If you need to insert a SmartSheet generated Gantt chart in to PowerPoint, the following procedure is useful:

• Output the Gantt to a PDF at A3 size or above, and try to get it all on one sheet.
• Issue the following command to generate a PNG of the chart:
  convert -density 300 -trim INPUT.pdf OUTPUT.png

The -density 300 option means it is generated at a high enough resolution for most purposes and the -trim option gets rid of all the white-space around the chart.

And voila, a nice crisp high-res PNG that will look good on your slide.