collapseGroups causes clip-path on images to be incorrect

[flexpaper]

Firstly, I just wanted to congratulate you on a great project! I have done some initial testing and it looks like you've done some great progress already!

I have found a bug related to clip-path and how collapseGroups is working.
Original:
<clipPath id="clip2">
<path d="M 0 0 L 0 670.671875 L 759.160156 832.039062 L 765.355469 802.894531 L 765.355469 0 Z "/>
</clipPath>
<image id="image5" width="1305" height="1411" xlink:href="data:image/ ...." />

<g clip-path="url(#clip2)" clip-rule="nonzero">
<use xlink:href="#image5" transform="matrix(0.703976,0.149635,-0.149676,0.70417,51.664047,-356.818891)"/>
</g>

Result with collapseGroups active:
<clipPath id="b"><path d="M0 0v670.672l759.16 161.367 6.195-29.145v-802.895z"/></clipPath><image id="c" width="1305" height="1411" xlink:href="data:image/...: />

This causes images to be incorrectly clipped as in the screenshot attached

[flexpaper]

grab the original SVG from here:

https://dl.dropbox.com/u/13295266/Monash_Magazine_1.svg

[deepsweet]

ok, i got it :)
thank you, I'll try to fix it in the minor version next week.

[deepsweet]

the problem is a bit ambiguous because clip-path property is not inheritable, so in our case <g clip-path="..."><use .../></g> doesn't make any sense.

i think that i should to correct removeUnknownsAndDefaults plugin to strip out such cases before collapseGroups will try to move the group's attributes to the content element.

[flexpaper]

sounds like a good idea

[flexpaper]

By the way; this SVG was created using pdftocairo (poppler utility)

[andymerskin]

I am still having issues with this happening on a very simple file with a clipped image. Not exactly sure what is happening here, but after using SVGO, the image no longer appears (probably because the clip-path isn't clipping at the right coordinates or something.

With collapseGroups enabled, the clip-path is added directly to the <image> element. Simply wrapping the <image> with a Group and adding the clip-path back to the group makes it appear correctly without modifying the clip-path definition.

Example SVGs
Original
Optimized
Optimized (collapseGroups disabled) <-- appears correctly

Does this have something to do with relative clip-path positioning?