How to plot large web-based heatmaps? I want to plot large heatmaps (say a matrix $500 \times 500$). I can do it in Python/matplotlib.pyplot with pcolor, but it is not interactive (and I need an interactive heatmap). I have tried with D3.js but what I found is aiming at displaying small heatmaps: http://bl.ocks.org/tjdecke/5558084
Naively extending this example with a bigger matrix (e.g. $500 \times 500$) can crash the web-browser.

So, can anyone point me toward a good way of displaying and interacting with large heatmaps with a web-based technology: I want to be able to interact on a web-page or a ipython notebook.
Plotly and Lightning are [supposedly] able to visualize extremely large data sets.