Re: Review: added ociobuildicc app


Joseph Slomka <jsl...@...>
 

Malcolm,

When building ICC profiles I've found it very helpful to use the InputTables of the AtoB0 to hold an intermediate conversion, for instance the a 1024 entry 1-d conversion from Cineon to video . The CLUT can then just hold the 3d portion of the conversion I found the match was much improved going that way without having to create a large 3d lut. It's really helps out if you are working with linear space source files in Photoshop.

It may be handy to specify that intermediate space to be placed in Add3GammaCurves()

So for example,
Source=Cineon
DST=Srgb_Film
Intermediate=video10

could be broken into 2 OCIO transformations
one transformation from Cineon to video10. (This transformation would be 1024 entries and placed into the 52nd byte of the Lut16 structure)
The next transformation would be the video10 to Srgb_Film, placed in the CLUT , at the end of the InputTables list.

It looks like that you are creating a gamma 1.0 table in that spot right now.

Let me know if that makes sense.

-Joseph

-----Original Message-----
From: ocio...@... [mailto:ocio...@...] On Behalf Of Malcolm Humphreys
Sent: Thursday, January 27, 2011 11:00 PM
To: ocio...@...
Subject: Re: [ocio-dev] Review: added ociobuildicc app

Also added Little CMS to LICENSE file

Commit:
https://github.com/malcolmhumphreys/OpenColorIO/commit/8ff296f8ab234ea7b06704036037bf2a132ebd6a

.malcolm

On 28/01/2011, at 5:49 PM, Malcolm Humphreys wrote:

Attaching some slightly larger examples :)


On 28/01/2011, at 5:46 PM, Malcolm Humphreys wrote:

Added ociobuildicc app which will build a soft-proofing icc profile for a given working space.
(added LCMS2 into ext)

Commits:
https://github.com/malcolmhumphreys/OpenColorIO/commit/1b0d39fb10db10
f4edbf1fb0fed124b548b836d9

Attached is an example of two profiles in action.

From the left
* sRGB reference image (ocio cpu)
* matte paint allocation space
* log space image.

The visual difference in the log image is most likely caused by 16bit
quantization errors in the CLUT of the AToB0Tag. These errors are
less with the matte paint allocation as the distance to travel is less.

I did play around with supporting the new MPE D2Bx and B2Dx tags
which should make this problem go away
(http://www.color.org/ICCSpecRevision_02_11_06_Float.pdf) but couldn't get it too work reliably so I pulled it out till I can.

.malcolm



<ocioicc_softp_off.jpeg><ocioicc_softp_on.jpeg>
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