[Bug 11517] Since context.putImageData() does not handle compositing, another set of methods, maybe context.drawImageData(), should be created to allow ImageData objects to be drawn onto the canvas in the same fashion as Image objects.

https://www.w3.org/Bugs/Public/show_bug.cgi?id=11517

--- Comment #7 from Sirisian <warcraftthreeft@sbcglobal.net> 2012-03-01 17:34:02 UTC ---
I can't really remember why I suggested this. It was probably because of a
performance problem when rendering images. That is to say the intended
implementation of drawImageData would composite but only on integer values so
as to not take the performance hit that drawImage has when the x and y values
are rational and there is no transformation applied. However, a drawImage
implementation could special case for that to draw faster so such a method for
drawImageData seems pointless. The other perceived problem was handling of
alpha values that are binary either on or off. drawImageData would ideally be
designed to render only pixels with an alpha that isn't 0 so that no
performance is lost due to a software blending function. That is to say the
implementation of drawImageData would be identical to putImageData except it
would not copy pixels that have an alpha value of 0. Kind of a random
proposition for the sake of a sane and fast implementation. More of an edge
case in the usage of canvas.

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Received on Thursday, 1 March 2012 17:34:06 UTC