Extract and use height and width of SVG images

[bowman2001]

1. Extract the values. There are two general ways to parse the SVG content as far as I can see:

   1. Use string functions with matching capabilities (findRE or maybe others) to isolate the width and height attributes or the viewBox.
   2. Use transform.Unmarshal to get the full data structure of the SVG.

2. We need to collect and maybe calculate the values (viewBox) for the width and height.

3. Add them to the image tag.

[richtong]

If you need help on this, I wrote stuff that does this. Happy to help, but do not know if this is stale, here is the fragment in https://richtong/hugo-universal-theme

  {{ $svg := readFile $image_local | transform.Unmarshal }}
  <meta property="og:image:width" content="{{ index $svg "-width" }}">
  <meta property="og:image:height" content="{{ index $svg "-height" }}">

This adds it to the Facebook OpenGraph header, but the main ideas are to use readFile and then unmarshal to get the SVG's XML into a Go Map and the use the hugo index. function to find it. Other trick is that parameters and a dash - in them.