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Re: [E-devel] Evas and alpha premul color data
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From: <jos...@ju...> - 2006-06-23 14:09:32
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= > It would certainly break a lot of my code. I currently have some = > manual bindings of various evas objects to Ruby, and large chunks = > of code that implicitly require nonpremultiplied alpha. = > = Yes, it would. You would have to premul the data prior = to handing it to evas. = = > I suppose using premultiplied alpha would also break things like = > loading ARGB32 data directly from Imlib2 to Evas by hand = > (I frequently use that method to display images), since IIRC PNG = > data for example is not premultiplied. = = Evas can load png images.. Why do you need to use imlib2 = to load them? = = > Also, I frequently use an 'evas-cairo' object of my own that = > simply uses an evas image as its surface and responds to cairo = > calls (I mostly use this for displaying SVGs in Evas and as a = > fallback for gradients since they got broken in Evas). = = Gradients are still broken? Ummm... They seem to work = "ok" for me (in the very limited tests I've had a chance to put = them thru). What problems exactly are you having with them? = = > For this reason I explicitly implemented a de-premultiplier = > (since cairo uses premultiplied alpha on its surfaces as well). = = Well, you wouldn't need that then, as evas would expect = premul data as well. = Also, why do you need both imlib2 *and* cairo to 'draw' = stuff? What are you drawing with imlib2 that cairo can't? = = > Additionally I have several routines that 'drop-shadow' and = > 'reflect-shadow' some Evas images by accessing the buffer itself, = > so that would also break with premultiplied alpha. = = They may not need any changes.. check the code and see = wether or not you really need non-premul for the algos to work, = or if they may just need minor changes. = = > I wouldn't recommend against it, but I'd highly prefer some = > global flag which can be set that would allow developers to = > choose between the two. Or if necessary, a flag on an object- = > per-object basis that can be overridden if needed. = > = > Greets, = > Robin. = = A flag to set wether or not the data you set or get = is premul would in effect be useless to evas if it's only = going to work with premul data internally -- all evas would = do is premul or un-premul the data.. might as well do that = yourself.. = The point is that non-premul data is a pain to deal = with and should be avoided - move your work over to premul = and you may be happier :) = = = jose. = |