Fixed stroke width in SVG

Question

I would like to be able to set the stroke-width on an SVG element to be "pixel-aware", that is always be 1px wide regardless of the current scaling transformations applied. I am aware that this may well be impossible, since the whole point of SVG is to be pixel independent.

Context follows:

I have an SVG element with its viewBox and preserveAspectRatio attributes set. It looks something like this

<svg version="1.1" baseProfile="full"
    viewBox="-100 -100 200 200" preserveAspectRatio="xMidYMid meet"
    xmlns="http://www.w3.org/2000/svg" >
</svg>

This means that when I scale that element, the actual shapes inside it scale accordingly (so far so good).

As you can see, I have set up the viewBox so that the origin is in the center. I would like to draw an x- and a y-axis within that element, which I do thus:

<line x1="-1000" x2="1000" y1="0" y2="0" />

Again, this works fine. Ideally, though, this axis would always be only 1px wide. I have no interest in the axes getting fatter when i scale the parent svg element.

So am I screwed?

Zach Saucier · Accepted Answer · 2016-05-12 18:55:12Z

192

You can use the vector-effect property set to non-scaling-stroke, see the docs. Another way is to use transform(ref).

That will work in browsers that support those parts from SVG Tiny 1.2, for example Opera 10. The fallback includes writing a small script to do the same, basically inverting the CTM and applying it on the elements that shouldn't scale.

If you want sharper lines you can also disable antialiasing (shape-rendering=optimizeSpeed or shape-rendering=crispEdges) and/or play with the positioning.

edited May 12, 2016 at 18:55

Zach Saucier

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answered Aug 20, 2009 at 7:49

Erik Dahlström

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9 Comments

wxs Over a year ago

Unfortunately this is in a XUL app, and that doesn't seem to support vector-effect yet. Oh well.

Robert Longson Over a year ago

This should appear in Firefox 15 all being well so you should be able to use it once you build your XUL app on gecko 15.

merlin Over a year ago

IE11 still doesn't support vector-effect property. Is it possible to achieve the same effect as vector-effect: non-scaling-stroke in IE11?

Erik Dahlström Over a year ago

@merlin yes, with js it's possible to emulate this in IE.

Erik Dahlström Over a year ago

@merlin clone the element (setting fill to none and vice versa for the stroke), compute & set the appropriate transforms (one for the fill part and one for the stroke part). It's going to be a little messy for sure, but there it is - you might also want to ask Microsoft to add support for it. In any case I think your question deserves to be a question of its own.

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supersan · Accepted Answer · 2022-01-03 22:49:45Z

11

Here is a more concise answer based on Erik's answer to help you get started quickly.

<div style="background: blue; width: 100%; height: 130px;">
            <svg xml:id="root" viewBox="0 0 100 100" width="100%" height="100%" preserveAspectRatio="none">
                <rect xml:id="r" vector-effect="non-scaling-stroke" x="0" y="0" width="100" height="100" fill="none" stroke="#88CE02"
                      stroke-linecap="square" stroke-width="10" stroke-miterlimit="30"/>
            </svg>
        </div>

Adding the vector-effect="non-scaling-stroke" to the SVG rect makes the border size (or stroke size) fixed.

answered Jan 3, 2022 at 22:49

supersan

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