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Add lossless transformation conditions

Ralek Kolemios requested to merge rkolemios/krita:ralekarts/lossless-transformation-conditions into master

Something that always bothered me was how lossy some transformations could be, and while simple translations were fixed a while ago when I first reported it, I had recently discovered that mirrors and 90-degree rotations were still lossy. In this MR I hoped to fix that as best I could.

I've added a new 'lossless transform' section which works with integer values during the matrix transforms to ensure that the final result aligns to the pixel grid.

Rotations in increments of 90 degrees, and perfect x and y mirrors should now be lossless. This should greatly help out pixel artists, who I believe previously could not use these functions at all.

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Test Plan

The transform tool and mask should behave as normal in nearly every way except that it shouldn't lose quality in the above circumstances.

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  • I confirmed this builds.
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