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HI

I have a question about the function BGRtoLAB

for LAB, there is a case condition specified in the Manual:

L = 903.3 * (Y/Y_{n})^{1/3.} for `Y/Y _{n} ≤` 0.008856

Now, if I take the border case , 0.008856^(1/3) is ~0.207, -> mult 903.3 = ~187

This value is converted to range of 0..255 by factor 2.55, so we get 476 which is way out of range.

Actually i run into this condition (Y/Y_{n} ≤ 0.008856) for values like R=0, G=0, B=10 which is pretty dark, L should be Close to 0 also

So what is wrong with your formulas?

thx & BR

Stefan

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Hi again

found some other formulas. I think it should be without Exponent ^(1/3) like in the f(t) formulas:

L = 903.3 * (Y/Y_{n})^{.} for Y/Y_{n} ≤ 0.008856

as 903 is the factor 7.787*116

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Thank you for reporting the issue,

We will investigate it.

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Yes, have a look. the code is ok, the results are ok of the ipp, just the doku

also in the f(t) formula something is wrong, as f(t) is around ~1 you probably won´t substract 16 and multiply later the result .... . It´s all messed up

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**the code is ok, the results are ok of the ipp, just the doku**

What is "doku"? Besides, what does "**the code is ok, the results are ok of the ipp**" mean? Your program works OK with the IPP function BGRtoLab?

Is this a “theoretical” question? Or could you provide us with a test image and a sample code that can reproduce the problem that you encountered, please?

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Yes, the code works, the results are ok

only the documentation (docu, doku) is horribly wrong (the named formulas)

BR

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OK. Got it. Thank you for reporting the issue.

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