Try curly quotes (`“”`) or `"` instead.
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FAQ
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---
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### Don’t you need a `charset` in the MIME Type?
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`charset` does nothing for Data URIs. The URI can only be the encoding of its parent file — it’s included in it!
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### Why lowercase the URL-encoded hex pairs?
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It compresses slightly better. No, really. Using the same files from earlier:
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| Compression | Uppercase (`%AF`) | Lowercase (`%af`) |
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|-------------|------------------:|------------------:|
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| `gzip -9` | 12.978 kB | 12.974 kB |
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| `brotli -Z` | 10.988 kB | 10.976 kB |
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I did say *slightly*.
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Browser support
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---------------
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* Internet Explorer 9 and up, including Edge
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* Firefox, Safari, Chrome, whatever else uses their engines
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* Android WebKit 3+
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* Opera Mini’s server-side Presto
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