The XML can store references to the binary chunks in standard formats though, alongside the vector shapes and filters.

  <svg viewBox="## ## ## ##">
    <image xlink:href="layer1.png" x="##" y="##" width="##" height="##"/>
    <image xlink:href="layer2.jpg" x="##" y="##" width="##" height="##"/>
    <rect x="##" y="##" width="##" height="##" fill="red"/>
  </svg>

All that's left is to standardize a way to package it.

Thats actually a good, along with the fake .zip extension.

And why are we storing binary data? The whole point of SVG is everything is in XML unless I'm very mistaken

The author is looking for a container format capable of storing multiple image layers, and one that is capable of storing both vector and raster images.

So you could possibly argue that XML (a la SVG) is the right format to represent the vector files within that container, but it wouldn't be appropriate for the container file itself since binary data really bloats XML.

How else would you propose to store a bitmap.

<points> <point x='2px' y='3px' color='rgba(255,255,255,0)' /> <point x='2px' y='4px' color='rgba(100,255,255,0)' />

    <!--...-->

</points>

heh