[whatwg] getImageData(), the canvas backing store, and device pixels != CSS pixels

Edward O'Connor eoconnor at apple.com
Thu Sep 29 16:22:47 PDT 2011


Re: http://krijnhoetmer.nl/irc-logs/whatwg/20110930#l-81

An example in § Pixel Manipulation[1] states that "the data
returned by getImageData() is at the resolution of the canvas backing
store, which is likely to not be one device pixel to each CSS pixel if
the display used is a high resolution display."

This should probably be moved out of the example and into the main prose
of the spec. It's easy for implementors to overlook normative statements
made in examples.


1. http://www.whatwg.org/specs/web-apps/current-work/multipage/the-canvas-element.html#pixel-manipulation

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