[whatwg] proposed canvas 2d API additions

Arve Bersvendsen arveb at opera.com
Mon Apr 24 02:53:34 PDT 2006

[ Ian Hickson ]
>> I don't understand how these are supposed to work when the underlying
>> bitmap's device pixel space does not map 1:1 to the coordinate space.

[ Vladimir Vukicevic ]
> I'm not sure what you mean -- the coordinates here are explicit canvas
> pixels, and they specifically ignore the current canvas transform.
> So, given
>  <canvas width="100" height="200"></canvas>
> the coordinates would be 0..99, 0..199.

Without expressing any other opinion at the moment, I'd just like to  
clarify how Opera's implementation of getPixel/setPixel currently follows  
the coordinate space, as Vlad is suggesting here, disregarding any  
translation and rotation. Given the following script snippet:

   gc =  
   for ( var y = 50; y < 100; y++){
     for (var x = 50; x < 100; x++){

... with this CSS:

   canvas  {
     width: 200px;
     height: 200px;
     border: 1px solid black;

and the following markup:

   <canvas width="100" height="100">

we fill the bottom-right quadrant of the canvas, with a rectangle that is  
comprised of 100x100 CSS pixels.

Arve Bersvendsen, Opera Software ASA

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