On Tue, 23 Dec 2025 16:44:48 -0300 Nícolas F. R. A. Prado <[email protected]> wrote:
> Introduce definition of a hybrid log-gamma electro-optical transfer > function for 1D Curve colorops. > > Signed-off-by: Nícolas F. R. A. Prado <[email protected]> > --- > drivers/gpu/drm/drm_colorop.c | 1 + > include/drm/drm_colorop.h | 10 ++++++++++ > 2 files changed, 11 insertions(+) > > diff --git a/drivers/gpu/drm/drm_colorop.c b/drivers/gpu/drm/drm_colorop.c > index fafe45b93ff8..a19e03fb9c7c 100644 > --- a/drivers/gpu/drm/drm_colorop.c > +++ b/drivers/gpu/drm/drm_colorop.c > @@ -79,6 +79,7 @@ static const char * const colorop_curve_1d_type_names[] = { > [DRM_COLOROP_1D_CURVE_BT2020_OETF] = "BT.2020 OETF", > [DRM_COLOROP_1D_CURVE_GAMMA22] = "Gamma 2.2", > [DRM_COLOROP_1D_CURVE_GAMMA22_INV] = "Gamma 2.2 Inverse", > + [DRM_COLOROP_1D_CURVE_HLG_EOTF] = "HLG", > }; > > static const struct drm_prop_enum_list > drm_colorop_lut1d_interpolation_list[] = { > diff --git a/include/drm/drm_colorop.h b/include/drm/drm_colorop.h > index ee6454b08b2d..8ec98521607d 100644 > --- a/include/drm/drm_colorop.h > +++ b/include/drm/drm_colorop.h > @@ -126,6 +126,16 @@ enum drm_colorop_curve_1d_type { > * The inverse of &DRM_COLOROP_1D_CURVE_GAMMA22 > */ > DRM_COLOROP_1D_CURVE_GAMMA22_INV, > + > + /** > + * @DRM_COLOROP_1D_CURVE_HLG_EOTF: > + * > + * enum string "HLG" > + * > + * Hybrid log-gamma transfer function. > + */ > + DRM_COLOROP_1D_CURVE_HLG_EOTF, > + Hi, if you read ITU-R BT.2100[1], you will see that the HLG EOTF has three parameters: the system gamma, the display nominal peak luminance, and the display black luminance. You cannot define a HLG EOTF or its inverse without these parameters. One might assume to derive the system gamma from the peak luminance, but I would like to leave that as a free parameter if possible, because I'm not convinced the formulas for it are universally applicable. The HLG OETF on the other hand is a fixed function. Did you mean that instead? [1]: https://gitlab.freedesktop.org/pq/color-and-hdr/-/blob/main/doc/specs.md#itu-r-bt2100 Thanks, pq
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