Normally, the <clipPath> element hides everything that is outside the clip path. To achieve the opposite effect - that is to "cut out" something from the image - i want to use two paths in the clipPath and the clip-rule="evenodd" attribute. Basically, I want to "xor" the clip paths.
But it doesn't work. It shows the region "ORed":
<clipPath clip-rule="evenodd" id="imageclippath" clipPathUnits = "objectBoundingBox">
<rect clip-rule="evenodd" x="0.3" y="0.3" height="0.6" width="6" />
<rect clip-rule="evenodd" x="0" y="0" height="0.5" width="0.5" />
</clipPath>
<rect clip-path="url(#imageclippath)" x="0" y="0" height="500" width="500" fill="red"/>
EDIT:
My problem is that AFAIK <mask> doesn't work in iOS WebKit.
It's much easier to do what you're after with a mask, see this example. Here's the mask definition:
<mask id="maskedtext">
<circle cx="50%" cy="50%" r="50" fill="white"/>
<text x="50%" y="55%" text-anchor="middle" font-size="48">ABC</text>
</mask>
Regions that are white inside the mask will be kept, everything else will be clipped away.
Here's another example that uses clipPath instead, is a bit trickier since you need to use a path element to get the clip-rule to apply. The clipPath that uses clip-rule there looks like this:
<clipPath id="clipPath1">
<path id="p1" d="M10 10l100 0 0 100 -100 0ZM50 50l40 0 0 40 -40 0Z" clip-rule="evenodd"/>
</clipPath>