This filter combines a color matrix and its inverse, so why doesn't this give back the original image? [It converts to YIQ and back to RGB]. Instead it gives back a greyscale image with some reddish artifacts.). This is the same on firefox, safari and IE10, so I think it's my fault, and not a bug.
<filter id="matrixtest" filterUnits="userSpaceOnUse" x="-10" y="-10" width="340" height="220">
<feColorMatrix in="SourceGraphic" result="YIQ" values="0.299 0.587 0.114 0 0 0.596 -0.274 -0.321 0 0 0.211 -0.523 0.311 0 0 0 0 0 1 0"/>
<feColorMatrix in="YIQ" result="RGB" type="matrix" values="1 0.956 0.621 0 0 1 -0.272 -0.647 0 0 1 -1.107 1.705 0 0 0 0 0 1 0"/>
</filter>
Ok I forgot my linear algebra - because matrix multiplication is not commutative, and therefore the inverse is being calculated in the wrong order (needs to be A-1.V, not V.A-1)