Thought about it a bit more. If you've got a 100x100 grid there, and if you're actually calling drawImage on the backend, then maybe low fps is to be expected kind of. Perhaps now is the time to dip your toes into WebGL? Have you seen my tool ArrowBench? :)
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I'm not using drawImage. You're right - it's way too slow. I copy the canvas buffer array and put on pixel by pixel to that array. It's only using a low amount of percentage of your CPU because it's single threaded and probably using 100% of one core. I need to look into WebGL for sure. I just like working out the math for these myself, but I gotta stop doing that and start using at least a graphics library or maybe even a game library. I'll check out ArrowBench, thanks!