[haiku-bugs] Re: [Haiku] #2946: BGradient does not support alpha transparency
- From: "stippi" <trac@xxxxxxxxxxxx>
- Date: Thu, 24 Jul 2014 09:54:25 -0000
#2946: BGradient does not support alpha transparency
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Reporter: sdeken | Owner: stippi
Type: bug | Status: new
Priority: normal | Milestone: R1
Component: Kits/Interface Kit | Version: R1/pre-alpha1
Resolution: | Keywords:
Blocked By: | Blocking:
Has a Patch: 0 | Platform: All
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Comment (by stippi):
B_OP_ALPHA can mean "use the constant alpha of the high color", or it can
mean "use the alpha of the source pixel/color". Perhaps you have to set
B_PIXEL_ALPHA as the alpha function as well? I think B_CONSTANT_ALPHA may
be the default.
Also, try with B_OP_OVER once. For BBitmaps, B_OP_OVER works very similar
and perhaps more intuitively than B_OP_ALPHA. I don't know whether the
same span line blending function is resolved in the DrawingMode when
drawing gradients and when drawing bitmaps, but I would expect it to be
so. And I don't remember whether B_CONSTANT_ALPHA completely ignores the
source pixel alpha for BBitmaps, or multiplies it, making B_CONSTANT_ALPHA
(the alpha value of the current high color) work like a global alpha value
which is multiplied with the pixel value of BBitmaps. IIRC, we have
already established in another context that this would be nice but does
not currently work that way.
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Ticket URL: <https://dev.haiku-os.org/ticket/2946#comment:5>
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