It may be handy to encapsulate the channel logic in a public function that
looks like:
bool ImageBufAlgo::compatible_channels (const ImageBuf &A, const ImageBuf
&B,
bool allow_differing_alpha = false);
I have a feeling that a whole lot more of the functions you will implement will
need a similar comparison, so there's no point repeating the logic.
On Jun 12, 2012, at 12:09 PM, Larry Gritz wrote:
>
> On Jun 12, 2012, at 11:54 AM, Stefan Stavrev wrote:
>
>> 1. "If you have an ImageBuf::Iterator<BUFTYPE,float>, then *iterator will
>> always be float that you can just use."
>>
>> Will it always be in range 0-1?
>
> No. It will be the float conversion of whatever the input is. Certainly for
> half or float image files, it could be anything. (For anybody doing
> compositing, half is increasingly the usual case.)
>
>
>> 2. Since m_spec_valid and m_pixels_valid are protected I need to add a
>> method in imagebuf.h.
>>
>> bool uninitialized () const { return ! m_spec_valid && ! m_pixels_valid; }
>>
>> Is "initialized" negation of "uninitialized"? In this case initialized would
>> mean:
>>
>> m_spec_valid || m_pixels_valid
>
> Let's do it as "initialized" and then you can ask for "if (!
> ib.initialized())". I think that's more clear. Or you could do both, I
> don't mind.
>
>
>>
>> 3. "A channel with a labeled alpha channel should be assumed to be correct,
>> use it (any number of non-alpha channels are ok, as long as they match
>> between the two input images)."
>>
>> Hmm, ok I think I got it this time. So we handle the case of alpha channel
>> not specified, only for the two cases where number of channels is 3 or 4? In
>> other words, for number of channels 1,2,5,... fail if alpha channel is not
>> specified for both images? Don't assume any channel is alpha, don't assume
>> alpha is 1 everywhere.
>
> I think that is right.
>
> If there are 6 channels and none are alpha, it's anybody's guess whether
> alpha might be channel #3 (as if it were RGBA??), or if it's the last channel
> (XYZPQA), or if none are alpha. Just give up in that case.
>
> But if it's 3 or 4 channels and unlabeled, it will almost always be RGB/RGBA.
>
> --
> Larry Gritz
> [email protected]
>
>
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--
Larry Gritz
[email protected]
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