As of November 2014, I am still running LibreOffice 3 on Linux and do not have direct chart graphics export capability, but there is a fairly easy workaround. With Inkscape installed on the computer, I export the chart from Calc to a PDF file, then extract the chart from the PDF using Inkscape. This allows one full freedom to manipulate the graphics in vector format, then export as PNG or save as SVG for use in other applications.
- Click on the chart in LibreOffice Calc to select it; eight small, green squares appear around the edges.
- In the menu bar, click File > Export as PDF…
- In the PDF Options dialog, select Range: “Selection”, then click on the Export button and save the PDF file.
- Start up Inkscape and import the PDF file thus generated. It should contain only the chart, not the spreadsheet, with all graphics in a single group.
- Ungroup everything and delete the page header and footer text, if it is there, plus any objects not needed for your target application.
- Some objects, such as grid lines and tick marks on the axes, may not be visible, because they have no fill or stroke assigned to them, but this can be corrected in Inkscape with the Fill and Stroke toolbox.
Once the fix-ups are done, save the image in SVG format, and if desired, export a copy in PNG format at the desired scale. Using vector graphics allows the chart image to be scaled practically without limit, yet preserving smooth, clear appearance at all scale factors.
Free Inkscape binaries are available for most popular operating systems, including Linux, Mac OS X, and Microsoft Windows.