Alright, this is now in the list of "desired features" for next
releases. 2.7 release candidate will be out in days, so this would
eventually make its way on 2.8 or maybe will take a little bit more.
The difficulty is in keeping backwards compatibility, actually lcms
skips over alpha channel, this is documented and somebody may use this
behavior.
Workarounds are to use same buffer for input and output or to copy
full buffer prior color manage it.
Regards
Marti Maria
The LittleCMS project
http://www.littlecms.com
Quoting Terence Tay <terence...@gmail.com>:
> Noel,
>
> I've run into the same issue as you and I would find the option you
> described to color-manage RBGA images in an out-of-place manner very
> useful.
>
> Terence
>
>
>> On Feb 1, 2015, at 9:02 AM, Noel Carboni
>> <ncarb...@prodigitalsoftware.com> wrote:
>>
>> Hi Marti / Open Source Developer(s),
>>
>> As always, thank you for publishing your excellent LittleCMS library.
>>
>> Virtually all we use LittleCMS on are RGBA images. One of the
>> things we have to do now is handle the unused field (A) separately.
>>
>> Would it be possible/reasonable to add an option to LittleCMS so
>> that it would simply carry through unused A values without
>> modification (or with a simple format change, per the format specifiers)?
>>
>> As it is now we have to copy the data first, then color-manage it,
>> but it would be nice to be able to have a single function
>> (embodying a cmsDoTransform call) that would copy / color-manage /
>> format-convert ALL the data in one pass. We already have
>> workarounds implemented, but having it all done at once by
>> LittleCMS would better serialize RAM access and save some computer
>> time.
>> On today's powerful multi-core machines RAM bandwidth can be a bottleneck.
>>
>> If you are open to the idea of adding this functionality to the
>> product, I may be able to allocate some time to help with the
>> implementation.
>>
>> If you are a LittleCMS user on the mailing list who would also like
>> to see this addition, please let us know.
>>
>> Thanks.
>>
>> -Noel Carboni
>> ProDigital Software
>>
>>
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