How can I save a Calc chart as high-resolution graphics?

Using LO 5.3.2, I have some Calc charts, which I would like to save as high-resolution graphics. Within Calc, I can right-click on the chart and save it as an image. But I have problems getting a high resolution.

If I save as a bitmap format (BMP, PNG, GIF, …) then resolution is about the same as on screen, which is too poor for printing.

Alternatively, I can save the graphics as a vector format (e.g. SVG or EMF) to obtain full resolution of lines and text. But I need it to be more common format, like the bitmap formats mentioned above. I have tried loading the vector file into Draw and export it in a bitmap format. But with limited success - I can set a high resolution, but then just gets a small image.

Thus the question: How can I save a Calc (or other) chart as high-resolution graphics?

You can work on old OpenOffice work-around:

Copy diagram > paste in Draw > enlarge Draw page to A2 or similar > convert diagram to metafile > enlarge (proportional) > safe selection as png (in high resolution)

Conversion in metafile or curves gains the advantage that also legends are increased if one enlarges the entire object. This does not happen on enlarging in Calc or Draw itself as native Calc object. (I hope I could explain understandably.)