On Sun, 10 Feb 2008 23:25:51 -0000, Ian Hickson <[EMAIL PROTECTED]> wrote:
That would mean that passing ImageData around between two <canvas>
elements doesn't always work as expected. I think that's highly
undesirable. Is there any implementation where we know this will the
case?
Not today, but why preclude it? Implementations could get higher quality
renderings on canvases that get resized dynamically, by using a bigger
backing store. What's wrong with what we have now?
It's very easy to write code which assumes that size of imageData is the
same as size given in <canvas width height> (I know, because I did it :)
Since the ratio is system/browser-dependent and 200dpi screens aren't
popular yet, such bug may be easily overlooked/ignored and get widely
deployed.
The difference in sizes isn't intuitive. For example if browser doubled
number of pixels in ImageData only when user used zoom, I think authors
would rather think that browser's zoom is buggy.
I think that by default getImageData should return data with same size as
specified in width/height attributes of <canvas>. There might be another
method (getImageScreenData?) or method argument that returns all pixels of
<canvas>.
ImageData can be made portable between canvases by adding aspect ratio
field or additional width/height fields given in CSS pixels.
--
regards, Kornel Lesiński
