How to use Selenium with "chart.js"

I've been asked to use Selenium to write some tests for a website. Several of the pages have graphs on them that are generated by the "chart.js" library. The tests require me to:

• Read the size of some of the data values in the chart
• Click on certain bars on the chart.
• Hover over certain bars and validate the tool tips

The trouble is the chart is implemented as a single HTML canvas element, so there is no DOM for the details of the chart that selenium can manipulate.