[sldev] Alpha Blending Settings Included in Texture Metadata

[nivardus]

I'm working on a patch that would essentially add image blending options to
a texture's JPEG2000 metadata. Specifically, I'd like textures to carry
their own alpha blending information: to switch between blending and masking
(like linden trees, so that it'd be possible for residents to make
transparent textures that sort correctly.) This would essentially be an
implementation of this jira issue:
http://jira.secondlife.com/browse/VWR-6713 Qarl Linden even mentioned in a
comment that there is even a LL internal jira entry for the same thing.

I'd like some input as to whether to include a simple boolean value that'd
be toggled during texture upload (Uploader can pick to have a texture
rendered with default settings, or masked with 0.5 alpha reject settings),
or adding more texture parameters for greater flexibility (Resident picks
from a selection of blend types, alpha comparison functions and correlating
values) I tend to lean in favor of allowing the deeper functionality to be
usable, so someone could play around with his textures' alpha reject
settings, seeing the more opaque areas stay while the more transparent ones
are cut away. But are there any risks I'm unaware of?

How kosher would including the blending value's native types into
LLImageJ2CImpl (llimagejp2c.h) and it's child classes be? (Including
llrender.h) Or should that be done at a higher level like at
LLImageJ2C::encode()?

Datatypes in question:
LLRender::eBlendType
LLRender::eCompareFunc
F32 value for above alpha rejection compare function

Any feedback/suggestions/warnings about the idea would be appreciated.

Toodles,
Gonta Maltz
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