Graeme sketched a linearization method there:
https://lists.freedesktop.org/archives/wayland-devel/2019-March/040171.html
Sebastian prototyped there:
https://gitlab.freedesktop.org/wayland/wayland-protocols/-/merge_requests/14/commits
Thanks to Pekka for great simplifications in implementation, like the xyz_dot_prod()
Quote: "should help untangle lots of the multiplications and summations by saying
we are computing dot products, etc".
The approach was validated using matrix-shaper and cLUT type of profiles.
If profile is matrix-shaper type then an optimization is applied.
The extracted EOTF is inverted and concatenated with VCGT, if it is availible.
Introduce function cmlcms_reasonable_1D_points which would be shared between
linearization method and number of points in 1DLUT for the transform.
Co-authored-by: Pekka Paalanen <pekka.paalanen@collabora.com>
Co-authored-by: Sebastian Wick <sebastian@sebastianwick.net>
Signed-off-by: Vitaly Prosyak <vitaly.prosyak@amd.com>
The stock profile would be used when client or output
do not provide any profile or unaware of color management.
Signed-off-by: Vitaly Prosyak <vitaly.prosyak@amd.com>
1. The cmlcms_category is used to identify the purpose of transform:
- CMLCMS_CATEGORY_INPUT_TO_BLEND
- CMLCMS_CATEGORY_BLEND_TO_OUTPUT
- CMLCMS_CATEGORY_INPUT_TO_OUTPUT
2. Added following fields to cmlcms_color_profile:
- output_eotf - If the profile does support being an output profile and it
is used as an output then this field represents a light linearizing
transfer function and it can not be null. The field is null only if
the profile is not usable as an output profile. The field is set when
cmlcms_color_profile is created.
- vcgt - VCGT tag cached from output profile, it could be null if not exist
- output_inv_eotf_vcgt - if the profile does support being an output profile and it
is used as an output then this field represents a concatenation of inverse
EOTF + VCGT, if the tag exists and it can not be null.
3. Added field cmsHTRANSFORM to cmlcms_color_transform.
It is used to store LCMS optimized pipeline.
Signed-off-by: Vitaly Prosyak <vitaly.prosyak@amd.com>
Roughly speaking, a color profile describes the color space of content
or an output. Under the hood, the description includes one or more ways
to map colors between the profile space and some standard profile
connecting space (PCS).
This object is not called a color space. A color space has a unique
definition, while a color profile may contain multiple different
mappings depending on render intent. Some of these mappings may be
subjective, with an artistic touch.
When a source color profile and a destination color profile are combined
under a specific render intent, they produce a color transformation.
Color transformations are already preresented by weston_color_transform.
This patch adds the basic API for color profile objects. Everything
worthwhile of these objects is implemented in the color managers:
color-noop never creates these, and in color-lcms they are basically a
container for cmsHPROFILE, the Little CMS object for color profiles.
Color profile objects will not be interpreted outside of the color
managers, unlike color transformations.
For a start, the color manager API has one function to create color
profiles: from ICC profile data. More creation functions for other
sources will be added later.
The API has errmsg return parameter for error messages. These are not
simply weston_log()'d, because CM&HDR protocol will allow clients to
trigger errors and the protocol handles that gracefully. Therefore
instead of flooding the compositor logs, the error messages will
probably need to be relayed back to clients.
Color-lcms is expected to create a cmsHPROFILE for all kinds of color
profiles, not just for those created from ICC profile data. Hence,
color-lcms will fingerprint color profiles by the MD5 hash which Little
CMS computes for us. The fingerprint is used for de-duplication: instead
of creating copies, reference existing color profiles.
This code is very much based on Sebastian Wick's earlier work on Weston
color management, but structured and named differently.
Co-authored-by: Sebastian Wick <sebastian@sebastianwick.net>
Signed-off-by: Pekka Paalanen <pekka.paalanen@collabora.com>
Vitaly Prosyak
Pekka Paalanen