Improve gainmap coefficients signalling accuracy

google / libultrahdr

Ultra HDR is a true HDR image format, and is backcompatible. libultrahdr is the reference codec for the Ultra HDR format. The codecs that support the format can render the HDR intent of the image on HDR displays; other codecs can still decode and display the SDR intent of the image.

https://developer.android.com/guide/topics/media/platform/hdr-image-format

Apache License 2.0

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Improve gainmap coefficients signalling accuracy #191

Closed ram-mohan closed 3 months ago

ram-mohan commented 4 months ago

add rounding factor to gainmap coefficients before converting them to 8 bit ints
capture min and max content boost basing on the computed gainmap coefficients and use them during affine mapping
use hdr offset and sdr offset to effectively signal hdr black
add option to configure maxCLL of hdr intent

Test: ./ultrahdr_unit_test