[Mesa-dev] [V4 PATCH 0/7] mesa: Naming MESA_FORMATs to a specification

[Kenneth Graunke]

On 01/23/2014 11:19 AM, Mark Mueller wrote:
> On Thu, Jan 23, 2014 at 2:24 AM, Marek Olšák <maraeo at gmail.com> wrote:
> 
>> On Thu, Jan 23, 2014 at 4:17 AM, Mark Mueller <markkmueller at gmail.com>
>> wrote:
>>> Hi Merek,
>>
>> I'm Marek.
>>
>>>
>>>
>>>
>>>
>>>
>>> On Wed, Jan 22, 2014 at 2:49 PM, Marek Olšák <maraeo at gmail.com> wrote:
>>>>
>>>> Hi Mark,
>>>>
>>>
>>
> [...]
> 
>>>
>>>
>>>> Also, I have a proposal for SRGB formats. MESA_FORMAT_SRGB_UNORM8 and
>>>> MESA_FORMAT_SA8B8G8R8_UNORM
>>>> look weird, because they are not really UNORM and there is also no
>>>> stencil. :) How about this: MESA_FORMAT_RGB_SRGB8 (denoting an array
>>>> format of the SRGB type and 8 bits per channel) and
>>>> MESA_FORMAT_A8B8G8R8_SRGB (denoting a packed format of the SRGB type).
>>>
>>>
>>> I agree it could be better. My reasoning for avoiding what you suggested
>> is
>>> that it creates an ambiguity between color information and storage type.
>> For
>>> instance, sRBG color space values could feasibly be stored as floats,
>> half
>>> floats, snorms, or unorms, could they not? Thus the S is a color
>> component
>>
>> I don't think so. An sRGB channel is always a byte. You cannot store
>> both linear and sRGB values in an 8-bit format without losing
>> precision for either one of them, which I think is why there are sRGB
>> formats for sRGB values and other formats for linear values. Bigger
>> texture types do not suffer from this limitation so much. Also, sRGB
>> is not very well defined outside of the range [0, 1], which leaves
>> UNORM as the only suitable type.
>>
> 
> That works for sRGB, but what about other color spaces that may be added in
> the future? I'm fine with leaving that to another day and with using the
> _SRGB decoration, as you say.

Oy.  Let's not worry about things that hypothetically could be someday.
 We need to do what makes sense today.

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