Preview outputs margin automatic fitting

[sheymann]

Following https://forum.gephi.org/viewtopic.php?t=1762&p=5996#p5996

Output in PDF/PNG/SVG should fit automatically, at least for the nodes.

[wumalbert]

I observe that currently the margin is assign with a fixed value. This should be automatically determined so as to adapt to the graph size. In my opinion, we can assign the margin according to bounding box of the graph, for example 10 percent of the width of the bounding box.

[vijeshm]

Yes, I've observed that as well. I used a slightly different approach suggested by wumalbert. If the user provides a margin that sufficiently contains the graph, the graph is exported as is. If the provided margin trims the graph, the approach will progressively increase the margin till it is completely contained. Apart from fitting the nodes, edges are fit.
PNG export before the fix:

PNG export after the fix:

The solution works if we have the rendered image in the form of a linearized pixels array. Unfortunately, I couldnt find anything equivalent to this structure in the case of PDF and SVG. Hence, I was not able to apply it in those cases. I've uploaded the code at vijeshm@628c995. Could anyone please verify the code and let me know if I could send a pull request?

[sheymann]

Can you make a pull request directly so that I'll assign a reviewer?

[vijeshm]

Sure. I'll do it right away.
Thanks.

[jersub]

Related to issue #239

[jersub]

Automatic fitting is fixed except for labels, cf. #1218.