如何在ems中缩放SVG多边形？ [英] How do I scale an SVG polygon in ems?

问题描述

我直接在HTML5文档中嵌入< svg> 元素，并且想要根据页面的字体大小来缩放重复的背景图案。没问题，SVG支持CSS单元，所以我可以用ems指定大小，对吗？

SVG spec 声明All coordinates 和长度可以使用或不使用单位标识符来指定SVG。而且，实际上，这两种做法正是我所希望的：

 < rect x ='1em'y =' 2em'width ='3em'height ='4em'/> 
< circle cx ='6em'cy ='7em'r ='8em'/> 
  

但是多边形（例如）有自己的完全不同的定义的单词坐标，这样会产生一个错误，而不是画一个三角形：

 < polygon points ='0 0，0 1em，1em 0'/> 
  

路径也是一样 - 可以理解，因为它们已经在使用这些字母来达到不同的目的。

并且转换（如缩放）需要数字，而不是一个坐标或长度，所以这也是不允许的（我的浏览器似乎默默地忽略了transform属性）：

 < polygon points ='0 0，0 1，1 0'transform ='scale（1em）'/> 
  

所以我想我甚至无法弄清楚如何画出1个三角形，更不用说了更复杂。我忽略了一个合理的做法吗？那不合理的方式呢？我应该放弃并使用< canvas> 元素，还是会更糟？

解决方案

您可以将多边形封装在内部< svg> 元素中，以便按需要缩放它们。 viewBox控制它所包含对象的坐标系，height和width属性控制它看起来有多大。

 < svg的xmlns = http://www.w3.org/2000/svg > 
< svg viewBox =0 0 1 1height =1emwidth =1emy =7em> 
< polygon points ='0 0，0 1，1 0'/> 
< / svg> 
< circle cx ='6em'cy ='7em'r ='2em'/> 
< / svg> 
  

I'm embedding an <svg> element directly in an HTML5 document, and I want to scale a repeating background pattern in terms of the page's font size. No problem, SVG supports CSS units, so I can just specify the size in ems, right?

The SVG spec claims "All coordinates and lengths in SVG can be specified with or without a unit identifier." And, indeed, both of these do exactly what I was hoping for:

<rect x='1em' y='2em' width='3em' height='4em' />
<circle cx='6em' cy='7em' r='8em' />

But polygons (for example) have their own completely different definition of the word "coordinate," such that this raises an error instead of drawing a 1 em triangle:

<polygon points='0 0, 0 1em, 1em 0' />

Paths are the same way -- understandably, since they're already using the letters for a different purpose.

And transformations such as "scale" expect a "number," not a "coordinate" or "length", so this isn't allowed either (my browser seems to silently ignore the "transform" attribute):

<polygon points='0 0, 0 1, 1 0' transform='scale(1em)' />

So I guess I can't even figure out how to draw a 1 em triangle, much less anything more complicated. Am I overlooking a reasonable way of doing it? What about an unreasonable way? Should I give up and use a <canvas> element instead, or would that be even worse?

解决方案

You can wrap your polygons in an inner <svg> element to scale them as you wish. The viewBox controls the coordinate system of the objects it contains and the height and width attributes control how big it looks.

<svg xmlns="http://www.w3.org/2000/svg">
  <svg viewBox="0 0 1 1" height="1em" width="1em" y="7em">
      <polygon points='0 0, 0 1, 1 0' />
  </svg>
  <circle cx='6em' cy='7em' r='2em' />
</svg>

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