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In Inkscape, I wish to draw several arcs that are perfectly centred upon each other. The individual arcs need to have different start and end angles. The problem is that when an arc spans less than 360 degrees, the bounding box encompasses only the amount of space taken up by the arc, as opposed to how much space taken if it were a complete 360 degree circle. Therefore, if I should happen to have a bunch of arcs spread over my workspace with different start and end angles, it does not seem possible to centre-align them using the Align and Distribute tools. Similarly, specifying the same X and Y co-ordinates for them simultaneously won't centre them together either.

Can anyone suggest a way around this please? Is it possible, for example, to force Inkscape to retain a 'full' bounding box for an arc as if it were a full circle, to facilitate centre alignment?

Thanks, Trev

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up vote 1 down vote accepted

Here's a method that works on existing arcs. It takes a fair number of steps, and you can only do it to one arc at a time. For new projects, it's better to make all your arcs whole at the beginning, center them on each other, then change their angle endpoints.

Duplicate the arc (ctrl-D).

Switch to the arc tool (F5). Move the endpoints of the duplicate arc around so they don't overlap the original arc. (This is to make it easy to select them and keep it straight which is which.)

Switch to the object selector (F1) and select both arcs. Make them a group (ctrl-G).

Select the duplicate arc alone (ctrl-click).

Switch to the arc tool (F5). Click the "make whole" button.

Clear its fill and stroke (ctrl-shift-F).

Now the group contains your original arc and an invisible concentric circle of the same size, so its bounding box is as you want.

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Thank you Tom; this answer is very much appreciated. I will have a go with this shortly. – Trev16v Aug 28 '11 at 6:11

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