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fix primaries used for display p3 gamut #331

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merged 1 commit into from
Dec 3, 2024

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  • luminance function for p3 gamut is using weights of dci p3 instead of display p3. this is corrected. accordingly the gamut conversions involving display p3 are updated.
  • increased precision of some constants used in csc

Test: ./ultrahdr_unit_test

@ram-mohan ram-mohan changed the title fix primaries using for display p3 gamut fix primaries used for display p3 gamut Nov 22, 2024
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LGTM. Thank you!

@ram-mohan ram-mohan force-pushed the p3primaries branch 2 times, most recently from 94ada70 to c44bd39 Compare November 26, 2024 19:31
- luminance function of p3 gamut is using weights of dci p3 instead of
  display p3. this is corrected. accordingly the gamut conversions
  involving display p3 are updated.
- increased precision of some constants used in csc

Test: ./ultrahdr_unit_test
Change-Id: Iec77b3d24adb7ad887a8f53d805eecc0c0160f28
return {{{1.34369f * e.r + -0.28223f * e.g + -0.06135f * e.b,
-0.06533f * e.r + 1.07580f * e.g + -0.01051f * e.b,
0.00283f * e.r + -0.01957f * e.g + 1.01679f * e.b}}};
return {{{1.343578f * e.r + -0.282179f * e.g + -0.061399f * e.b,
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Could you double check if this matrix is correct?

I use
[2.4934969119,−0.9313836179,−0.4027107845; −0.8294889696,1.7626640603,0.0236246858; 0.0358458302,−0.0761723893,0.9568845240;] x [0.636958,0.144617,0.168881; 0.262700,0.677998,0.059302; 0.000000,0.028073,1.060985;]

and got this: (maybe I am wrong)

[ 1.33736487 -0.33736476 -7.08830856e-07 ] [ 0.02128283 0.97871719 -1.14552781e-07 ] [ 0.00418868 0.03418871 0.99581128 ]

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the matrix multiplication seems to be wrong. The individual matrices are same as the ones i am using.

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OK I re-did the math with gemini and this time the result matches with yours. My previous result with chatGPT was wrong. Sorry for the confusion.

return {{{1.34369f * e.r + -0.28223f * e.g + -0.06135f * e.b,
-0.06533f * e.r + 1.07580f * e.g + -0.01051f * e.b,
0.00283f * e.r + -0.01957f * e.g + 1.01679f * e.b}}};
return {{{1.343578f * e.r + -0.282179f * e.g + -0.061399f * e.b,
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OK I re-did the math with gemini and this time the result matches with yours. My previous result with chatGPT was wrong. Sorry for the confusion.

@DichenZhang1 DichenZhang1 merged commit 2b73304 into google:main Dec 3, 2024
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@ram-mohan ram-mohan deleted the p3primaries branch December 3, 2024 19:55
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2 participants