getImageData and other canvas APIs randomly regressing in performance is a common occurrence, sadly. Google frequently makes changes to the 2D graphics stack an

getImageData and other canvas APIs randomly regressing in performance is a common occurrence, sadly. Google frequently makes changes to the 2D graphics stack and they don't test a wide set of scenarios, just particular cherry-picked ones. Back when I still maintained some games using canvas it was pretty typical to see my framerates shift wildly every 6 weeks when a new release rode the trains. Two other scenarios that will often change in performance is canvas-to-canvas draws and canvas<->WebGL interop, because how those are implemented is complex. In the past particular behaviors would instantly disable hardware acceleration for a given canvas, tanking your performance.