Change in EXR open from CS2 to CS3 can this be fixed?

I think we should not adhere to any specifications. That way we all can all do what we want - kind of like how the product is packaged and sold... Makes perfect sense to no one and everyone is happy.

You know what this whole discussion reminds me off?

I once sat in a train, across the corridor there was a family sitting at a table with the kid (maybe 4-5 years old) drawing with color pencils, the father reading a a paper and the mother reading a book.
Suddenly the father reached out and bashed the kid HARD in the face yelling: "There is no such thing as a green dog".

One of the most shocking experiences I ever had.

Once upon a time, software was developed for the user who paid money to get things done faster and more flexible.

If a software company representative tells me that what I want is wrong, not to spec, that I have no clue about compositing if I even think about using a channel for something else as what somebody defining a file format intended ( but most probably never intending as rigid an interpretation) and that many many people will suffer from extreme confusion if they are presented with a choice about how a channel should be interpreted somewhere in advanced preferences, I can only walk away with a very irritated feeling of extreme absurdity.

I highly respect everybody here, but pussyfooting around a guy who simply is using his position of assumed "power" to tell everybody off and that "there is no green dog" is absurd.

Chris: may you live a long, full and happy live as far from the specs as possible. :-)

Carpe Diem and best Regards,

Thomas Helzle

> No, many file formats are not premultiplied,
> and some file formats support an alpha channel
> that has nothing to do with transparency/opacity.

Apologies for being unclear, I expressed myself sloppily.

I meant to say, for all format that support a *premultiplied* alpha channel, the *meaning* of premultiplied should adhere to what was just defined for OpenEXR, i.e. that the color (1,1,0,0) is valid, and means "luminescent yellow".

> TGA is not premultiplied (some people think it
> supports opacity, and some don't).

Well, the TGA specification supports all variants, if you go back and read it. Quoting from it:

Byte 494 - This single byte field contains a value
which specifies the type of Alpha channel data contained
in the file.

Value Meaning
0: no Alpha data included (bits 3-0 of field 5.6
should also be set to zero)
1: undefined data in the Alpha field, can be ignored
2: undefined data in the Alpha field, but should be retained
3: useful Alpha channel data is present
4: pre-multiplied Alpha (see description below)
5 -127: RESERVED
128-255: Un-assigned

> PNG is not premultiplied, and only supports opacity.

Correct. One of the main failings of PNG, I might add, and probably why it isn't used nearly at all by CG professionals, other than maybe for painting textures.

> Just because the format has a place for some extra
> data - that does not mean that the format supports
> your interpretation of the data. Most file formats
> are pretty specific about how the data should be
> interpreted, but some are not, and some (TGA) have
> grown a following of users who just ignore the
> specification entirely.

Well, there is this thing known as "de-facto standards" as well. I would rather say that the interpretation of alpha in TGA files has matured and evolved.

For example, the original TGA spec (quoted above) simply directs you back to the original SIGGRAPH 1984 Duff & Porter paper on premultiplied alpha. Did Duff & Porter think about the luminescent yellow color? No, they didn't.

Does that give anyone the right to assume it is "illegal"? No.

/Z

I also thing there is a misunderstanding of the pre vs straight. The data is written the same, but the data before it's written is different in each case. Therefore a format can carry pre or straight, but the image data written is different. You can't bounce between the two after they've been written but you can beforehand. I can choose to save pre or straight on the point of saving to TGA. The image looks the same before I do that, but the results are different, yet either straight or pre, the file is still RGBA.

Oh I agree... not trying to...

But lets just say we've been down this road with other formats before ;)

LOL. Hey "progress", how about starting another thread with your last post? You could title it something like Dead Horse.

I think the discussion has progressed well beyond these points and is going in a very positive direction. Let's not impede the effort at this point eh?

Users only use what is programmed Chris... if you wish to bang the standards drum, bang it to other developers, but trying to shut the stable doors when 1/2 the world are riding the herd and asking them to come back isn't going to work... especially when it's within the same product.

As I keep saying. Alpha is a representation of opacity. It is not opacity per se. If that was the case it would be impossible to have something at 0% opacity with an RGB value... but it isn't.

It's really simple. Removing the alpha shouldn't take the RGB values with it.

Now, if you say these RGB values still exist, and that it's possible to get them back even though the A is no longer accessible, then let's have that functionality.

Just because a format is premultiplied doesn't mean you can chuck the alpha willy nilly. It still serves a purpose, even as opacity.

But you can't go around 'fixing' things that people have learnt to work with in a productive manner. Well not if you want the quiet life, or the nod of approval from those that lead the industry.

Call it serendipty, whatever, but it worked before, it's been shown to work with plugins, it's simple it's current state that's broken. I can hoop jump to fix it, but what's the reason that I have to do that except your interpretation of something...?

There seems little point in sticking with something that breaks the interest of so many.

If Adobe is interested in an expanding market, perhaps it should think about not shrinking the one it has. Given the nature of HDR images, it's not like it's something the novice user is going to care about.

It's another reminder of how out of touch Adobe have become with their user base.

No, many file formats are not premultiplied, and some file formats support an alpha channel that has nothing to do with transparency/opacity.

TGA is not premultiplied (some people think it supports opacity, and some don't).
PNG is not premultiplied, and only supports opacity.
TIFF is premultiplied if you use opacity (associated alpha), and not if you only use unassociated alpha channels (because they aren't opacity, the color data cannot be premultiplied).

Just because the format has a place for some extra data - that does not mean that the format supports your interpretation of the data. Most file formats are pretty specific about how the data should be interpreted, but some are not, and some (TGA) have grown a following of users who just ignore the specification entirely.

i I'm really happy this discussion is getting somewhere.

Likewise.

Special thanks to Florian & Chris and their professional ability for being able to the point through the heat haze.

Now Chris, how do I get onto the beta?

I'm really happy this discussion is getting somewhere. Special thanks to Florian.

And that Chris (& Adobe) is finally seeing the light of what "premultiplied" really means. (Perhaps even luminiscent yellow light ;) )

I do however hope everyones understands that this definition of "premultiplied" applies to every format with an alpha channel, i.e. TGA's, etc. etc, i.e. 1,1,0,0 is a legal color in a TGA file as well (well, it'll probably be 255,255,0,0 but you get the idea).

/Z