How do I export a higher resolution image of a Mathematica Graph object?

Question

How do I export a re-sized version of the output I get from a call to GraphPlot (or TreePlot if they produce different output) to a jpg file?
Currently, I'm simply calling Export[file_name, G] where G is the result from a call to something like GraphPlot. I'm using Microsoft office picture manager to view the jpgs, but re-scaling them there yields unsatisfactory results due to poor resolution (the graph I'm trying to plot has strings as labels which can't be made out after rescaling this way). I would like to be able to choose the size/resolution of the rendered jpg.

Answer 1

As Simon already pointed out, don't use a raster-format for a vector-graphics. Instead, export you plot to e.g. a scalable vector graphics:

graph = GraphPlot[ExampleData[{"Matrix", "HB/can_292"}, "Matrix"]];
Export["graph.svg", graph]

The advantage is, that in such an image, you can still adjust and change lines, polygons and colors. And finally, you can export it to an image of arbitrary quality easily.

And remember, for Plots which contain lines, polygons, ... everything with sharp edges you should never use jpg. General speaking, this is a format for photographs only since its compression is made for reducing filesize in natural images. In those images you don't recognize the compression, in images with text, lines and polygons you certainly will notice the artefacts. Use png if possible. Take your browser and zoom into the above image.

Answer 2

You can set both image size and compression level of the exported file by doing something like

Export[file_name, G, ImageSize -> 1200, "CompressionLevel" -> 0]