[whatwg] Canvas draw quality

[David Hyatt]

Except with something like canvas, people are going to care about the  
precise pixel-level details of the rendering.  We can't handwave  
these details away using vague terminology like low-quality or high- 
quality, where the user agent is free to decide what those terms  
mean.  If we do that, then we risk not having interoperability  
between browsers.

dave

On Oct 20, 2006, at 10:44 PM, Andrew Fedoniouk wrote:

> Dave, various implementations use different libraries/approaches  
> for the Graphics.
> Way of tuning parameters and their set can be different. I think  
> that it is simply not possible
> to generalize them all. At least something generic like  
> preference=quality/speed switch makes real sense.
>
> Technically it is better to allow to get two Graphics instances for  
> the same canvas and use
> them at the same time if really needed. In any case 2D and 3D  
> graphics shall coexist on the same surface.
> So why not 2D and 2D-fast ?
>
> In any case it is up to UA to provide multiple implementation for  
> different values of contextID.
> contextID as a string is there in purpose I belive. That is the one.
>
> Andrew Fedoniouk.
> http://terrainformatica.com
>
>
>
>
>
> ----- Original Message -----
> From: David Hyatt
> To: Andrew Fedoniouk
> Cc: Benjamin Joffe ; whatwg at whatwg.org
> Sent: Friday, October 20, 2006 10:12 PM
> Subject: Re: [whatwg] Canvas draw quality
>
> I don't think a totally different context is a good idea.   
> Sometimes you want to mix antialiased and non-antialiased modes.
>
> The API in CG is part of the graphics state...
>
> CGContextSetShouldAntialias
>
> I don't think an API like this should be vague about what it's  
> doing... e.g., just using vague terms like "quality."  We should  
> say what we mean... antialiasing for example.
> dave
>
> On Oct 20, 2006, at 10:01 PM, Andrew Fedoniouk wrote:
>
>>
>> ----- Original Message -----
>> From: Benjamin Joffe
>> To: whatwg at whatwg.org
>> Sent: Friday, October 20, 2006 9:09 PM
>> Subject: [whatwg] Canvas draw quality
>>
>> I would like to see a property added to the 2d canvas context that  
>> would allow quality to be lowered for drawing functions. Normally  
>> any time a shape is drawn, pixels close to the boundary are made  
>> semi transparent to make it look smooth, this is usually  
>> favourable but I have had a need to draw shapes and lines with  
>> pixel sharp boundaries in the same way as Java normally does. I  
>> would imagine that with the setting enabled, only the integer part  
>> of linewidth would be used. This setting would also affect drawing  
>> images, making them have no blurring or approximating when scaled  
>> or rotated.
>>
>> This could easily be implemented without affecting old scripts,  
>> making a property such as lowQuality = true; (default false). Or  
>> perhaps allowing more control: a float from 0 (low quality) to 1  
>> (high quality), and interperating null as 1 for backwards  
>> compatibility.
>>
>> This property could also be handy in instaces where both fill()  
>> and stroke() are being called. Low quality could be used on the  
>> fill() to improve performace while stroke() could be used with  
>> high quality so it still draws smoothly.
>>
>> I think that the best way is just to define different values for  
>> the context ID:
>> DOMObject getContext(in DOMString contextID);
>> Something like "2D" and "2D-fast" or "2D-simple".
>> Another option would be to add one optional parameter to the  
>> getContext() function.
>>
>> I doubt that someone will need to switch it in the middle of  
>> drawing so
>> having such switch as an attribute is redundant.
>>
>> Andrew Fedoniouk.
>> http://terrainformatica.com
>>
>>
>>
>>
>
>

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