Opacity not applied on images

[gdetrez]

Hil Thanks for a nice and useful tool/library!

I'm not sure I'm doing it correctly but I can't apply transparency to included images.
I'm trying to do it by applying style="opacity: 0.5" to the <image/> element. This seems to produce the expected resust with inkscape but not cairosvg. I made an example graphic to demonstrate what is happening: (image is from ttps://www.w3.org/Icons/SVG/svg-logo-v.png)

<?xml version="1.0" encoding="utf-8" ?>
<svg
    width="100" height="200"
    xmlns="http://www.w3.org/2000/svg"
    xmlns:xlink="http://www.w3.org/1999/xlink" >
  <rect fill="red" x="40" y="0" width="20" height="200" />
  <image
      xlink:href="svg-logo-v.png"
      x="15" y="15" width="71" height="71"
      style="opacity: 0.5" />
  <rect
      fill="green"
      x="15" y="115" width="71" height="71"
      style="opacity: 0.5" />
</svg>

Here's the result I get by converting with inkscape (0.92.4, inkscape -e inkscape.png test.svg, left) and cairosvg (2.3.0, cairosvg -o cairosvg.png $PWD/test.svg, right):

It seems that both honor the opacity style of the <rect/> element but cairosvg doesn't honor it on the <image/>.