getImageData is not color-corrected to a profile known by the page, then it cannot be used. The pixel values are technically undefined and unknown, and app can only assume the profile is reasonably close to sRGB (and the more unusual the profile is, the worse color skew it'll cause).
This would be terrible for photo editing applications that need to use asm.js &
getImageData almost exclusively, and have to have high quality color at the same time.
getImageData is left in color space of the display, which is then made known via some other means, then it's a vector for fingerprinting and cross-browser persistent tracking ).