Canvas: Exporting Image problem

So I'm trying to play around with the Canvas docs to see whether I understand them and will find them useful. I created the canvas below (please don't analyze it too closely) just to get an idea how it works.

Then I exported it so I could see what it would look like on a power point slide. This is what I got (for what it's worth, I tried saving it in PNG and JPEG formats):

So why isn't it the same?