[whatwg] createImageData -> new ImageData() ?
kornel at osiolki.net
Tue Feb 12 14:07:38 PST 2008
On Sun, 10 Feb 2008 23:25:51 -0000, Ian Hickson <ian at hixie.ch> 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
> 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
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
ImageData can be made portable between canvases by adding aspect ratio
field or additional width/height fields given in CSS pixels.
regards, Kornel Lesiński
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