[whatwg] [canvas] imageRenderingQuality property

David Hyatt hyatt at apple.com
Mon Jun 2 14:26:41 PDT 2008

I like the idea of this property.  I actually would love to see the  
SVG property applied to HTML <img> as well. :)


On Jun 2, 2008, at 4:15 PM, Vladimir Vukicevic wrote:

> Sure; bilinear filtering is slower than nearest neighbour sampling,  
> and in many cases the app author would like to be able to decide  
> that tradeoff (or, at least, to be able to say "I want this to go as  
> fast as possible, regardless of quality").  Some apps might also  
> render to a canvas just once, and would prefer to do it at the  
> highest quality filtering available even if it's more expensive than  
> the default.
>    - Vlad
> On Jun 2, 2008, at 12:25 PM, Oliver Hunt wrote:
>> Um, could you actually give some kind of reasoning for these?  I am  
>> not aware of any significant performance issues in Canvas that  
>> cannot be almost directly attributed to JavaScript itself rather  
>> than the canvas.
>> --Oliver
>> On Jun 2, 2008, at 12:19 PM, Vladimir Vukicevic wrote:
>>> I'd like to propose adding an imageRenderingQuality property on  
>>> the canvas 2D context to allow authors to choose speed vs. quality  
>>> when rendering images (especially transformed ones).  This is  
>>> modeled on the SVG image-rendering property, at http://www.w3.org/TR/SVG/painting.html#ImageRenderingProperty 
>>> :
>>> attribute string imageRenderingQuality;
>>> 'auto' (default): The user agent shall make appropriate tradeoffs  
>>> to balance speed and quality, but quality shall be given more  
>>> importance than speed.
>>> 'optimizeQuality': Emphasize quality over rendering speed.
>>> 'optimizeSpeed': Emphasize speed over rendering quality.
>>> No specific image sampling algorithm is specified for any of these  
>>> properties, with the exception that, at a minimum, nearest- 
>>> neighbour resampling should be used.  One alternative is to  
>>> specify 'best', 'good', 'fast', with "good" being the default, as  
>>> opposed to the SVG names; I think those names are more  
>>> descriptive, but there might be value in keeping the names  
>>> consistent with SVG, especially if that property bubbles up into  
>>> general CSS usage.
>>>  - Vlad

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