Hi,
I am writing to this list in hope of getting some help for crafting
profiles with LittleCMS. My objective is to craft a Rec.709 YCbCr to XYZ
profile for Krita. The YCbCr -> XYZ conversion goes as this:
1. YCbCr -> normalized R'G'B. Source: Ford & Roberts (1998), eq. 105.
<http://poynton.ca/PDFs/coloureq.pdf>
2. Normalized R'G'B -> linear RGB. Source: ITU-R BT.2087
3. Linear RGB -> XYZ. Source: Ford & Roberts (1998), eq. 102.
<http://poynton.ca/PDFs/coloureq.pdf>
And for the XYZ -> YCbCr side of things,
1. XYZ -> Linear RGB. Source: Ford & Roberts (1998), eq. 103.
<http://poynton.ca/PDFs/coloureq.pdf>
2. Linear RGB -> Normalized R'G'B. Source: ITU-R BT.2087
3. Normalized R'G'B -> YCbCr. Source: Ford & Roberts (1998), eq. 104.
<http://poynton.ca/PDFs/coloureq.pdf>
My questions are as follows:
1. Are the pipelines correct? If not, what are the errors?
2. According to the ICC 4.3 standard, sections 10.10.1 and 10.11.1, to
use the CLUT I must wrap it in two triplets of (identity) tone curves.
But doing so simply renders the pipeline into an empty tag, so I need to
downgrade to 2.2 and remove the tone curves from the pipeline. Why is
this happening?
If anyone wants to check my code out, I have uploaded it at
<https://github.com/amyspark/krita-ycbcr-profiles>. Please reply to this
email with any questions you may have.
Best regards,
amyspark
--
amyspark 🌸 https://www.amyspark.me
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