Handbuch:Kodierungskonventionen/SVG

Diese Seite beschreibt die Kodierungskonventionen, die in Dateien der MediaWiki-Codebasis verwendet werden, die in SVG geschrieben wurden. Siehe auch die allgemeinen Konventionen, die für alle Programmiersprachen gelten, einschließlich derer für SVG.

We make use of SVGO as optimisation tool, see automated optimisation below.

Code-Struktur

Minimal code as possible with readability in mind is the premise.

Example for simple optimised file – subtract.svg from OOUI:

<?xml version="1.0" encoding="UTF-8"?>
<svg xmlns="http://www.w3.org/2000/svg" width="20" height="20" viewBox="0 0 20 20">
	<title>
		subtract
	</title>
	<path d="M4 9h12v2H4z"/>
</svg>

For minimalists, exactly the same can be drawn with

<?xml version="1.0"?>
<svg xmlns="http://www.w3.org/2000/svg" width="20" height="20">
    <path d="m4,9h12v2H4"/>
</svg>

Example for slightly more complex, optimised file – BetaFeatures screenshot template:

<?xml version="1.0" encoding="UTF-8"?>
<svg xmlns="http://www.w3.org/2000/svg" width="264" height="162" viewBox="0 0 264 162">
    <title>
        BetaFeatures screenshot template
    </title>
    <defs>
        <clipPath id="jagged-edge">
            <path d="M0 0v152l12 10 12-10 12 10 12-10 12 10 12-10 12 10 12-10 12 10 12-10 12 10 12-10 12 10 12-10 12 10 12-10 12 10 12-10 12 10 12-10 12 10 12-10V0z"/>
        </clipPath>
    </defs>
    <g fill="#eaecf0" clip-path="url(#jagged-edge)">
        <path id="background" fill="#fff" d="M0 0h264v162H0"/>
        <path id="logo" d="M11 22c0-8 6-14 14-14s14 6 14 14-6 14-14 14-14-6-14-14M38 45v-5H13v5h25"/>
        <path id="sidebar" d="M38 163V58H13v106h25"/>
        <path id="personal-tools" d="M233 5h26v6h-26V5zM209 5h22v6h-22zM185 5h22v6h-22zM162 5h13v6h-13zM177 5h6v6h-6zM154 5h6v6h-6z"/>
        <path id="search-input" d="M258 16v4h-92v-4h92m1-1h-94v6h94v-6z"/>
        <path id="search-icon" d="M168 17h2v2h-2z"/>
        <path id="article" d="M252 162V29H48v133z"/>
        <path id="border" d="M0 0v162h264V0zm1 1h262v150.533l-11 9.166-12-10-12 10-12-10-12 10-12-10-12 10-12-10-12 10-12-10-12 10-12-10-12 10-12-10-12 10-12-10-12 10-12-10-12 10-12-10-12 10-11-9z"/>
    </g>
</svg>

We will explain the different coding conventions in the following section.

Automatisierte Optimierung (SVGO)

SVGO was maintained by Kir Belevich (deepsweet) and Lev Solntsev (GreLI) from August 2012 to 2016 and since 2021 by Bogdan Chadkin (TrySound).

How to use

Is it recommended to install svgo from https://github.com/svg/svgo or from npm for the command line. There is also an in-browser demo to help with preview and general understanding of the tool at https://jakearchibald.github.io/svgomg/. This should not be used to create production files however.

Safe plugins:

As some SVGO default plugins (options) might result in unexpected appearance with more complex SVGs, we differentiate between safe, considerably less-safe and unsafe plugins. Set the "transformPrecision" at least to 7 to reduce the rist of breaking files. When using unsafe plugins it's recommended to verify before and after diffing per file to ensure visual quality.

Mentioning only plugins, that are changed from default setting or that might be counter-intuitive:

• Sorting attributes sortAttrs.
  Enable by setting to true; disabled by default
• Remove or cleanup enable-background attribute when possible cleanupEnableBackground.
  Deprecated attribute, only supported by IE/Edge; enabled by default

See SVGO Readme for other enabled, safe plugins.

Plugins to consider carefully: 

cleanupIDs	Remove unused and minify used IDs Might negatively affect readability and breaks some files; enabled by default
removeRasterImages	As general rule dangerous, could cause data loss, some raster-images are difficult to spot; disabled by default
inlineStyles	Some users prefer to use CSS than inlineStyles, can reduce editability
removeDoctype	For SVG 1.1 there is not reason to remove it, however for the upcommong SVG2-draft it will be deapreciated

Unsafe rules to disable (don't use!):

convertPathData	Might cause (i) imprecise rendering, (ii) wrong rendering by librsvg, (iii) breaking files; enabled by default
cleanupListOfValues	Round/rewrite number lists breaks Wikimedia-renderin
convertShapeToPath	can reduce readability and breaks files
removeXMLProcInst	Remove XML processing instructions, aka XML declaration <?xml version="1.0" encoding="UTF-8"?> Issues when viewed as standalone file in some editors, also possible issues with MIME type interpretation Example: If the SVG doesn't start with an XML declaration, then its MIME type will be detected as text/plain rather than image/svg+xml by libmagic and consequently, MediaWiki's CSSMin CSS minifier. libmagic's default database currently requires that SVGs contain an XML declaration; disable by setting to false; enabled by default
removeTitle	Remove ‎<title> Problematic for accessibility reasons; set to false; enabled by default
removeDesc	Remove ‎<desc> Problematic for accessibility reasons; set to false; enabled by default
removeViewBox	Remove viewBox attribute Results in troublesome appearance in some browsers, therefore both, width/height and viewbox should be featured; set to false; enabled by default
removeDimensions	Remove dimensions width/height when viewbox is available As above; set to false; disabled by default
removeMetadata	Possible Copyright-Information
removeHiddenElems	Possible reference lines, editor data, real text before convertion, Copyright-informations
removeUnknownsAndDefaults	removes Flow-Text
cleanupNumericValues	breaks some files
minifyStyles	breaks some files
removeComments	reduces readability and possible removes reference lines, editor data, real text before convertion, Copyright-informations
removeEditorsNSData	reduces editability with GUI-SVG-Editors
collapseGroups	reduced readability and editability and breaks some files
removeStyleElement	breaks some files
removeOffCanvasPaths	breaks some files
removeEmptyContainers	breaks some files
removeElementsByAttr	breaks some files
convertStyleToAttrs	breaks some files
convertTransform	breaks some files
cleanupNumericValues	breaks some files
inlineStyles	breaks some CSS-features
reusePaths	breaks some files

Exemplified safe configuration

Note that this is for SVGO v1.x; v2.x takes different CLI arguments:

$ svgo path/to/image.svg --disable={cleanupIDs,convertPathData,removeDesc,removeTitle,removeViewBox,removeXMLProcInst} --enable='sortAttrs' --pretty --final-newline

Use pretty output for human readable code and in the process indent code by tabs.

Exemplified safe configuration (.svgo.config.js)

Juni 2023 - SVGO v3.0.0+ compatibility, amending to new cleanupIds plugin name. (phab:T324899)

Januar 2022 - NPM run scripts enabled SVGO configuration. (phab:T246321)

/**
 * SVGO Configuration
 * Compatible to v3.0.0+
 * Recommended options from:
 * https://www.mediawiki.org/wiki/Manual:Coding_conventions/SVG#Exemplified_safe_configuration
 */

'use strict';

module.exports = {
	plugins: [
		{
			// Set of built-in plugins enabled by default.
			name: 'preset-default',
			params: {
				overrides: {
					cleanupIds: false,
					removeDesc: false,
					removeTitle: false,
					removeViewBox: false,
					// If the SVG doesn't start with an XML declaration, then its MIME type will be detected as "text/plain" rather than "image/svg+xml" by libmagic and, consequently, MediaWiki's CSSMin CSS minifier.
					// libmagic's default database currently requires that SVGs contain an XML declaration:
					// https://github.com/threatstack/libmagic/blob/master/magic/Magdir/sgml#L5
					removeXMLProcInst: false // https://phabricator.wikimedia.org/T327446
					convertPathData: false // https://github.com/svg/svgo/issues/880 https://github.com/svg/svgo/issues/1487
					removeMetadata: false // Copyright-Violation
					removeHiddenElems: false // source for converted text2path
					removeUnknownsAndDefaults: false // removes Flow-Text: https://commons.wikimedia.org/wiki/User:JoKalliauer/RepairFlowRoot
					cleanupNumericValues: false // https://github.com/svg/svgo/issues/1080
					minifyStyles: false //https://github.com/svg/svgo/issues/888
					removeComments: false //reduces readability
					removeEditorsNSData: false // https://github.com/svg/svgo/issues/1096
					collapseGroups: false // https://github.com/svg/svgo/issues/1057
					removeOffCanvasPaths: false //https://github.com/svg/svgo/issues/1732
					removeEmptyContainers: false // https://github.com/svg/svgo/issues/1194 https://github.com/svg/svgo/issues/1618
					convertTransform: fasle // https://github.com/svg/svgo/issues/988 https://github.com/svg/svgo/issues/1021
					cleanupNumericValues: false // https://github.com/svg/svgo/issues/1080
					inlineStyles: false // https://github.com/svg/svgo/issues/1486
				}
			}
		},
		'removeRasterImages',
		'sortAttrs'
	],
	// Set whitespace according to Wikimedia Coding Conventions.
	// @see https://github.com/svg/svgo/blob/main/lib/stringifier.js#L39 for available options.
	js2svg: {
		eol: 'lf',
		finalNewline: true,
		// Configure the indent to tabs (default 4 spaces) used by '--pretty' here.
		indent: "\t",
		pretty: true
	},
	multipass: true
}

Exemplified safe configuration (Gruntfile.js)

svgmin: {
	options: {
		js2svg: {
			indent: '\t',
			pretty: true
		},
		plugins: [ {
			cleanupIDs: false
		}, {
			removeDesc: false
		}, {
			removeRasterImages: true
		}, {
			removeTitle: false
		}, {
			removeViewBox: false
		}, {
			removeXMLProcInst: false
		}, {
			sortAttrs: true
		}, {
			convertPathData: false // https://github.com/svg/svgo/issues/880
		}, {
			removeMetadata: false // Copyright-Violation
		}, {
			removeHiddenElems: false // source for converted text2path
		}, {
			removeUnknownsAndDefaults: false // removes Flow-Text
		}, {
			cleanupNumericValues: false // https://github.com/svg/svgo/issues/1080
		}, {
			minifyStyles: false //https://github.com/svg/svgo/issues/888
		}, {
			removeComments: false //reduces readability
		}, {
			removeEditorsNSData: false // https://github.com/svg/svgo/issues/1096
		}, {
			collapseGroups: false // https://github.com/svg/svgo/issues/1057
		}, {
			removeOffCanvasPaths: false //https://github.com/svg/svgo/issues/1732
		}, {
			removeEmptyContainers:false // https://github.com/svg/svgo/issues/1194 https://github.com/svg/svgo/issues/1618
		}, {
			convertTransform: fasle // https://github.com/svg/svgo/issues/988 https://github.com/svg/svgo/issues/1021
		}, {
			cleanupNumericValues: false // https://github.com/svg/svgo/issues/1080
		}, {
			inlineStyles: false // https://github.com/svg/svgo/issues/1486
		} ]
	}
}

Manuelle Optimierung

Beyond automated optimising SVGs there are further steps to consider:

• retain the following code xml:space="preserve", <!--, <title, \n, \r, \t, <g, visibility="hidden", opacity="0", display="none", requiredFeatures=", <?xml version="1.0" encoding="UTF-8"?>, ‎<defs>, <rect, <style type="text/css", class=", data-name=, inkscape:label, <rdf:RDF, aria-label=, <inkscape:grid, <sodipodi:guide, sodipodi:cx=, sodipodi:cy=, sodipodi:rx=, sodipodi:ry=, sodipodi:type="arc", vector-effect=, inkscape:groupmode="layer", inkscape:label=, sodipodi:role="line", see c:Help:SVG guideline
• Remove standalone="no" from XML processing instruction, as it's default
• Lowercase (for better gzipping) and shorten hex color values, if possible, e.g. #fff instead of #FFFFFF.
• Attributes that are the same for a group of elements can be applied to a common parent ‎<g> instead, or sometimes even specified by the <svg statement (see an example: CHE Bettens COA.svg).
  This might reduce the editability or readability
• Rely on defaults like fill="#000" and stroke-width="1".
• The <path d="…"/> syntax is almost always shorter than the syntax of basic shapes like ‎<polygon> or even ‎<rect>, however ‎<circle>, ‎<ellipse>, ‎<rect> are generally more easy to read/edit, therfore there is generally prefered to use more specific ones.
• Merge <path d="…"/> elements where applicable. Do not do that if the both path should be edited speratly.
• Do not remove redundant ry="…" attribute when identical to rx="…" it get's more difficult to read/edit.
• Remove not needed fill-rule="…" and clip-rule="…". These rules only have an effect on certain paths, e.g. when a path intersects itself.
• Look for IEEE rounding errors like 0.999999998 or 1.000000003. Such numbers take up space without providing any additional information. They can almost always be cut off without visually changing anything.
• Work with a non-fractional pixel grid while drawing, and align as much points as possible on this grid. These points have a much higher chance of being represented as short integer numbers in the resulting code.
• Pick a non-fractional grid so that it matches the features of an existing image, and scale or redraw shapes so that as many points as possible fall on the grid. The result might be misaligned and can be cropped using viewBox="<left> <top> <width> <height>".

If you want to dig even deeper, there are more optimisations to compress delivery, such as:

• auto-closing paths (aka removing z for certain shapes),
• use relative commands when creating paths (instead of absolute commands, e.g. "m" for "move by", instead of "M" for "move to"),
• optimising for compression backreferences

Other tools

Other tools that may be helpful to know about:

1. SvgWorkAroundBot
2. SVGOMG
3. scour
4. svgcleaner
5. check Help:SVG guidelines#How to optimize for more options.

scour

Description and history

This optimizer was one of the first optimizers: Since 2009 it included with the installation of Inkscape, it can be used by saving Inkscape-files with "Optimized Inkscape SVG", and in 2013 seperated into an self-contained project available at https://github.com/scour-project/scour. It is maintained by the Inscape-Developer Patrick Storz (Ede123).

How to use

You can use in the browser at https://svgworkaroundbot.toolforge.org/ or install it via pip install scour from the command line (Linux-PC/Mac-PC/Windows).

safe plugins

Scour is a very cautious optimizer, however some plugins can still be break the file or remove important non-visible parts, to be on the safe side you can use scour -i input.svg -o output.svg --disable-simplify-colors --disable-style-to-xml --disable-group-collapsing --keep-editor-data --keep-unreferenced-defs --protect-ids-noninkscape --disable-embed-rasters --set-precision=8 --set-c-precision=8

svgcleaner

Description and history

This optimizer was developed from Jan 2012 to 2022 by Yevhenii Reizner.

It focusses on following the current w3c-Standards (SVG1.1). Compared to scour or svgo it breaks less files, reduces the file size more and the performance is magnitues faster.

How to use

You can use in the browser at https://svgworkaroundbot.toolforge.org/ or download it from https://github.com/RazrFalcon/svgcleaner-gui/releases .

safe plugins

Files will be treated according to the standards, however sometimes file non-svg-elements which are important for reading and/or editing the file, to be on the safe side you can use svgcleaner input.svg output.svg --allow-bigger-file --indent yes --resolve-use no --apply-transform-to-gradients yes --apply-transform-to-shapes yes --convert-shapes no --group-by-style no --join-arcto-flags no --join-style-attributes no --merge-gradients yes --regroup-gradient-stops yes --remove-comments no --remove-declarations no --remove-default-attributes yes --remove-desc no --remove-dupl-cmd-in-paths yes --remove-dupl-fegaussianblur yes --remove-dupl-lineargradient yes --remove-dupl-radialgradient yes --remove-gradient-attributes yes --remove-invalid-stops yes --remove-invisible-elements no --remove-metadata no --remove-needless-attributes yes --remove-nonsvg-attributes no --remove-nonsvg-elements no --remove-text-attributes no --remove-title no --remove-unreferenced-ids no --remove-unresolved-classes yes --remove-unused-coordinates yes --remove-unused-defs yes --remove-version yes --remove-xmlns-xlink-attribute yes --simplify-transforms yes --trim-colors yes --trim-ids no --trim-paths yes --ungroup-defs yes --ungroup-groups no --use-implicit-cmds yes --list-separator comma --paths-to-relative yes --remove-unused-segments yes --convert-segments yes --apply-transform-to-paths yes --coordinates-precision 2 --paths-coordinates-precision 5 --properties-precision 3 --transforms-precision 7

References