[whatwg] getImageData/putImageData comments

Maciej Stachowiak mjs at apple.com
Mon Jun 1 00:13:04 PDT 2009

On May 31, 2009, at 9:08 PM, Robert O'Callahan wrote:
> Here are a couple of relevant threads:
> http://lists.whatwg.org/htdig.cgi/whatwg-whatwg.org/2007-May/011284.html
> http://lists.whatwg.org/htdig.cgi/whatwg-whatwg.org/2008-February/013906.html
> Then there was a discussion on #whatwg more recently.
> http://krijnhoetmer.nl/irc-logs/whatwg/20090326#l-263
> So far it seems the data supports the hypothesis that authors expect  
> getImageData to return 1 image pixel per CSS pixel and their scripts  
> break when that's not true. That won't change until authors all have  
> high-dpi screens.

I'm not surprised. On the other hand, if we use CSS pixels, it won't  
be possible for authors to get it right, even if they do have high-dpi  
screens. It might be wise to have separate APIs (or a distinguishing  
parameter) to indicate whether you want scaled or true resolution.  
That way, unaware code gets a resolution loss, but aware code can do  
the right thing. I guess you suggested something like that in the IRC  
conversation you cited.


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