It would be very useful to be able to sort lines by a range of colours and/or brightness into layers. My end goal would then be to use the sorted layers to apply different hatching to the shapes so that the overlaid shapes create nice shading effects. At the moment it I have not been able to find a way of selecting lines or objects with similar colour / brightness thresholds so that the number of layers generated could be controlled to match the number of pens or effects desired In my case the shapes are separate closed polygons, but are layered on top of each other to achieve a final colour / shade

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block_test.zip